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b. Ninth reduced tube section. The ninth reduced tube section (1) is made of brass tubing and is 4 7/16 inches in length. Its upper part is a sliding fit into the bore of the lower part of the skeleton head (20, Figure 4-17). At assembly, four shallow vertical recess fiats are located on the periphery to provide clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28). The inside diameter is bored for light transmission and is provided with anti-reflection threads.

The upper part is counterbored a short distance to serve as a mount for the auxiliary upper eyepiece lens (5). It has an additional counterbored section which is threaded to receive the auxiliary upper eyepiece lens clamp ring (4). The clamp ring is secured with a lockscrew (2) which screws into the tapped hole in the upper part of this reduced tube section.

The lower part of the ninth reduced tube section (1) is counterbored with an additional counterbored and internal threaded section of 1.125 inches in length. The smooth counterbored section is a sliding fit over the upper part of the eighth reduced tube section (6) and serves as an alignment support section. The threaded part of the additional counterbored section screws vertically on the threaded periphery of the eighth reduced tube section (6) to provide the necessary vertical focusing travel of the mounted auxiliary upper eyepiece lens (5). The necessary movement of this lens in atmospheric pressure to compensate for the introduction of nitrogen is explained under Section 4U8, Step 18, and Section 4V7. The lower part of the ninth reduced tube section (1) is secured with two lockscrews (3) which are inserted into tapped holes in the upper part of the eighth reduced tube section.

c. Auxiliary upper eyepiece lens. The auxiliary upper eyepiece lens (5) is made of two optical elements, consisting of a divergent meniscus flint element cemented to a double convex crown

d. Auxiliary upper eyepiece lens clamp ring. The auxiliary upper eyepiece lens clamp ring (4) is threaded on its periphery to screw into the upper part of the ninth reduced tube section (1) to retain the auxiliary upper eyepiece lens with sufficient tension. It is kept from backing out by a lockscrew (2) protruding into the spotted recess in the threaded, periphery from the tapped hole in the ninth reduced tube section (1). The clamp ring has opposite slots in the upper face to permit it to be tightened or loosened.

e. Eighth reduced tube section. The eighth reduced tube section (6) is made of brass tubing and is 5.150 inches in length. Its inside diameter is bored for light transmission and is provided with anti-reflection threads. At assembly, the large periphery has four shallow vertical recess grooves to provide clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28). The upper part is turned to a sliding clearance fit and serves as an alignment support in the ninth reduced tube section (1).

The threaded periphery of the eighth reduced tube section is threaded an ample distance to accommodate the ninth reduced tube section clamp ring (8) and to permit the vertical focusing adjustment of the ninth reduced tube section.

The lower part of the eighth reduced tube section has a smooth counterbored section to carry the telemeter lens mount (9) which is a sliding fit. It also serves as an alignment support section for the upper alignment support section of the seventh reduced tube section (14). Two opposite air channels are located in this counterbored section for the upward passage of nitrogen. A circumferential slot with an additional circumferential recess is provided a short distance from the lower end of this counterbored section to accommodate an angular alignment lockscrew (7). It is used to permit angular adjustment of the telemeter lens mount during collimation, so that the telemeter lens line lies in a true vertical plane. The circumferential alignment lockscrew extends through the circumferential slot into a

f. Ninth reduced tube section clamp ring. The ninth reduced tube section clamp ring (8) is made of nominal thickness and width. The inside diameter is threaded to screw on the threaded periphery of the upper part of the eighth reduced tube section, and is provided with two opposite drilled holes to accommodate a special spanner wrench. This clamp ring screws up tightly against the lower face of the ninth reduced tube section after its final adjustment and is secured with a lockscrew (11). This lockscrew extends into a tapped hole in the threaded periphery of the eighth reduced tube section. After assembly the clamp ring is provided with four shallow vertical flat faces to allow clearance for the prism tilt and change of power shifting tapes (38, Figure 4-28).

g. Telemeter lens. The telemeter lens (13) is made of one flint plano convex element. The plano surface is etched with vertical and horizontal calibrations in degrees of true field, and provides a means of measuring the angular size of a target. Refer to Section 4U7, Paragraph (a) for further detail.

The telemeter lens is placed in the image plane of the auxiliary upper telescope, and the first real image plane of the periscope, so that the graduations appear to vibrate in unison with the image and observation is easier.

The telemeter lens periphery is provided with a stoned vertical recess groove for the protruding lockscrew of the telemeter lens mount (9), thus permitting it to be reassembled in its original position, and preventing any angular, shift of the telemeter lens in the mount. The plano surface of the lens is placed toward the seat of the mount

h. Telemeter lens mount. The telemeter lens mount (9) is made of brass tubing and is 0.562 inch in width. Its inside diameter is bored for light transmission and threaded for anti-reflection. The mount is a sliding fit in the smooth counterbored section in the lower part of the eighth reduced tube section (6), and is secured after collimation with the circumferential alignment lockscrew (7). The mount is counterbored to carry the telemeter lens (13) and the telemeter lens clamp ring (10). The mount is provided with a small screw located as a permanent fitting and filed off so that the protruding section of the screw allows the free disassembly and reassembly of the telemeter lens in the mount. This protruding section of the screw, when engaged in the stoned vertical recess groove of the telemeter lens periphery, prevents it from shifting angularly in the mount and also provides the original reassembly of the lens in the mount. Two opposite drilled holes are provided in the lower part of the mount to receive a special tool which is used to remove the mount from the eighth reduced tube section.

i. Telemeter lens clamping. The telemeter lens clamp ring (10) is made of brass tubing and is of nominal thickness and width. It is a push fit in the counterbored section of the telemeter lens mount (9). This clamp ring fits snugly against the convex surface of the telemeter lens, and is secured with two opposite lockscrews (12). These lockscrews extend into tapped holes in the upper part of the telemeter lens mount and into the partially tapped hole of each clamp ring.

j. Seventh reduced tube section. The seventh reduced tube section (14) is made of brass tubing and is 8.161 inches in length. At assembly it is provided with four shallow vertical recess grooves the entire length to allow sufficient clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28). The upper part is machine-turned to serve as an alignment support section, and is a sliding fit in the small counterbored section in the lower part of the eighth reduced tube section (6). The threaded periphery section in the upper part receives the counterbored threaded section in the lower part of the eighth reduced tube section (6) and is secured with four lockscrews (11). These lockscrews are

The inside diameter is bored for light transmission and threaded for anti-reflection. The lower part of the seventh reduced tube section has a counterbored threaded section of 1 1/16 inches. This counterbored threaded section serves as a mount for the auxiliary upper objective lens (18), and is secured with two auxiliary upper objective lens clamp rings (15). One clamp ring serves as a seat for the flint element of the lens doublet in the upper part of this section, while the second clamp ring secures snugly against the crown element of the lens doublet in the lower part of this section. Each clamp ring is secured with a lockscrew (17). Two opposite shallow vertical grooves in the threaded wall of this section provide for nitrogen passage.

An additional counterbore of 1.157 inches in length is provided to serve as an alignment support section with the lower part of 0.340-inch length of this section threaded. This threaded section screws on the threaded periphery of the sixth reduced tube section (1, Figure 4-19) of the auxiliary lower telescope system and is secured with four lockscrews (16). These lockscrews extend into countersunk clearance holes and into tapped holes in the alignment support section of the sixth reduced tube section.

k. Auxiliary upper objective lens. The auxiliary upper objective lens (18) is made of two optical elements, consisting of a divergent meniscus flint element cemented to a double convex crown element, forming a positive doublet. It is mounted in the threaded counterbore section in the lower part of the seventh reduced tube section (14) with two auxiliary upper objective lens clamp rings (15) located on opposite sides of the lens.

l. Auxiliary upper objective lens clamp rings. The auxiliary upper objective lens clamp rings (15) are made of brass tubing and are of nominal thickness and width. Both clamp rings are identical, with the periphery threaded, and

One clamp ring is inserted into the threaded counterbore in the lower part of the seventh reduced tube section before insertion of the auxiliary upper objective lens (18). The second clamp ring contacts the lower side of the objective lens. Each clamp ring is secured with a lockscrew (17), which extends into the countersunk clearance hole in the dower part of the seventh reduced tube section (14) and into the tapped hole in each clamp ring.

4G2. Disassembly of the seventh, eighth, and ninth reduced tube sections. The seventh, eighth, and ninth reduced tube sections are disassembled in the following manner:

1. Remove the two lockscrews (11) from the lower part of the eighth reduced tube section 6). These lockscrews are unscrewed from tapped holes in the upper part of the external alignment support section of the seventh reduced tube section (14).

2. Unscrew the seventh reduced tube section 14) from the eighth reduced tube section (6).

3. Remove the two lockscrews (17) from the lower part of the seventh reduced tube section. These lockscrews are unscrewed from tapped holes in the two auxiliary upper objective lens clamp rings (15).

4. Remove the lower clamp ring (15), unscrewing it with a special wrench from the lower part of the seventh reduced tube section.

5. The auxiliary upper objective lens (18) slides out easily. This is done by turning this reduced tube section on its lower end over clean lens tissue, and tapping, around the periphery with a light rawhide mallet. Make certain that the lens drops lightly on soft lens tissue.

6. Unscrew the upper clamp ring (15) in the same manner as noted under Step 4.

7. Remove the two lockscrews (3) from the lower part of the ninth reduced tube section (1).

8. Unscrew the ninth reduced tube section (1) from the eighth reduced tube section (6).

9. Remove the lockscrew (11) from the ninth reduced tube section clamp ring (8). This

10. Remove the circumferential alignment lockscrew (7). This lockscrew is unscrewed from the tapped hole in the telemeter lens mount (9), and is removed from the circumferential slot in the eighth reduced tube section.

11. Remove the telemeter lens mount (9) from the lower part of the eighth reduced tube section. This is done by means of a special pair of calipers. The two rounded ends of the calipers fit into opposite drilled holes in the lower part of the mount.

12. Remove the two lockscrews (12) from opposite sides of the telemeter lens mount (9). These lockscrews are unscrewed from tapped holes in the telemeter lens clamp ring (10).

13. Turn the telemeter lens mount (9) with its upper face on a piece of lens tissue. If necessary, using a piece of lens tissue, press downward on the upper side of the telemeter lens (13), removing both the lens and the clamp ring (10). Wrap the lens in clean lens tissue and store in a box to prevent scratches and breakage.

14. Remove the lockscrew (2) from the upper part of the ninth reduced tube section (1). This lockscrew is unscrewed from the tapped hole in the auxiliary upper eyepiece lens clamp ring (4).

15. Unscrew the auxiliary upper eyepiece lens clamp ring (4), using a special wrench.

16. Place the upper end of the ninth reduced tube section on a piece of lens tissue. If necessary, tap lightly on the periphery of this reduced tube section with a small rawhide mallet. The auxiliary upper eyepiece lens (5) should slide out easily.

17. Wrap all lenses in clean lens tissue and place to one side, to prevent scratches and breakage.

4G3. Reassembly of the seventh, eighth, and ninth reduced tube sections. The seventh, eighth, and ninth reduced tube sections are reassembled in the following manner:

1. Using an air line pressure hose, blow out the internal surfaces of the seventh reduced

2. Place the upper clamp ring (15) in the threaded counterbored section in the lower part of the seventh reduced tube section and screw it in until the lockscrew holes coincide.

3. Insert and secure the lockscrew (17) in the countersunk clearance hole in the lower part of the seventh reduced tube section and screw it into a tapped hole in the upper clamp ring (15).

4. Clean the auxiliary upper objective lens (18) with clean lens tissue. Surface dust can be removed with a rubber air bulb and a camel's hair brush. A vacuum brush used with ether is also effective.

5. Place the objective lens of this system in the lower part of the seventh reduced tube section, turning the flint side of the lens doublet toward the lower face of the upper clamp ring (15).

6. Place the lower clamp ring (15) in the same threaded counterbored section on the lower face or crown side of the objective lens. Screw this clamp ring tightly against the objective lens with a special wrench. The lockscrew holes should coincide when this lens is tightened sufficiently.

7. Insert and secure the lockscrew (17) in the countersunk clearance hole in the lower part of the seventh reduced tube section and screw it into a tapped hole in the lower clamp ring (15).

8. Place the ninth reduced tube section clamp ring (8) on the threaded periphery of the eighth reduced tube section (6), screwing it beyond its locking position.

9. Clean the telemeter lens (13) in similar manner to that outlined under Step 4.

10. Place the telemeter lens (13) in the telemeter lens mount (9) with the etched graduations resting against the shoulder of the mount, and the stoned vertical recess groove meshing with the inward protruding screw in the mount.

12. Insert and secure the two lockscrews (12) in the tapped holes in the mount and clamp ring (10).

13. Slide the telemeter lens (13) with its mount (9) into the lower part of the eighth reduced tube section with the etched graduated surface facing the lower part of this reduced tube section and the curvature facing upward.

14. Insert the circumferential alignment lockscrew (7) through the circumferential slot in the lower part of the eighth reduced tube section. This lockscrew extends into the tapped hole in the telemeter lens mount (9).

15. Screw the lower part of the eighth reduced tube section (6) on the upper part of the seventh reduced tube section (14) until the lockscrew holes coincide. The upper face of the seventh reduced tube section almost contacts the lower face of the telemeter lens mount, and prevents axial movement of the mount.

16. Secure the seventh and eighth reduced tube sections with four lockscrews (11). These lockscrews are inserted in countersunk clearance holes in the eighth reduced tube section and screwed into tapped holes in the upper part of the alignment support section of the seventh reduced tube section.

17. Clean the auxiliary upper eyepiece lens (5) in similar manner to that outlined in Step 4.

18. Place the auxiliary upper eyepiece lens in the seat of the upper part of the ninth reduced tube section with the crown side of the lens doublet against the seat of this section.

19. Screw the auxiliary upper eyepiece lens clamp ring (4) into and against the lens tightly to insure that the tapped holes coincide.

20. Place the lockscrew (2) in the tapped holes in both the ninth reduced tube section (1) and the clamp ring (4) for securement.

21. Place an auxiliary telescope at the lower part of the seventh reduced tube section. Set the auxiliary telescope diopter at infinity for the observer. (This setting should be based on

22. Screw the lower part of the ninth reduced tube section (1) onto the upper part of the eighth reduced tube section (6).

23. With the use of an infinity target, primary collimation of this auxiliary upper telescope system is carried out in the following manner. The ninth reduced tube section is moved downward, focusing the auxiliary upper eyepiece lens until the image of the target is apparent on the telemeter lens. At this setting, the auxiliary telescope is focused from plus

24. This auxiliary upper telescope system, being of unit power magnification, requires the use of an auxiliary telescope to set the system to zero diopter. This constitutes the primary collimation of this telescope system. Any error in this telescope system when assembled to the rest of the instrument is apparent when magnified at 6 power.

25. Keep the lockscrews (3) which secure the ninth reduced tube section (1) to the eighth reduced tube section (6) and the ninth reduced tube section clamp ring lockscrew (11) in a small box until the final collimation on a distance target of 1200 feet at atmospheric pressure is completed.

a. Sections. The auxiliary lower telescope system consists of five reduced tube sections of a unit power telescope which make up the necessary length and carry six parts which locate the lenses in appropriate relation to their focal lengths. The system consists of the second, third, fourth, fifth, and sixth reduced tube sections,

b. Sixth reduced tube section. The sixth reduced tube section (1) is made of brass tubing

The upper part is turned a sliding fit and serves as an alignment support section in the counterbored alignment support section in the lower part of the seventh reduced tube section. The threaded periphery section in the upper part of this reduced tube section receives the counterbored threaded section in the lower part of the seventh reduced tube section (14, Figure 4-18) and is secured with four lockscrews (16) of the auxiliary upper telescope system assembly.

The lower part is turned a sliding fit and serves as an alignment support section in the counterbored alignment support section in the upper part of the fifth reduced tube section (2). The threaded periphery section in the lower part screws into the threaded counterbore in the upper part of the fifth reduced tube section, and is secured with four lockscrews (6) which are inserted into countersunk clearance holes in the upper part of the fifth reduced tube section (2) and screwed into tapped holes in the lower alignment support section of the sixth reduced tube section (1). The lower part has a shoulder 1/4 inch wide and its diameter coincides with the diameter of the upper part of the fifth reduced tube section.

c. Fifth reduced tube section. The fifth reduced tube section (2) is made of brass tubing, and is 7.187 inches in length. The upper part of its external wall is straight turned a distance of 4 inches. A taper guide is located on this surface with a center distance of approximately 2 1/4 inches from the upper face and is secured to this reduced tube section with four lockscrews (7). From the 4-inch turned section, the lower part of this reduced tube section is tapered outward for 1 15/16 inches at which point there is a shoulder 1/8 inch wide. The diameter of this shoulder coincides with the diameter of the upper part of the fourth reduced tube section (9). The part below the large shoulder is straight turned a short

This reduced tube section is bored to a diameter of 0.946 inch for light transmission. The lower part is counterbored with a taper, which tapers inward from the lower end and upward for a distance of 3 15/16 inches. From this point it remains a straight counterbored section for a distance of 2 3/16 inches. The tapered and straight counterbored sections are provided with anti-reflection threads. This reduced tube section tapers principally to allow sufficient space, and to form a wall around the marginal or oblique light ray bundles. These bundles diverge downward from the auxiliary lower objective lens (8), through the fourth reduced tube section (9) to the auxiliary lower eyepiece lens (18) of the third reduced tube section (12).

The upper part of the fifth reduced tube section is counterbored an appropriate distance to serve as a mount for the auxiliary lower objective lens (8) with an internal threaded section to accommodate the auxiliary lower objective lens clamp ring (3). Two opposite shallow air channels located in the inner wall of this mount section and protruding into the seat of the mount permit passage of the charging nitrogen. An additional counterbored section serves as an alignment support section with an internal threaded section above it to receive the upper alignment support section and the threaded periphery of the 6th reduced tube section (1).

d. Taper guide. The taper guide (4) is made of brass tubing, with a nominal wall thickness, and is 5/8 inch in width. The upper part is tapered slightly at assembly to allow about 0.005 inch clearance on the diameter with the inside wall of the outer taper section (1, Figure 4-15). The bore of the taper guide is a push fit on the upper part of the fifth reduced tube section (2). The inside

e. Auxiliary lower objective lens. The auxiliary lower objective lens (8) is identical to the auxiliary upper objective lens (18, Figure 4-18) of the auxiliary upper telescope system. The flint element of this doublet is secured against the shoulder seat in the fifth reduced tube section by means of a threaded auxiliary lower objective lens clamp ring (3) which is secured with a lockscrew (5).

f. Auxiliary lower objective lens clamp ring. The auxiliary lower objective lens clamp ring (3) is identical to the auxiliary upper objective lens clamp rings (15, Figure 4-18) of the auxiliary upper telescope system. The clamp ring is inserted in the threaded counterbore in the lower part of the fifth reduced tube section, and contacts the crown element side of the auxiliary lower objective lens to secure the lens doublet snugly. The clamp ring is secured from unscrewing by the insertion of a lockscrew (5) which is inserted into a countersunk clearance hole in the lower part of the fifth reduced tube section and screwed into a tapped hole in the clamp ring.

g. Fourth reduced tube section. The fourth reduced tube section (9) is made of brass tubing, and is 7.937 inches in length. Its external diameter is tapered, with the inside diameter tapered in the same proportion allowing the wall a nominal thickness. It is provided with antireflection threads.

The lower part of the fourth reduced tube section has a shoulder 3/16 inch in width, located at the lower part of the taper. Its diameter coincides with the diameter in the upper part of the third reduced tube section (12). Below this shoulder, the lower part is turned straight, and is provided with an alignment support section and threaded periphery. The alignment support section is a sliding fit in the upper counterbored alignment section in the third reduced tube section, while

The upper part is counterbored straight a depth of 1.130 inches, to serve as an alignment support section with a portion threaded to receive the alignment support section and threaded periphery in the lower part of the fifth reduced tube section. In the upper part a 1/8-inch diameter hole is drilled through the wall and is located 1.571 inches from the upper end, for the assembly of an air line adapter (11).

h. Air line adapter. The air line adapter (11) consists of a piece of flat brass air line, with the upper end closed, provided with a 1/8-inch diameter drilled hole located 7/64 inch from the upper end. The adapter is soldered to the periphery in the upper part of the fourth reduced tube section (9) with 1/8-inch holes in coincidence. The lower opening of the adapter receives the air line section (18) shown on the upper telescope system Part I assembly (Figure 4-20).

i. Third reduced tube section. The third reduced tube section (12) is made of brass tubing and is 3.562 inches in length. It is bored straight for light transmission, and carries the auxiliary lower eyepiece lens mount (13) which is a sliding axial fit in its central part.

Its external diameter is a step larger than the preceding reduced tube section, and it has a large shoulder 1/8 inch in width. This shoulder forms a flange, with a diameter that coincides with the diameter of the upper part of the second reduced tube section (19). The part below the shoulder flange is turned straight, with a threaded periphery and an alignment support section. The alignment support section is a sliding fit into the counterbored alignment support section in the upper part of the second reduced tube section, while its threaded periphery screws into the internal threaded section in the same counterbored section. It is secured with four lockscrews (20) which are inserted into countersunk clearance holes in the upper part of the second reduced tube section and

The center part of this reduced tube section has opposite axial slots of appropriate length in which the auxiliary lower eyepiece lens (18) and its mount (13) are focused in the primary and final collimation of the auxiliary upper and lower telescope system.

The bore of the upper part is provided with a partially threaded section to receive the threaded periphery of the lower part of the fourth reduced tube section, while the bore serves as an alignment support section for the lower alignment support section of the fourth reduced tube section.

The lower part is counterbored a depth of 1.125 inches upward to provide clearance for light transmission and to lighten the reduced tube section. The air line section (18) shown on the upper telescope system Part I (Figure 4-20) extends downward from the fourth reduced tube section over this reduced tube section.

j. Auxiliary lower eyepiece lens. The auxiliary lower eyepiece lens (18) is made of two optical elements, consisting of a double convex crown element cemented to a divergent meniscus flint element, forming a positive doublet. It is mounted in the auxiliary lower eyepiece lens mount (13) with the flint element resting in the seat of the counterbored section of the mount, and is secured with an auxiliary lower eyepiece lens clamp ring (14) which is secured with a lockscrew (16).

k. Auxiliary lower eyepiece lens mount. The auxiliary lower eyepiece lens mount (13) is made of brass tubing, and is 0.780 inch in length. It is bored for light transmission, and is provided with two counterbored sections. The small counterbored section carries the auxiliary lower eyepiece lens (18), while the large counterbored section is threaded to receive the auxiliary lower eyepiece lens clamp ring (14) which is secured with a lockscrew (16). The mount is a sliding fit in the bore of the third reduced tube section, and is moved axially to focus the auxiliary lower eyepiece lens (18) for fine

Two opposite narrow air channels in the periphery permit passage of charging nitrogen. A tapped hole is provided to receive a screw which is inserted temporarily through the axial slot of the third reduced tube section during collimation, to focus the mount axially, thus carrying the auxiliary lower eyepiece lens (18) vertically for adjustments required.

The face of the mount is beveled inward at 45 degrees to prevent restriction to the light rays that are deflected downward. The mount is secured with two lockscrews (17) which are inserted into countersunk clearance holes in the third reduced tube section and screwed into tapped holes in the mount. Two opposite drilled holes are provided in the upper wall of the mount to receive a special tool which is used to remove the mount from the third reduced tube section.

l. Auxiliary lower eyepiece lens clamp ring. The auxiliary lower eyepiece lens clamp ring (14) is made of brass tubing and is of nominal thickness and width. The periphery is threaded to screw into the threaded counterbore of the auxiliary lower eyepiece lens mount (13) to secure the lens. The upper face of the clamp ring is beveled at 30 degrees with a matching inside bevel from an undercut groove of the bore, thus providing a 1/64-inch upper wall to secure the lens sufficiently and a shock support to the crown element of the lens. The remaining bore is tapered outward. Two opposite slots are provided in the side face of the clamp ring for the insertion of a special wrench. The clamp ring is secured with a lockscrew (16) which is inserted in a countersunk hole in the mount and screwed into a tapped hole in the clamp ring.

m. Second reduced tube section. The second reduced tube section (19) is made of brass tubing, and is 16.300 inches in length. It serves to enclose the light rays to the designed clear aperture area, and to provide the necessary distance between the auxiliary lower telescope system and the upper telescope system assembly Part I. Its outside diameter is uniform for its entire length, with the exception of the lower part. This part has a shoulder flange 3/16 inch in width, the outside diameter coinciding

The lower part below the shoulder flange is turned to serve as an alignment support section and is a sliding fit in the counterbored alignment support section in the first reduced tube section (1, Figure 4-20). The threaded periphery screws into the threaded section of the same counterbore. It is secured with four lockscrews (8) which are inserted in countersunk clearance holes in the upper part of the first reduced tube section (1, Figure 4-20) and screwed into tapped holes in the lower alignment support section of the second reduced tube section (19).

The inside diameter is bored for light transmission and is provided with anti-reflection threads up to the upper alignment support section. The bore in the upper part serves as an alignment support section and is threaded above the upper part, to receive the lower alignment support section and the threaded periphery of the third reduced tube section (12).

The air line section (18, Figure 4-20) of the upper telescope system assembly Part I, extends downward the entire length of this reduced tube section. It is secured to it with a removable air line strap (21) which is secured with two lockscrews (22). These lockscrews are inserted in clearance holes in the air line strap (21) and screwed into tapped holes in the wall of this reduced tube section.

4H2. Disassembly of the second, third, fourth, fifth, and sixth reduced tube sections. The second, third, fourth, fifth, and sixth reduced tube sections are disassembled in the following manner:

1. Remove the four lockscrews (6) from the upper part of the fifth reduced tube section (2). These lockscrews are unscrewed from tapped holes in the lower alignment support section of the sixth reduced tube section (1).

2. Unscrew the sixth reduced tube section (1) from the fifth reduced tube section (2).

3. Remove the lockscrew (5) from the upper part of the fifth reduced tube section (2). This

4. Using a special wrench, unscrew the clamp ring (3).

5. Place the upper end of the fifth reduced tube section (2) on a piece of clean lens tissue, allowing the auxiliary lower objective lens (8) to slide out.

6. Remove the four lockscrews (7) from the taper guide (4). These lockscrews are unscrewed from tapped holes in the wall of the fifth reduced tube section (2).

7. Carry the taper guide (4) off the upper part of the fifth reduced tube section (2).

8. Remove the four lockscrews (10) from the upper part of the fourth reduced tube section. These lockscrews are unscrewed from the tapped holes in the lower alignment support section of the fifth reduced tube section (2).

9. Unscrew the fifth reduced tube section (2) from the upper part of the fourth reduced tube section (9).

10. Remove the four lockscrews (15) from the upper part of the third reduced tube section (12). These lockscrews are unscrewed from the tapped holes in the lower alignment support section of the fourth reduced tube section (9).

11. Unscrew the fourth reduced tube section (9) from the upper part of the third reduced tube section (12).

12. Remove the two lockscrews (17) from the central part of the third reduced tube section (12). These lockscrews are unscrewed from tapped holes in the auxiliary lower eyepiece lens mount (13).

13. Turn the assembled third and second reduced tube sections so that the third reduced tube section is facing downward. Tap lightly on the periphery of the third reduced tube section (12) with a light rawhide mallet. The assembled auxiliary lower eyepiece lens (18) and its mount (13) with the clamp ring (14) should slide out easily.

14. Remove the lockscrew (16) from the periphery of the auxiliary lower eyepiece lens mount (13), unscrewing it from the tapped hole in the clamp ring (14).

16. Place the upper end of the mount (13) on a piece of clean lens tissue. The auxiliary lower eyepiece lens (18) should drop out easily. If difficulty should be encountered, place a piece of clean lens tissue over the mount and push downward.

17. Remove the four lockscrews (20) from the upper part of the second reduced tube section (19). These lockscrews are unscrewed from tapped holes in the lower alignment support section of the third reduced tube section (12).

18. Unscrew the third reduced tube section (12) from the upper part of the second reduced tube section (19).

19. Place the lens doublets of this telescope system to one side, to prevent scratches or breakage.

4H3. Reassembly of the second, third, fourth, fifth, and sixth reduced tube sections. The second third, fourth, fifth, and sixth reduced tube sections are reassembled in the following manner:

1. Using an air hose, blow out the internal surface of the sixth reduced tube section. If a circular brush is available, it should be used before the air hose. This procedure is carried out with each reduced tube section of this assembly, and also with the clamp rings and lens mounts.

2. Clean the auxiliary lower objective lens (8) with clean lens tissue. Surface dust can be removed with a rubber air bulb and a camel's hair brush; a vacuum brush used with ether is also effective.

3. Place the objective lens of this system in the upper part of the fifth reduced tube section (2). The lens doublet should be placed so that the flint element is resting against the seat of the mount section.

4. Place the clamp ring (3) in the threaded counterbored section of the upper part of the fifth reduced tube section (2). Screw the clamp ring tight against the crown element of the lens doublet. The lockscrew holes should coincide when this lens is tightened sufficiently.

6. Assemble the taper guide (4) over the upper part of the fifth reduced tube section (2). Push this taper guide on, noting the reference numerals to determine its correct assembly with the lockscrew holes. The tapered part faces upward.

7. Insert and secure the four lockscrews (7). These lockscrews are inserted in countersunk clearance holes in the taper guide (4) and screwed into tapped holes in the periphery of the fifth reduced tube section (2).

8. Insert the threaded periphery of the lower part of the sixth reduced tube section (1) in the threaded counterbored section in the upper part of the fifth reduced tube section (2). Screw it tight until the lockscrew holes coincide.

9. Secure the sixth and fifth reduced tube sections with the four lockscrews (6). These lockscrews are inserted in countersunk clearance holes in the fifth reduced tube section and screwed into tapped holes in the lower alignment support section of the sixth reduced tube section.

10. Insert the threaded periphery of the lower part of the fifth reduced tube section (2) in the threaded counterbored section in the upper part of the fourth reduced tube section (9). Screw it tight until the lockscrew holes coincide.

11. Secure the fifth and fourth reduced tube sections with four lockscrews (10). These lockscrews are inserted in countersunk clearance holes in the upper part of the fourth reduced tube section (9) and screwed into tapped holes in the lower alignment support section of the fifth reduced tube section (2).

12. Clean the auxiliary lower eyepiece lens (18) in similar manner to that described in Step 2.

13. Place the auxiliary eyepiece lens (18) in the mount (13) so that the flint element of this lens doublet rests in the seat of the mount.

14. Place the clamp ring (14) in the threaded counterbored section in the mount. Using a special wrench, screw the clamp ring tight against the crown element of this lens doublet. The lockscrew

15. Insert and secure the lockscrew (16) in the countersunk clearance hole in the mount (13) and screw it into the tapped hole in the clamp ring (14).

16. Slide the mounted auxiliary lower eyepiece lens (18) with the mount (13) into place in the central part of the third reduced tube section (12). Place the mount so that the clamp ring side remains toward the upper part. Insert the one lockscrew (17) temporarily to hold the mount in place.

17. The auxiliary lower eyepiece lens mount (13) is not secured with the two lockscrews (17) during the primary collimation of the auxiliary lower telescope system. The lockscrews should be placed in a small box until the final collimation is completed.

18. Place the upper part of the third reduced tube section (12) on the lower alignment support section of the fourth reduced tube section (9), screwing it on the threaded periphery.

19. Secure the fourth and third reduced tube sections (9 and 12) with four lockscrews (15). These lockscrews are inserted into countersunk clearance holes in the upper part of the third reduced tube section (12) and screwed into tapped holes in the lower alignment support section of the fourth reduced tube section.

20. Insert the threaded periphery of the lower part of the third reduced tube section (12) into the threaded counterbore of the upper part of the second reduced tube section (19).

21. Secure the third and second reduced tube sections (12 and 19) with four lockscrews (20). These lockscrews are inserted into countersunk clearance holes in the upper part of the second reduced tube section (19) and screwed into tapped holes in the lower alignment support section of the third reduced tube section.

22. Assemble the auxiliary lower telescope system assembly to the auxiliary upper telescope system assembly. Insert the threaded periphery of the upper part of the sixth reduced tube section (1) into the threaded counterbore of the lower part of the seventh reduced tube section (14, Figure 4-18).

24. Place an auxiliary telescope at the lower end of the second reduced tube section. Set the auxiliary telescope diopter at infinity for the observer. (This setting should be based on at least five observations of an infinity target which give consistent readings.)

25. Move the auxiliary lower eyepiece lens in until the image of the infinity target is apparent on the telemeter lens. The movement of the auxiliary lower eyepiece lens requires fine movement, as the image is lost with very little movement.

26. Focus the auxiliary telescope from plus to observe the diopter reading, taking a series of observations to determine the correct setting of the auxiliary lower eyepiece lens. This telescope system, being of unit power magnification, requires the use of an auxiliary telescope to set the system to zero diopter. This constitutes primary collimation of the auxiliary lower telescope system to the auxiliary upper telescope system.

27. Any error in the auxiliary lower telescope system, when assembled to the rest of the instrument, is apparent when magnified at 6 power. This error can be compensated during final collimation.

The upper telescope system is divided principally to permit familiarization as to nomenclature, description, disassembly, and reassembly. It is composed of three lenses, namely: a positive upper eyepiece lens doublet, a plano convex collective, lens, and an air space upper objective lens doublet. This system is used in reverse to decrease the lower telescope system to a 6 power magnification.

Part I: a. First reduced tube section and fifth and sixth inner tube sections. Figure 4-20 shows the upper telescope system assembly Part I. All bubble numbers in Section 4I1, 3 and 4 refer to Figure 4-20 unless otherwise specified.

b. First reduced tube section. The first reduced tube section (1) is made of cast phosphor bronze, and is 18.750 inches in length. It serves to enclose the marginal or oblique light rays diverging downward from the upper eyepiece lens in the upper part to the collective lens in the lower part. The external diameter tapers from the upper part downward to the shoulder flange in the lower part.

The shoulder flange is 3/16 inch in width, with the outside diameter coinciding with the diameter of the upper part of the reducing coupling (2). In the lower part below the shoulder flange is a turned section serving as an alignment support section for insertion in the upper part of the reducing coupling (2). The threaded periphery screws into the threaded part of the same counterbored section and is secured with four lockscrews (12). These lockscrews are inserted in countersunk clearance holes in the upper part of the reducing coupling and screwed

The upper part is counterbored straight for a depth of 3.062 inches and carries the mounted upper eyepiece lens (20) and mount (6). An axial slot of appropriate length is provided in the wall near the lower part of the counterbored section for the insertion of a screw in the tapped hole in upper eyepiece lens mount (6). The upper eyepiece lens (20) can be focused vertically with its mount during primary and final collimation of the upper and lower telescope systems.

An additional counterbore of 1.250 inches in length serves as an alignment support section to receive the alignment support section in the lower part of the second reduced tube section (19, Figure 4-19), while the threaded section of this counterbored section receives the threaded periphery of the second reduced tube section (19). It is secured with four lockscrews (8) which are inserted in countersunk clearance holes in the upper part of the first reduced tube section (1) and screwed into tapped holes in the lower alignment support, section of the second reduced tube section (19, Figure 4-19).

The internal diameter tapers upward from the counterbored section in the lower part to the small counterbored section in the upper part, and is provided with anti-reflection threads. The lower part is counterbored a depth of 1 5/16 inches, and is threaded to receive the collective lens mount (3) and the threaded section of the diaphragm (13).

The lower part of this reduced tube section is provided with an air line strap (19) to retain the bent air line (17). It is secured with two lockscrews (22) which are inserted in clearance holes in the air line strap and screwed into tapped holes in the wall of the first reduced tube section (1). The air line section (18) extends downward from the preceding reduced tube section to the lower part. At this point the soldered air line coupling (14) soldered to its lower part connects in the upper part of the bent air line (17).

The bent air line (17) extends over the reducing coupling (2) and has a soldered flat air line coupling (15) at its lower part. The flat air line coupling (15) has a short air line section (16) soldered to its lower part. This short air line

c. Upper eyepiece lens. The upper eyepiece lens (20) is made of two optical elements, consisting of a plano concave flint element cemented to a double convex flint element, forming a positive doublet. It is mounted in the upper eyepiece lens mount (6) with the curvature surface of the doublet resting against the seat of the mount and is secured with an upper eyepiece lens clamp ring (5) and a lockscrew (9).

d. Upper eyepiece lens mount. The upper eyepiece lens mount (6) is made of brass tubing and is 1.120 inches in length. It has two counterbored sections. The smaller smooth turned counterbored section carries the upper eyepiece lens doublet (20). The larger counterbored section is threaded to receive the threaded periphery of the upper eyepiece lens clamp ring (5). The upper face is chamfered from the bore at a 45 degrees angle outward. The mount is a sliding fit in the small counterbored section in the upper part of the first reduced tube section (1). The mount is moved vertically during collimation by a temporarily inserted screw extending through the axial slot of the first reduced tube section into a tapped hole in the mount. This vertical focusing of the upper eyepiece lens (20) is necessary to obtain correct adjustment for definition and to eliminate parallax in the upper and lower telescope system during primary and final collimation. The mount is secured in the first reduced tube section (1) with two lockscrews (10). These lockscrews are inserted in countersunk clearance holes in the reduced tube section and screwed into tapped holes in the mount. Two opposite narrow vertical air channels are provided in the periphery of the mount to allow sufficient clearance for the passage of nitrogen.

e. Upper eyepiece lens clamp ring. The upper eyepiece lens clamp ring (25) is made of brass tubing, and is of nominal thickness and width. The periphery is threaded to screw into the threaded counterbored section in the upper eyepiece lens mount (6) to secure the lens doublet. The upper face of the clamp ring is chamfered at a 30 degrees angle outward from the bore, with a matching inside chamfer from the undercut groove of the bore. This provides a 1/64-inch

f. Collective lens. The collective lens (21) is made of one plano convex crown optical element. Refer to Section 4U8 Step 10 for further detail. The plano side of the lens rests against the seat in the collective lens mount (3) and is secured with a collective lens clamp ring (4) which is secured with a lockscrew (11).

g. Collective lens mount. The collective lens mount (3) is made of brass tubing of nominal thickness and width. Its periphery is threaded to screw into the threaded counterbored section in the lower part of the first reduced tube section (1). The mount has two counterbored sections. The smaller counterbored section carries the collective lens (21) and the larger is threaded to carry the clamp ring (4). The upper face of the mount is chamfered at a 45 degrees angle outward from the bore. The mount is secured with a lockscrew (7). This lockscrew is inserted in a tapped hole in the lower alignment support section of the first reduced tube section (1) and screwed into the partially tapped hole in the mount. Two opposite narrow air channels are provided in the periphery of the mount to allow sufficient clearance for nitrogen passage.

h. Collective lens clamp ring. The collective lens clamp ring (4) is made of brass tubing material of nominal thickness and width. The periphery is threaded to screw into the larger threaded counterbored section in the collective lens mount (3) to secure the lens. The upper face of the clamp ring is chamfered at a 30 degrees angle outward from the bore, with a matching inside chamfer from the undercut groove of the bore. This provides a 1/64-inch upper wall to secure the lens sufficiently and also provides a shock support to the curvature face of the collective lens. Two opposite slots are provided in the lower face of the clamp ring for the insertion of a special wrench. The clamp is secured in the mount with a lockscrew (11). This lockscrew is

i. Diaphragm. The diaphragm (13) is made of brass tubing and is 1.868 inches in length. It confines the light rays to the required aperture area, thus preventing any unwanted reflection of light which might result from striking the walls of the next inner tube section. The outer diameter is threaded a distance of 1/2 inch with the remaining section smooth turned below the root diameter of the threaded section.

It is bored for light transmission, with a counterbore provided with anti-reflection threads. The 0.060-inch shoulder in the lower part is chamfered at a 45 degrees angle outward from the bore.

j. Reducing coupling. The reducing coupling (2) is made of cast phosphor-bronze material. Its lower part is designed to fit in the sixth inner tube section upper end coupling (26), while its upper part has a reduction which carries the lower part of the first reduced tube section (1). It has a large bearing flange 1/16 inch wide, and its diameter is a few thousandths of an inch smaller than the inner diameter of the outer tube. This flange serves as a bearing to stabilize the reduced tube sections and the upper part of the sixth inner tube section (23) in the outer tube (2, Figure 4-15). The reducing coupling is bored for light transmission, and has a threaded section in the upper part of the bore to receive the threaded periphery of the lower part of the first reduced tube section (1). The smooth part of the bore serves as an alignment support section for the lower alignment support section of the first reduced tube section (1). The reduced diameter of the upper part of this coupling has sufficient wall thickness for stabilization of the reduced tube sections above it. The first reduced tube section (1) and the reducing coupling (2) are secured with four lockscrews (12). These lockscrews are inserted in countersunk clearance holes in the upper part of the reducing coupling and screwed into tapped holes in the lower alignments support section of the first reduced tube section.

The lower part of the reducing coupling below the bearing flange is smooth turned to serve as an alignment support section with a threaded periphery in the upper part. It is a sliding fit in

The bearing flange has four vertical slots, two opposite the others to provide clearance for the prism tilt and power shifting wire tapes (38, Figure 4-28). An air line slot is provided at right angles to, the tape slots at assembly in the bearing flange for the air line coupling (15).

k. Sixth inner tube section. The sixth inner tube section (23) is made of brass tubing and is 75 1/2 inches in length. Its inner and outer diameter are uniform the entire length. An air line section (30) of 71 3/8 inches in length is soldered on its periphery 2 inches from the upper end. Openings are provided on each end for the insertion of air line sections. The upper end receives the short air line section (16) while the lower end receives the air line section (31). The air line strap (32) is provided between the lower end of the soldered air line section (30) and the end of this inner tube section. It is secured over the air line section (31) after its assembly with two lockscrews (33). These lockscrews are inserted in clearance holes in the air line strap (32) and screwed into tapped holes in the inner tube section.

The upper part is a push fit and is soldered on the lower alignment support section of the sixth inner tube section upper end coupling (26) with eight lockscrews (28). These lockscrews are inserted in soldered countersunk clearance holes in the upper part of the sixth inner tube section and screwed into soldered tapped holes in the lower alignment support section in the sixth inner tube section upper end coupling (26) to form a permanent joint.

Two opposite tape straps (29) are soldered to the periphery of this inner tube section, located 3 3/4 inches from the lower end. These straps retain the shifting wire tapes (38, Figure 4-28) to the inner tube section and prevent them from binding and breaking as a result of looseness in the disassembly and reassembly of the inner tube in the outer tube (2, Figure 4-15).

The lower part of the inner tube section is a push fit and is soldered on the upper alignment

l. Sixth inner tube section upper end coupling. The sixth inner tube section upper end coupling (26) is made of cast phosphor bronze, and is 2.750 inches in length. It forms a joint between the lower part of the sixth inner tube section and the upper part of the fifth inner tube section. The upper part has a large bearing flange 3/4 inch in width, and its diameter is a few thousandths of an inch smaller than the inner diameter of the outer tube. This flange serves as a bearing to stabilize the upper part of the sixth inner tube section (23) in the outer tube, providing sufficient clearance for the prism tilt and power shifting wire tapes (38, Figure 4-28) and also the air line sections (16, 30, and 31). The lower shoulder of the bearing flange is chamfered at a 30 degrees angle.

In the lower part below the chamfered flange, a straight turned section-serves as an alignment support section and fits in the upper part of the sixth inner tube section (23). This alignment support section is turned a push fit into the upper part of the sixth inner tube section and soldered to it with eight lockscrews (28). Two air ports opposite each other are provided through the upper part of the sixth inner tube section 1 inch from the upper end. These ports are a small hole in the coupling, with a larger hole in the inner tube section. A wire screen is placed in the large hole, with a brass bushing soldered into this hole against the wire screen. The bushing is filled down to conform to the contour of the inner tube section periphery.

The internal diameter of the coupling is bored for light transmission. The upper part has an internal threaded section to receive the threaded periphery of the lower part of the reducing coupling (2), while the alignment support section below the threaded periphery is a sliding fit in the bore of the coupling. The reducing coupling (2) and the sixth inner tube section upper end

Four tape slots are provided in the bearing flange of the coupling, two opposite the others. A radial cross slot 4 inch from the upper end intersects the two outside shoulders of the two opposite tape slots for the insertion of two 0.040-inch bronze wires. These wires are soldered in place, and serve as, retainers for the prism tilt and change of power shifting wire tapes (38, Figure 4-28) to hold them in the slots. An air line slot is provided at right angles to the tape slots at assembly for the air line coupling (1S).

m. Sixth inner tube section lower end coupling. The sixth inner tube section lower end coupling (27) is made of phosphor bronze and is 4.125 inches in length. In the upper part it has a straight turned section which serves as an alignment support section for the lower part of the sixth inner tube section (23). This alignment support section is soldered and tinned a push fit in the lower part of the sixth inner tube section and secured with eight lockscrews (24). These lockscrews are inserted in soldered countersunk clearance holes in the lower part of the sixth inner tube section and screwed into soldered tapped holes in the upper alignment support section of the sixth inner tube section lower end coupling (27) to form a permanent joint.

The central part is provided with a large bearing flange 5/8 inch in width, and its diameter is a few thousandths of an inch smaller than the inner diameter of the outer tube. This flange serves as a bearing to stabilize the lower part of the sixth inner tube section (23) and the upper part of the fifth inner tube section (34) in the outer tube, providing sufficient clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28) as well as the air line sections (30 and 31). Four tape slots are provided in the bearing flange of the coupling, two opposite the others. A radial cross slot

The lower part of the coupling is provided with a threaded periphery and an alignment support section to receive the smooth bore and threaded part in the upper part of the fifth inner tube section. It is secured to the fifth inner tube section (34) with four lockscrews. These lockscrews are inserted in countersunk clearance holes in the upper part of the fifth inner tube section (34) and screwed into tapped holes in the lower alignment support section of the sixth inner tube section lower end coupling.

n. Fifth inner tube section. The fifth inner tube section (34) is made of cast phosphor bronze and is 10 inches in length. The inner and outer diameters are uniform throughout the entire length. The upper part has an internal threaded section 5/8 inch deep to screw on the threaded periphery of the lower part of the sixth inner tube section lower end coupling (27) which is secured with four lockscrews (35).

A 2-inch axial slot in the wall of this inner tube section located 2.625 inches from the lower end provides a means of axial movement for the upper objective lens mount (38). The axial focusing of this lens is necessary for primary and final collimation of the upper and lower telescope systems. The mount is secured, in this inner tube section with four lockscrews (36).

The lower part of this inner tube section has an internal threaded section 5/8 inch long to screw on the threaded periphery in the upper part of the fourth inner tube section upper end coupling (5). It is secured with four lockscrews (35).

A shallow vertical recess groove is provided at assembly the entire length of this inner tube section for the air line section (31). Four tape slots are provided in this inner tube section, two opposite the others for free movement of the prism tilt and change of power shifting wire tapes (38, Figure 4-28).

p. Upper objective lens mount. The upper objective lens mount (38) is made of cast phosphor bronze and is 5 inches in length. The external diameter of this mount is a sliding fit in the bore of the fifth inner tube section (34). Its internal diameter is bored for light transmission. The upper part has two counterbored sections. The smaller counterbored section accommodates the upper objective lens flint element (41) and crown element (42) separated by a spacer ring. The seat of the small counterbored section has two opposite air channels to provide sufficient clearance for the passage of nitrogen. The crown element (42) of the air-space doublet having the shortest radius rests against the seat in the mount. The upper objective lens clamp ring screws into the threaded section of the large counterbored section in the mount, and screws against the piano side of the flint element (41) which is secured with a lockscrew (37).

The lower part below the shoulder seat is counterbored and has anti-reflection threads. The lower part of the shoulder seat is chamfered to this counterbore at an angle of 8 degrees.

The mount is secured in the fifth inner tube section (34) with six lockscrews (36) after primary and final collimation. These lockscrews are inserted in countersunk clearance holes in the fifth inner tube section and screwed into tapped holes in the mount.

q. Upper objective lens spacer ring. The upper objective lens spacer ring (40) is made of aluminum tubing and is 0.062 inch wide. It is a sliding fit in the mount, and is placed between the concave surface of the flint element (41) and the longest radius surface of the crown element (42). The spacer ring is required between this doublet because lenses of large diameter cannot be cemented because of the difference in the thermal expansion coefficients of crown and flint glasses.

4I2. Part II: Upper telescope system. a. Description of the second, third, and fourth inner tube sections. These three inner tube sections have no lenses, but form the necessary inner tube bodies to enclose the inter-objective parallel light rays that are deflected downward to the magnifying lower telescope system. Figure 4-21 shows the upper telescope system assembly Part II. All bubble numbers in Sections 4I2, 5, and 6 refer to Figure 4-21 unless otherwise specified.

b. Fourth inner tube section. The fourth inner tube section (1) is made of brass tubing and is 90.292 inches long. The inner and outer diameters are uniform throughout the entire length. An air line section (10) 86 1/2 inches long is soldered to the periphery of this inner tube section 1 5/8 inches from the upper end. The air, line section is open at both ends to, receive the air line section (31, Figure 4-20) in the upper opening, while in the lower opening it receives the short unsoldered air line section (21).

Two tape straps (9) are soldered to opposite sides on the periphery to retain the prism tilt and change of power shifting wire tapes (38, Figure 4-28) to their required vertical centerline position.

The internal diameter of this inner tube section carries a diaphragm (7) which is located in

The upper part of the fourth inner tube section (1) is a push fit and is soldered on the alignment support section in the lower part of the fourth inner tube section upper end coupling (5) with eight lockscrews (2). These lockscrews are inserted into soldered countersunk clearance holes in the upper part of the fourth inner tube section (1) and screwed into soldered tapped holes in the lower alignment support section of the fourth inner tube section upper end coupling (5) to form a permanent joint.

The lower part of the fourth inner tube section (1) is a push fit and is soldered on the alignment support section in the upper part of the fourth inner tube section lower end coupling (6) with eight lockscrews (3). These lockscrews are inserted into soldered countersunk clearance holes in the lower part of the fourth inner tube section (1) and screwed into soldered tapped holes in the upper alignment support section of the fourth inner tube section lower end coupling (6).

c. Fourth inner tube section upper end coupling. The fourth inner tube section upper end coupling (5) is made of cast phosphor bronze and is 4.125 inches long. It forms a joint between the lower part of the fifth inner tube section and the upper part of the fourth inner tube section.

In the upper part, it is provided with a threaded periphery and-an alignment support section to receive the internal threaded section and smooth bore of the lower part of the fifth inner tube section which is secured with four lockscrews (35, Figure 4-20).

The central part is provided with a large bearing flange 5/8 inch wide, and its diameter is a few thousandths of an inch smaller than the inner diameter of the outer tube. This flange serves as a bearing to stabilize the upper part of the fourth inner tube section (1) and the lower part of the fifth inner tube section (34, Figure 4-20) in the outer tube, and to provide sufficient clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28) along with the air line sections (31 and 10, Figure 4-20). The inner diameter is bored for light transmission and has anti-reflection threads.

In the lower part it has a straight turned section which serves as an alignment support section to receive the upper part of the fourth inner tube section. This alignment support section is tinned a push fit in the upper part of the fourth inner tube section and is secured with eight lockscrews (2) and soldered. These lockscrews are inserted in soldered countersunk clearance holes in the upper part of the fourth inner tube section and screwed into tapped holes in the lower alignment support section of the fourth inner tube section upper end coupling (5) to form a permanent joint.

d. Diaphragm. The diaphragm (7) is made of 1/32-inch spun brass of light weight and is 2 inches in length. It is located in the central part of the fourth inner tube section. The side wall of the diaphragm has an opening sufficient to permit the necessary light transmission. The diaphragm restricts the light rays from striking the inner wall of the inner tube section and confines it to the necessary clear aperture required. Three equally spaced brass strips are soldered on the inner wall of the diaphragm. It is a push fit in the inner tube section and is secured with three lockscrews (8). These lockscrews are inserted in countersunk clearance holes in the fourth inner tube section and screwed into tapped holes in the soldered strips in the diaphragm.

e. Fourth inner tube section lower end coupling. The fourth inner tube section lower end coupling (6) is made of cast phosphor bronze 4.125 inches in length. It forms a joint between the lower part of the fourth inner tube section (1) and the third inner tube section upper end coupling (17).

In the upper part it has a straight turned section which serves as an alignment support

Near the central part it is provided with a large bearing flange 5 inch in width, and its diameter is a few thousandths of an inch smaller than the inner diameter of the outer tube. This flange serves as a bearing to stabilize the lower part of the fourth inner tube section (1) in the outer tube, providing sufficient clearance for the prism tilt and change of power shifting wire tapes (38), the air line section (10), and the short air line section (21).

Four tape slots are provided in the bearing flange of the coupling, two opposite the others. Two radial cross slots located in the center intersect the two outside shoulders of each opposite set of tape slots, for the insertion of two 0.040-inch bronze wires. These wires are soldered in place, and serve as retainers for the prim tilt and change of power shifting wire tapes (38, Figure 4-28) to hold them in the slots. An air line slot is provided at right angles to the tape slots at assembly for the air line section (21). The inner diameter is bored for light transmission and has anti-reflection threads.

In the lower part below the large bearing flange it has a straight turned section which is larger in diameter than the alignment support section located in the upper part of the bearing flange. This section is counterbored and is threaded a depth of 5/8 inch. It serves as an alignment support section to receive the alignment support section in the upper part of the third inner tube section upper end coupling (17) and provides a removable joint between these couplings. It receives the threaded periphery of the third inner tube section upper end coupling (17) and is secured with four lockscrews (4). These lockscrews are inserted into countersunk clearance holes in the lower part of the fourth inner tube section lower end coupling

f. Third inner tube section. The third inner tube section (11) is made of brass tubing and is 90.292 inches in length. The inner and outer diameters are uniform throughout its length. An air line section (20), 86 1/2 inches long, is soldered to the periphery of this inner tube section two inches from the upper end. This air line section is open on both ends to receive air line sections over the joints. The short air line section (21) fits into the upper opening, while the air line section (29) fits into the lower opening. Two tape straps (19) are soldered to opposite sides on the periphery of this inner tube section near the lower part, to retain the prism tilt and change of power shifting wire tapes (38, Figure 4-28) to their required vertical centerline position.

The upper part is a push fit and is soldered on the alignment support section in the lower part of the third inner tube section upper end coupling (17) with eight lockscrews (13). These lockscrews are inserted in soldered countersunk clearance holes in the upper part of the third inner tube section (11) and screwed into the soldered tapped holes in the lower alignment support section of the third inner tube section upper end coupling (17) to form a permanent joint.

The lower part of the inner tube section is a push fit and is soldered on the upper alignment support section of the third inner tube section lower end coupling (16).

g. Third inner tube section upper end coupling. The third inner tube section upper end coupling (17) is made of cast phosphor bronze and is 4.125 inches in length. It forms a joint between the fourth inner tube section lower end coupling (6) and the upper part of the third inner tube section (11).

It is similar to the fourth inner tube section upper end coupling (5) and is soldered to the upper part of the third inner tube section (11) with eight soldered lockscrews (13) to form a permanent joint.

The upper alignment support section is a sliding fit into the counterbore of the fourth

A diaphragm (18) is secured in the lower part of this coupling with the side wall facing downward, and is secured with three lockscrews (15).

h. Diaphragms. The two diaphragms (18) are similar to the diaphragm (7) of the fourth inner tube section (1) except for the outside diameter. One is secured in the bore in the lower part of the third inner tube section upper end coupling (17) with its side wall facing downward. It is secured with three lockscrews (15), which are inserted in countersunk clearance holes in the upper part of the third inner tube section (11) through clearance holes in the lower alignment support section of the third inner tube section upper end coupling (17) and screwed into tapped holes in the-diaphragm (18).

The second diaphragm (18) is secured in the bore in the upper part of the third inner tube section lower end coupling (16) with the side wall facing upward. It is secured with three lockscrews (15) which are inserted into countersunk clearance holes in the lower part of the third inner tube section (11) through clearance holes in the upper alignment support section of the third inner tube section lower end coupling (16) and screwed into tapped holes in the diaphragm (18).

i. Third inner tube section lower end coupling. The third inner tube section lower end coupling (16) is identical to the fourth inner tube section lower end coupling (6). It forms a joint between the lower part of the third inner tube section (11) and the second inner tube section upper end coupling (25).

The alignment support section in the upper part is tinned a push fit and soldered in the lower part of the third inner tube section (11) with eight lockscrews (14) to form a permanent joint. The bore of this upper part carries the diaphragm (18) with the side wall of the diaphragm facing upward.

The bore and threaded section in the lower part of this coupling receives the upper alignment support section and threaded periphery of the second inner tube section upper end coupling (25) as a removable joint between these couplings.

Four air line straps are spaced equally over the air line section (29) of the second inner tube section. Three of these air line straps (31) are soldered to the periphery while the removable air line strap (30) is secured with two lockscrews (32). These lockscrews are inserted into clearance holes in the air line strap (30) and screwed into tapped holes in the periphery wall.

Two tape straps (27) are soldered to opposite sides on the periphery of the lower part, to retain the prism tilt and change of power shifting wire tapes (38, Figure 4-28) to their required vertical centerline position.

The upper part of this inner tube section is a push fit and is soldered on the lower alignment support section of the second inner tube section upper end coupling (25) with eight lockscrews (23). These lockscrews are inserted in soldered countersunk clearance holes in the upper part of the second inner tube section and screwed into soldered tapped holes in the lower alignment support section of the second inner tube section upper end coupling (25) to form a permanent joint.

The lower part of the second inner tube section (22) is a push fit on the tinned upper alignment support section of the second inner tube section lower end coupling (26). It is soldered at assembly with eight lockscrews (24). These lockscrews are inserted in soldered countersunk clearance holes in the lower part of the second inner tube section and screwed into soldered tapped holes in the upper alignment support of the second inner tube section lower end coupling (26) to form a permanent joint.

k. Second inner tube section upper end coupling. The second inner tube section upper end coupling (25) is identical to the third inner tube section upper end coupling (17) and similar to the fourth inner tube section upper end

It is soldered to the upper part of the second inner tube section (22) with eight soldered lockscrews (23) to form a permanent joint.

The upper alignment support section is a sliding fit into the counterbored section in the third inner tube section lower end coupling (16), while the threaded periphery screws into the threaded section of the same counterbored section.

1. Second inner tube section lower end coupling. The second inner tube section lower end coupling (26) is made of cast phosphor bronze and is 3.687 inches in length. It forms a joint between the lower part of the second inner tube section (22) and the upper part of the lower (split) objective lens coupling sleeve (34, Figure 4-23) of the lower telescope system.

In the upper part it has a straight turned section which serves as an alignment support section for the lower part of the second inner tube section (22). This alignment support section is tinned a push fit into the lower part of the second inner tube section and is soldered at assembly and secured with eight lockscrews (24). These lockscrews are inserted in soldered countersunk clearance holes in the lower part of the second inner tube section and screwed into soldered tapped holes in the upper alignment support section of the second inner tube section lower end coupling (26) to form a permanent joint.

Near the central part it is provided with a large bearing flange 3/8 inch in width, and its diameter is a few thousandths of an inch smaller than the inner counterbore of the lower part of the outer tube. This flange serves as a bearing to stabilize the lower part of the second inner tube section (22) in the counterbore of the outer tube, providing sufficient clearance for the prism tilt and change of power shifting wire tapes (38, Figure 4-28) as well as the air line section (29).

Four tape slots are provided in the bearing flange of the coupling, two opposite the others. An air line slot is provided at right angles to

In the lower part below the bearing flange, it has a straight turned section which is larger in diameter than the alignment support section in the upper part of the bearing flange, and is provided with a threaded periphery section. This alignment support section is a sliding fit in the bore in the upper part of the lower (split) objective lens coupling sleeve (34, Figure 4-23) while the threaded periphery screws into the internal threaded section in the upper part of this coupling sleeve. It is secured with four lockscrews (22, Figure 4-23) which are inserted in countersunk clearance holes in the coupling sleeve and screwed into tapped holes in the lower alignment support section of this coupling. The inner diameter is bored for light transmission and provided with anti-reflection threads.

The lower part is counterbored a depth of 1 7/16 inches and provided with anti-reflection threads.

4I3. Disassembly of Part I. The first reduced tube section and the fifth and sixth inner tube sections are disassembled in the following manner:

1. Separate the lower part of the first reduced tube section (1) from the upper part of the reducing coupling (2) as follows:

2. Remove the four lockscrews (12) from the reducing coupling (2). These lockscrews are unscrewed from tapped holes in the first reduced tube section (1).

3. Unscrew the first reduced tube section (1) from the upper part of the reducing coupling (2).

4. Remove the lockscrew (7) from the diaphragm (13), unscrewing it from the tapped hole in the diaphragm (13).

5. Remove the diaphragm (13) by unscrewing it.

6. Remove the lockscrew (7) from the collective lens mount (3). This lockscrew is unscrewed from the tapped hole in the mount.

7. Unscrew the collective lens mount (3) and remove the assembled mount with the collective lens (21) and the clamp ring (4).

9. Using a special wrench, unscrew the clamp ring (4). Remove the clamp ring from the mount (3).

10. Turn the collective lens mount (3) on a piece of lens tissue, placing it on its lower face. Using a piece of lens tissue on the opposite side, press downward on the lens tissue and the collective lens (21) for its removal.

11. Remove the two lockscrews (10) from the upper eyepiece lens mount (6). These lockscrews are unscrewed from tapped holes in the mount, and are carried out of countersunk clearance holes in the first reduced tube section (1).

12. Using a special pair of calipers inserted in opposite holes in the upper part of the upper eyepiece lens mount (6), slide the upper eyepiece lens mount (6) out from the upper part of the first reduced tube section (1), removing the mount, upper eyepiece lens (20), and clamp ring (5).

13. Remove the lockscrew (9) from the upper eyepiece lens mount (6) and clamp ring (5). This lockscrew is unscrewed from the tapped hole in the mount and the clamp ring.

14. Using a special wrench, unscrew the upper eyepiece lens clamp ring (5) and remove it from the mount (6).

15. Place the upper eyepiece lens mount (6) on a piece of lens tissue, turning it on its upper face. Using a piece of lens tissue on the opposite side, press downward on the lens tissue and the upper eyepiece lens (20) for its removal. Wrap the lens doublet in clean lens tissue and store it in a box to prevent scratches and breakage.

16. Separate the lower part of the reducing coupling (2) from the upper part of the sixth inner tube section upper end coupling (26) as follows:

17. Remove the four lockscrews (25) from the upper part of the sixth inner tube section (23). These lockscrews are unscrewed from tapped holes in the lower alignment support section of the reducing coupling (2).

19. Separate the fifth inner tube section (34) from the sixth inner tube section lower end coupling (27) as follows:

20. Remove the four lockscrews (35) from the upper part of the fifth inner tube section (34). These lockscrews are unscrewed from tapped holes in the lower alignment support section of the sixth inner tube section lower end coupling (27).

21. Remove the fifth inner tube section (34) from the lower part of the sixth inner tube section lower end coupling (27) by unscrewing the fifth inner tube section.

22. Remove the six lockscrews (36), unscrewing them from the tapped holes in the upper objective lens mount (38).

23. Remove the upper objective lens mount (38) from the fifth inner tube section (34). The mount can be slid out from either end. Remove the assembled mount (38) with the upper objective lens (41 and 42), upper objective lens spacer ring (40), and the upper objective lens clamp ring (39).

24. Remove the lockscrew (37) from the upper objective lens mount (38). This lockscrew is unscrewed from the tapped hole in the clamp ring (39).

25. Using a special wrench, unscrew the upper objective lens clamp ring (39) from the upper part of the lens mount (38).

26. Place the upper objective lens mount (38) over a special padded block. The mount slides down over the block, with the upper objective lens elements (41 and 42) and the, upper objective lens spacer ring (40) remaining on the padded part of the block.

27. Wrap the flint and crown elements of the upper objective lens doublet (41 and 42) with lens tissue and store them in a box to prevent scratches and breakage.

414. Reassembly of Part I. The reassembly of the first reduced tube section and the fifth and sixth inner tube sections is effected in the following manner:

2. Clean the upper eyepiece lens (20) with clean lens tissue. Surface dust can be removed with a rubber air bulb and a clean camel's hair brush or a vacuum brush used with ether.

3. Place the upper eyepiece lens (20) in the upper eyepiece lens mount (6). The convex face of this doublet is placed toward the seat of the mount.

4. Place the upper eyepiece lens clamp ring (5) in the threaded section in the upper part of the mount (6). Screw this clamp ring tight against the plano face of the upper eyepiece lens doublet. The lockscrew holes should coincide when the lens is tightened sufficiently.

5. Insert and secure the lockscrew (9), screwing it into the tapped hole in the mount (6) and the partially tapped hole in the clamp ring (5).

6. Slide the assembled upper eyepiece lens mount (6) into the upper part of the first reduced tube section (1). The clamp ring side of the assembled mount should be located upward.

7. The lockscrews (10) should not be inserted in the countersunk clearance holes in the first inner tube section (1) and the tapped holes in the mount (6) until completion of the primary and final collimation of both the upper and lower telescope systems. One lockscrew (10) should be inserted temporarily until ready for collimation. Place the remaining lockscrews in a small box until ready for the securement of the mount.

8. Clean the collective lens (21) in similar manner to that outlined in Step 2.

9. Place the collective lens (21) in the collective lens mount (3). The plano face of the lens is placed toward the shoulder seat of the mount.

10. Place the collective lens clamp ring (4) in the threaded counterbore of the upper part of the mount. The lockscrew holes coincide when

11. Insert and secure the lockscrew (11), screwing it into the tapped hole of the mount (3) and the partially tapped hole of the clamp ring (21).

12. Place the assembled collective lens mount (3) in the threaded counterbore in the lower part of the first reduced tube section (1). The mount is placed with the clamp ring side facing downward. Screw the mount into this reduced tube section until the tapped hole in the mount coincides with the clearance hole in the reduced tube section.

13. Insert and secure the lockscrew (7), screwing it into the tapped hole in the mount (3).

14. During the primary collimation of the upper telescope system with the lower telescope system, it is necessary to install a temporary mechanical crossline adapter with attached crosswires (Figure 4-56). This requires that the replacement of the diaphragm (13) and its lockscrew (7) be deferred until after primary collimation.

15. The lower part of the temporary crossline adapter is angularly adjusted so that the repairman can square its crossline section for a temporary orientation. A lockscrew, inserted through the circumferential slot of the squaring mount into the tapped hole in the body of the adapter, enables the repairman to secure the crosswires at a fixed position.

16. The purpose of the mechanical crosswise is to establish a target on which the upper objective lens is focused, and also to provide a reference point from which the correct position of the collective lens is found. Refer to Section 4V4.

17. Place the diaphragm (13) and its lockscrew (7) to one side until after primary collimation.

18. Connect the lower part of the first reduced tube section (1) to the upper part of the reducing coupling (2) as follows:

19. Screw the lower part of the first reduced tube section (1) into the threaded section of the upper part of the reducing coupling (2).

21. Connect the lower part of the reducing coupling (2) in the upper part of the sixth inner tube section upper end coupling (26) as follows:

22. Screw the lower part of the reducing coupling (2) into the internal threaded section in the upper part of the sixth inner tube section upper end coupling (26).

23. Insert and secure the four lockscrews (25), inserting them in countersunk clearance holes in the upper part of the sixth inner tube section, thence through clearance holes in the sixth inner tube section upper end coupling alignment support section and screwing them into the tapped holes in the lower alignment support section of the reducing coupling (2).

24. Clean the upper objective lens flint element (41) and crown element (42) in similar manner to the procedure described under Step 2.

25. Place the plano side of the flint element (41) on the special padded surface wooden block. Place the upper objective lens spacer ring (40) on the concave surface of the flint element lace the longest radius of the double convex crown-element (42) on the spacer ring. Line up the periphery of both elements and the spacer ring.

26. Place the upper objective lens mount (38) with the clamp ring side facing downward over the assembled upper objective lens doublet and the padded wooden block. Turn the complete assembly with the padded block over so that the crown element (42) with the shortest radius is resting in the shoulder seat of the mount,

27. Place the clamp ring (39) in the internal threaded section in the upper part of the upper objective lens mount (38). Using a special wrench, screw this clamp ring tightly against the plano side of the flint element (41). The lockscrew holes should coincide when the lens is tightened sufficiently.

29. Slide the upper objective lens mount (38) into the fifth inner tube section (34). The clamp ring side of the assembled mount should face upward.

30. The upper objective lens mount (38) is not secured until completion of primary and final collimation.

31. Insert and secure one of the six lockscrews (36) in the tapped hole in the mount; until ready for collimation. Place the remaining five lockscrews in a small box until ready for the securement of the mount.

32. Connect the fifth inner tube section to the lower part of the sixth inner tube section lower end coupling (27) as follows:

33. Screw the upper part of the fifth inner tube section (34) on the lower alignment support section and threaded periphery of the sixth inner tube section lower end coupling (27).

34. Insert and secure the four lockscrews (35) inserting them in countersunk clearance holes in the upper part of the fifth inner tube section (34) and screwing them into the tapped holes in the lower alignment section of the sixth inner tube section lower end coupling (27).

4I5. Disassembly of Part II. The second, third, and fourth inner tube sections are disassembled in the following manner:

1. Separate the fourth inner tube section lower end coupling (6) from the third inner tube section upper end coupling (17) as follows:

2. Remove the four lockscrews (4) from the fourth inner tube section lower end coupling (6). These lockscrews are unscrewed from the tapped holes in the upper alignment support section of the third inner tube section upper end coupling (17).

3. Unscrew the lower part of the fourth inner tube section lower end coupling (6) from the upper part of the third inner tube section upper end coupling (17). This removes the fourth inner tube section and its lower end coupling

4. Separate the third inner tube section lower end coupling (16) from the second inner tube section upper end coupling (25) as follows:

5. Remove the four lockscrews (12) from the third inner tube section lower end coupling (16). These lockscrews are unscrewed from the tapped holes in the upper alignment support section of the second inner tube section upper end coupling (25).

6. Unscrew the upper part of the second inner tube section upper end coupling (25) from the lower part of the third inner tube section lower end coupling (16). This removes the second inner tube section and its upper end coupling from its connection with the third inner tube section and its lower end coupling.

7. If it is necessary to remove the two diaphragms (18) from the third inner tube section upper and lower end couplings (17 and 16), remove the three lockscrews (15) each from the upper and lower parts of the third inner tube section (11). These lockscrews are unscrewed from tapped holes in each diaphragm (18). The diaphragms can pulled out easily, as they are a push fit into these two couplings.

4I6. Reassembly of Part II. The second, third, and fourth inner tube sections are reassembled in the following manner:

1. Using an air hose, blow out the internal surfaces of the second inner tube section. If a circular brush is available, it should be used first.

2. Place the two diaphragms (18) in the third inner tube section upper and lower end couplings (17 and 16). The side wall of each diaphragm should face inward toward the inner part of this inner tube section.

3. Insert and secure the three lockscrews (15) in each diaphragm (18). These lockscrews are inserted in countersunk clearance holes in the inner tube section thence through clearance holes in their respective coupling and screwed into tapped holes in each diaphragm.

4. Screw the upper part of the second inner tube section upper end coupling (25) into the internal threaded section of the third inner tube section lower end coupling (16).

5. Secure the third inner tube section lower end coupling (16) to the second inner tube section upper end coupling (25) with four lockscrews (12). These lockscrews are inserted in countersunk clearance holes in the third inner tube section lower end coupling and screwed into tapped holes in the upper alignment support section of the second inner tube section upper end coupling (25).

6. Screw the upper part of the third inner tube section upper end coupling (17) into the internal threaded section in the lower part of the fourth inner tube section lower end coupling (6).

7. Secure the fourth inner tube section lower end coupling (6) to the third inner tube section upper end coupling (17) with four lockscrews (4). These lockscrews are inserted into countersunk clearance holes in the fourth inner tube section lower end coupling and screwed into tapped holes in the upper alignment support section of the third inner tube section upper end coupling (17).