[Panoramic Telescope M8]
[From the U.S. Government Publishing Office, www.gpo.gov]

Document ----------------------
Reserve	WAR DEPARTMENT
TECHNICAL MANUAL
ORDNANCE MAINTENANCE
PANORAMIC TELESCOPE M8
August 15,1942
NON-CIRCULATING

VJ|,35:	9-1582
*TM 9-1582
1
TECHNICAL MANUAL No. 9-1582
WAR DEPARTMENT, Washington, August 15, 1942.
ORDNANCE MAINTENANCE
PANORAMIC TELESCOPE M8
Section I. General.	Paragraph
Scope_____ __________________________________ 1
II.	Description.
General_________________________________________ 2
Optical system______________________________     3
Mechanical construction________________________  4
Illumination____________________________________ 5
III.	Operation.
General_________________________________________ 6
Leveling ami adjusting___________________________7
Pointing in direction_____________-__________ 8
IV.	Inspection.
Procedure_____________________ _ _ i______„	9
V.	Maintenance and repair.
Tools________________________________________   10
Disassembly and assembly_______________________ 11
Adjustment_____________________________________ 12
VI.	Care and preservation.
Care in handling_______________________________ 13
Optical parts__________________________________ 14
Lubrication___________________________________  15
VII.	Accessories.
Packing chest__________________________________ 16
Electrical equipment___________________________ 17
Page
Appendix.	List of references_ ----------------------------    27
Section I
GENERAL
Paragraph
Scope________________________________________________________ 1
1.	Scope.—a. This manual supplements the Technical Manuals on the panoramic telescope prepared for the using arm. It contains general descriptive matter and detailed instructions for the maintenance and repair of the instrument by ordnance personnel. Figures
*This manual together with TM 9-1554, July 24, 1942, supersedes TM 9—2554, August 20, 1941.
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1 to 12, inclusive, show the position and construction of each component part of the instrument.
b. The panoramic telescope M8 is the sighting element of the fire-control system used for laying in direction the 155-mm gun on the
Figure I.—Panoramic telescope MS.
155-mm gun carriage M3, and is mounted in telescope mount M6A1. It is also used for laying in direction the 8-inch railway gun on the 8-incli railway mount Ml Al, and is mounted on this carriage in tele-

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PANORAMIC TELESCOPE M8
scope mount M20. The telescope is designed for use in case IT and case III pointing, and is fastened in the telescope mount on the respective gun mount.
Section II
DESCRIPTION
Paragraph
General_____________________________________________________________________ 2
Optical system______________________________________________________________ 3
Mechanical construction_____________________________________________________ 4
Illumination________________________________________________________________ 5
2.	General.—Panoramic telescope M8 has a movable head graduated for 360° azimuth rotation. Adjustment in elevation is provided to bring the cross lines to bear on a target. The erecting prisms, which take the place of the dove reflecting prism usually used in panoramic telescopes are in the lower horizontal leg of the telescope. Two large micrometer knobs and the 90° elbow are distinguishing characteristics of this instrument.
3.	Optical system.—a. This optical system includes window (A48091) ; 90° rotating prism (A46089) ; objective (A48092) ; Amici prism (B173197) ; erecting prism assembly consisting of two prisms (A45499 and A45500) ; reticle (A48093) ; field lens (A48095) ; eye lens (A48096) ; and amber filter (A179217), or neutral filter (Al79218). (See fig. 8.)
b. The optical characteristics are as follows:
Power_________________________________________6X
Field of	view_______________________________ 6°40'
Diameter	of exit	pupil______________________.20 inch
Effective focal length of objective___________7.58 inches
Effective focal length of eyepiece____________ 1.263 inches
Apparent	field	of view______________________4°
4.	Mechanical construction.—a. General— Panoramic telescope M8 consists primarily of the rotating head assembly, the azimuth mechanism, and the elbow telescope assembly. A lighting system provides necessary illumination (fig. 1).
b. Rotating head assembly.— (1) The 90° rotating head prism (A46089) and prism holder (C69671) rotate in a vertical plane within the rotating head assembly (D28722) when the knob (A48097) is operated (figs. 5 and 8). The elevating worm knob stop rings (A49929 and A49930) limit the range of elevation or depression
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(fig. 3). When both sets of indexes are alined (fig. 2) the rotating-head assembly is in normal position.
(2)	The window (A48091) mounted in front of the 90° rotating head prism seals the upper end of the telescope against dust and moisture.
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Figure 2.—Panoramic telescope M8—assembled views.
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PANORAMIC TELESCOPE M8
(3) The open sight (fig. 2) used for rough sighting, is parallel to the line of sight through the telescope when the 90° rotating head prism is in the normal position.
c. Azimuth mechanism.— (1) Two micrometer knobs (fig. 6) are provided to direct the panoramic telescope M8. The left knob (B138643) is used for case III pointing, and the right knob (B138644) for case II pointing (fig. 6). Both micrometers are graduated at
MICROMETER CLAMPING SCREWS^
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Figukhi 3.—Elevating micrometer, schematic diagram.
intervals of 0.05° and numbered at intervals of 0.5°. A complete revolution of the micrometer represents 10°.
(«) The left micrometer (fig. 1), used for case III pointing is numbered from 0-9 with 0 as normal. The right micrometer used in case II pointing for setting corrections by reference numbers is numbered from 5-14 with 10 as normal.
(&)	The correction scale etched on worm shoe (B138705) is graduated at .05° intervals and permits 1° correction on each side of normal (figs. 2 and 6).
(2)	The azimuth scale (B138703, figs. 2 and 8) is graduated and numbered at 10° intervals from 0° to 350°, clockwise. It is clamped
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to the lower shank of the rotating head by an adjustable azimuth index assembly (B138762).
(3)	The ratchet (B138704) of the azimuth index assembly (B138-753) and the detent (A179197) riveted to the worm shoe (B138705) cause the adjustable micrometer index to stop in coincidence with a graduation on the correction scale. The ratchet also prevents slipping of the index with respect to the correction scale (fig. 4).
(4)	rhe knobs (B138643 and B138644, fig. 6) operate a train of bevel gears which turn the rotating head assembly (D28722, fig. 8) and rotate the erecting prism assembly (B136669), keeping the image erect at all times.
CLAMPING ADAPTER	INDEX LEVER
clamp.	/y	J
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IF ill
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KNOB	L MICROMETER / '-INDEX	RA PD 7107
RATCHET
Fioukk 4. Azimuth micrometer, schematic diagram.
(a) The bevel gear (B138655) which is press-fitted to the worm gear (C70153) meshes with bevel pinion (B138656).
(Z>) The bevel pinion (B138656) rotating on a stud which is integral with the miter gear (C56884) turns the miter gear through one-half the angle traveled by the bevel gear (B138655). The bevel pinion (B138656) also meshes with the bevel gear (B138654).
(c) The bevel gear (B138654) is press-fitted to the support (D29-291) and does not rotate.
( |	shown out of position 90
--PLUG-A48595	-------------CAP -AI79I89
INDEX, ASSEMBLY-B138753 -
SOCKET-AI79I90--; I ----------------WASHER-A 179187
MICROMETER - B138647-i
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SHOWN OUT OF POSITION 90
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RING - A4864I-------------
RA PD 7142
SCREW-BCGX3CC--------------1
SHOWN OUT OF POSITION 90*
Figure 6.—Panoramic telescope, M8-—section B—B.
the rotating head, contains the erecting prisms located in the prism support (C79326). Adjusting screws center this support on the spherical surface of miter gear (C70151). The spring washer (A185299) presses the prism against this surface and maintains the alinement. Access holes for the adjusting screws are sealed by screws (A185498).
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PANORAMIC TELESCOPE M8	4-7
(4)	The eyepiece adapter (C70152) is secured to the telescope elbow and contains the reticle (B138756) and window (A178192) through which the reticle is illuminated. The adapter is threaded at the end to receive the eyepiece assembly (C56978), composed of eyelens, cell, sleeve, field lens, and retaining ring.
(5)	The reticle (B138756, figs. 7 and 8) has a pattern consisting of a vertical and horizontal cross line.
(6)	The eyepiece assembly (C56978), besides field lens (A48095) and eyelens (A48096), contains the diopter scale (B137176), graduated from +3 to —3 diopters. The setting for normal vision is zero.
(7)	Two filter assemblies (B138670, amber, and B138671, neutral) are provided to shield the observer’s eye from those light rays which would prevent a clear image because of certain light wave intensities producing a blurring effect.
(8)	A soft rubber bellows-shaped eyeshield (B138699) cuts off stray light and protects the observer’s eye from harmful light rays.
5.	Illumination.—The telescope has two lamps for illumination of the reticle and one for the micrometers and scales. The reticle illuminating window cover assembly (B138701. fig. 7) protects the reticle window (A178192) and affords adjustment of the illumination. (See par. 17.)
Section III
OPERATION
Paragraph
General---------------------------------------------------------------------- 6
Leveling and adjusting------------------------------------------------------- 7
Pointing in direction-------------------------------------------------------- 8
6.	General.—The panoramic telescope M8 is used with telescope mount M6A1 and telescope mount M20. These mounts have different operating characteristics. Detailed operating instructions for the panoramic telescope M8 with each telescope mount are included in Technical Manuals pertaining to the particular telescope mount. Operating instructions applying to the panoramic telescope M8 only are included in this manual.
7.	Leveling and adjusting.—The telescope mount must be kept properly cross-leveled at all times and leveled longitudinally, when required, to insure that true horizontal and vertical angles will be measured and that proper azimuth corrections will be automatically applied. Both the mount and the telescope must be in adjustment before operation. (See par. 12.)
474398°—42—2
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PANORAMIC TELESCOPE M8	8-9
8.	Pointing in direction.—a. Applying lateral correction to individual gun.—To set off a constant small correction of 1° or less, rotate case III azimuth index (D138653) in direction until the correction is indicated on the correction scale. Set the zero of the azimuth micrometer (D138G47) opposite this index. This establishes the initial or zero correction. Subsequent deflections in azimuth may be set in either direction by rotating the azimuth setting or deflection setting knobs.
b. Setting defections for case II pointing.-—Deflections of 5° or less can be set by rotating the knob of the deflection micrometer (B138646) until the deflection is indicated opposite the case II index.
c. Setting azimuths for case 111 pointing.—Set off the announced azimuth of the set-forward point to the nearest 10° on the azimuth scale (B138703) and to the exact fraction of degree on the azimuth micrometer (B138647) of the panoramic telescope (fig. G). The vertical line of the telescope is brought to bear on the aiming point by operating the traversing handwheel of the gun carriage.
Section IV
INSPECTION
Paragraph
Procedure_______________________________________________ 9
9. Procedure.—Inspections are made to determine the condition of the panoramic telescope, whether repairs or adjustments are required. and the remedies necessary to insure serviceability and proper functioning.
Parts to be inspected
Points to be observed
a.	Exposed mechanical parts.
b.	Optical system.
a.	Observe general appearance. Note any bent or missing parts. Locating surfaces must be free of nicks and burs. Graduations should be clearly legible.
b.	Note if checks or frost marks appear in the field of view. Such defects are evidence of loosening of the balsam used in cementing lenses and, if severe, require the return of the telescope to an arsenal or base shop. Note presence of objectionable scratches on lenses. Windows should be clean.
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Parts to be inspected
c. Open sight.
d. Erecting prisms.
e. Elevating indexes.
/. Reticle.
g. Eyepiece assembly.
h. Objective.
Points to be observed
c.	The line of sight should be parallel to the optical line of sight within 0.5° (8.9 mils) in the horizontal and vertical planes. A testing target graduated in degrees or mils may be used.
d.	With the telescope clamped on a stable leveled surface, operate the azimuth knobs to rotate the head while viewing a fairly distant object. Observe whether the target remains erect as the head is rotated. If the target appears to depart from an erect position, the erecting prisms or mechanism require adjustment. For this test, the azimuth testing fixture (fig. 9) may be used.
e.	When the optical line of sight is horizontal and parallel to the azimuth locating surfaces of the telescope, the fixed and movable indexes of the elevation micrometer and coarse elevation index should exactly match.
f.	Test for vertical and horizontal positioning of the reticle cross lines by sighting on a vertical line, such as a plumb line, with the telescope level. Test for aline-ment with optical axis.
g.	While sighting on the cross lines of the collimating telescope, focus the eyepiece for sharpness and clarity of definition. The reading at optimum focus should be zero. The rubber eyeshield should be clean and in good condition.
h.	The objective should be in adjustment so that there is no parallax between the image and the lines at the center of the reticle when a suitable target is viewed at a distance of 275 yards ± 40 yards.
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PANORAMIC TELESCOPE M8
Parts to be inspected
Points to be observed
i.	Azimuth mechanism.
j.	Azimuth throw-out.
k.	Azimuth adjustable index.
1.	Reticle window cover.
m.	Lamps.
i.	Operate micrometers throughout the entire range, checking for binding or excessive play. Backlash due to excessive play should not exceed 0.05°. Azimuth scale graduations should aline exactly with the index when the zero of the azimuth micrometer alines with the micrometer index.
j.	Check the throw-out mechanism to make sure the azimuth worm and worm gear may be disengaged at any point.
k.	The azimuth adjustable index should clamp the azimuth scale when the thumbscrew is tightened and should allow the scale to rotate when the thumbscrew is unclamped. The detent and ratchet should aline with each graduation on the correction scale within 0.01° (l/5 of the space between graduations).
Z. Turn the reticle window cover. There should be no binding or play.
m. Try the lamp brackets in their clips for looseness or jamming. Lamps and sockets should be in good condition.
Section V
MAINTENANCE AND REPAIR
Paragraph
Tools_________________________________________________________________ 10
Disassembly and	assembly_____________________________________________ 11
Adjustment____________________________________________________________ 12
10. Tools.—a. Instrument repair kit.—An optical repair kit containing necessary tools, cements, oils, etc., for use with this instrument is furnished ordnance maintenance personnel. Most of the items, such as screw drivers, require no description as their uses are self-explanatory. An ordinary nonerecting collimating telescope is furnished with the kit.
Z>. Other tools.— (1) No tools are supplied with the panoramic telescope M8 but it is recommended that a pair of strap wrenches be used for unscrewing the large-diameter threaded sections. The strap
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10-11	ORDNANCE MAINTENANCE
wrenches should be not more than 8 to 12 inches long to avoid use of excessive force. Caution is recommended to avoid stripping threads or denting surfaces.
(2) The azimuth testing fixture (fig. 9), fitted with an adapter to accommodate the panoramic telescope, may be used where available. (An illustration of the azimuth testing fixture adapter is not included in this manual.)
(3) Other items of equipment used in inspection and readily available to the ordnance maintenance company are: a sensitive spirit level; a V-block for holding the collimating telescope; a sturdy workbench, affording a long space in front of the telescope to carry out optical tests; and a suitable testing target.
11. Disassembly and assembly.—Disassembly of the instrument may be required for cleaning or repair. Disassembly and assembly of the panoramic telescope M8 should be performed in a warm, dry, dust-free room whenever possible. For repairs that cannot be made with the facilities available, the instrument will be turned in to the base shop or arsenal. Assembly may be made by reversing steps taken in disassembly except where indicated. Before disassembling parts of the panoramic telescope M8, carefully mark their location with respect to each other to aid in realinement. Take note of any original markings. Reference to illustrations will indicate relationship of parts. Careful study of the illustrations should be made before attempting any-disassembly or assembly.
a.	Rotating head assembly^—To disassemble the rotating head assembly from the telescope, remove the two-piece clamping ring (B137159)( secured by four screws. Remove the three screws (BCLX3CD) which fasten the rotating head assembly to the worm gear (C70153). Unscrew the rotating head from the gear hub. The azimuth scale (B138703) and the adjustable index assembly (B138762) are removed at this point.
(1)	^Window.—To remove window (A48091, fig. 8) remove window frame (B138702) and the six securing screws (A49945D). Push the window out of its seat in the frame. Before reassembly, seal the rim of the window with compound, sealing (black, Navy).
(2)	Elevation worm mechanism.—To disassemble the elevation worm mechanism (fig. 8) —
(«) Withdraw plug (A34654) and locking screw spring (A33526) and plunger (A48657). Remove elevation worm knob (A48097) secured by three screws (BCGX3CC).
(6)	Drive out taper pin (BFCX1A) and remove the nine stop rings (A49929) and the stop ring (A49930).
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PANORAMIC TELESCOPE M8	11
(c)	Unscrew ball cap (A32115) and pull out worm (A179206) and socket (A32120), turning the worm if required to clear the prism holder teeth.
(<7) In reassembly, make sure that all perceptible play and backlash have been eliminated. Before reassembly, coat the worm lightly with grease (see par. 15). After reassembly, the stop ring mechanism should permit rotation through eight or nine revolutions of the micrometer, half above and half below the micrometer index.
(3)	Prism holder assembly.— (a) To withdraw prism holder assembly (C56977, figs. 7 and 8) after the elevation worm has been withdrawn, remove disk (A48142) and index ring (A179216) with the four retaining screws (A179215B) and unscrew ring (A48137). Pull out the prism holder assembly.
(Z>) To disassemble the prism holder assembly, unscrew cover (A48138) and two locking screws (BCUX1BC). Compress and withdraw prism spring (A48102) and withdraw prism support (A48103) and prism (A46089). Leave prism supports (A179203) in place. In reassembly, make sure that the prism seats exactly on prism supports (A179203) and that prism support (A48103) seats exactly on the prism. Cork pads (A46399) should be shellacked if necessary.
b.	Azimuth worm housing assembly.— (1) To remove azimuth worm housing assembly (D28723, fig. 8) from the panoramic telescope after the rotating head has been removed and locating lines have been scribed, remove the three retaining screws (A49945D) and unscrew azimuth worm housing (D43243). In reassembling, seat spring (B138684) and carefully screw the housing on support (D29291) until the original scribed locating lines are reached. Make sure that pinion (B138656) meshes with bevel gears (B138655 and B138654) as the housing is screwed up against the spring washer (A48110). If the tops of the gear and pinion teeth come into contact and the gears later slip into mesh, the force exerted by the spring may damage the teeth.
(2) To remove the azimuth worm and worm mechanism—
(a) Unscrew stop (A179192. fig. 6) and azimuth knob nut (A179188). Remove knob (B138643) and micrometer (B138647).
(Z>) Remove taper pin (BFCX1AB) and slide micrometer adapter assembly (B138764) off the worm shaft to which it is keyed.
(c) Slide index assembly (B138753) and worm shoe assembly (B138758) off the worm shaft.
() Loosen the screw (BCUX2CA) and unscrew the retainer (B173995). Remove the spring washer (A185299). Loosen the four screws (A185296) and withdraw the prism support assembly (C79327) after marking its location in the housing (B173993).
() The prism support assembly may be improperly meshed with respect to the rotating head. This will cause the image to lean, or depart from the erect position. (See (3) below.)
(--
PRISM, ASSEMBLY-8136669—। PRISM-A45499
SUPPORT, PRISM, ASSEMBLY-C79327—t-SUPP0RT-C79326 J
&QREW-AI85498--------------------
(SHOWN 90- OUT OPPOSITION)
SCREW-AI85296---------------------
PAD -A185298---------------------
COVER-8173994---------------------
WASHER-AI85299-------------------
GEAR, MITER-C70I5I
------SCREW-8CGX3D0 (shown out of position)
------SOCKET- AI85294
------PIN-BFDXIAC PHOWN OUT OPPOSITION)
SCREW-BCUX2CA
RING-A48I24 EYELENS-A48096 SEPARAT0R-A48I23 LENS.FIELD-A48095 CELL-A48II8
Figure 8.—Panoramic telescope M8—section A—A.
SHIELD-81386
FILTER, ASSEMBLY-8138670 FILTER, ASSEMBLY-8138671
SCREW-BCUXICH
— SLEEVE-AI7920I
---RING-A48I22
-----SCREW- BCUX2BA
------CELL-B 138700
— SCALE-8137176
T ADAPTER, ASSEMBLY-BI38752 A0APTER-C70I52
— RING-A48II9
-j-RETICLE,ASSEMBLY-8138756 ^RETICLE-A48093
—SCREW-BCUXIBA
— RING-A48II7 - SCREW-A49945B - RETAINER-8173995
RAPD 7137
appear to be centered. Deviation should be not more than 3 minutes.
(Z>) A target may be set up for this check, consisting of a horizontal and a vertical cross line inclosed in a circle 1714 inches in diameter,
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PANORAMIC TELESCOPE M8	12
at a distance of 275 yards from the prism support assembly. Center the collimating telescope reticle on the center of the target. When the prism support assembly is interposed in the line of sight, the reticle center will remain within the target circle if the deviation is less than 3 minutes.
() above may be utilized. This arrangement may also be used for further tests.) Sight on the target. If the image leans, one of the following adjustments is to be made :
(a) Unscrew the adapter assembly (B138752) and disengage the prism housing assembly from its meshing with the gear assembly (B138760). Move the prism housing assembly clockwise or counterclockwise one tooth, or more if necessary, to bring the image to erection. If adjustment of less than one tooth spacing appears to be required, loosen two adjacent screws of the four adjusting screws (A185296), insert a thin-rod into one of the two small holes in the face of retainer (B173995) and push the prism support assembly in the desired direction. Reassemble. Recheck for erection and for possible play or binding.
(&) An alternate method may be employed. Remove the spring pressure on the azimuth worm and gear by withdrawing plug (A48595) and spring (A179194). Unscrew the housing assembly (D28723) from the support assembly (B138757), after withdrawing the locking screws (A49945D). Separate the housing assembly sufficiently from the support assembly to draw the bevel gear (B138655) out of mesh with the pinion (B138656). With telescope erect, turn the rotating head until the field of view is erect. A plumb line or some vertical or horizontal line may be used as a target. Reassemble. Recheck for erection and for possible play or binding.
(4)	Eccentric rotation of prism support assembly.—To test the adjustment of the prism support assembly (fig. 10(2)) on the spherical
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ORDNANCE MAINTENANCE
surface of the miter gear use the arrangement described in (3) above.
(«) In order to determine whether the target remains stationary or travels in a circle around the reticle center of the field of view, rotate the telescope in regular intervals of 45°. At the same time, rotate the azimuth testing fixture 45° in the opposite direction. The position of the reticle cross lines and the image should be sighted at 45° intervals for two complete revolutions of the rotating head. Two revolutions of
Figure 9.—Azimuth testing fixture.
the rotating head equal one revolution of the erecting prisms. On beginning the second revolution of the rotating head, move the telescope through 221/2° for the first interval to avoid duplication.
(&) If the target does not remain stationary, remove the four plugging screws (A185498) in the elbow. Adjust the four adjusting screws (A185296) (through the plugging screw holes) so as to reduce the circle traveled by the image.
(