Prismatic Telescope

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jHANDBOOK II I

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1repared by the American Expeditionary Forces

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Army War College

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THE GENERAL SERVICE SCHOOLS

LIBRARY

*\u25a0*\u25a0 l-r>7-.*>"1

War Department

Document No. 766

Adjutant General.Office of the



WAR DEPARTMENT,

Washington, February 25, 1918.

The following notes on the "Prismatic FieldMonocular Tele-scope, Type X,Model 1917," which have been adopted by the

American Expeditionary Forces as standard, are published for theinformation and guidance of all concerned.

(062.1. A.G. O.)

order of the Secretary of War,

JOHN BIDDLE,

Major General, Acting Chief of Staff

Official:

h. p. McCain,

The Adjutant General.



TABLE OF CONTENTS

—Handbook for the Longue-Vue Monoculaire A Prisme Type—X (Campagne-Modele 1917) 5

General Description 5

Instructions for use— 6—Section I—Setting1 Setting vp Observation of terrain 6—Section 2 Preparatory operations 7—Section 3 Direction and control of fire 8

Transportation 8

Up-keep 8

Accessories 9

—ptical and other data 9Annexe To read deflection in terms of plateau and tambour 11



HANDBOOK

FOR THE

LONGUE-VUE MONOCULAIRE A PRISMES

Type X

(CAMPAGNE MODELE 1917)

GENERAL DESCRIPTION.

The "lognue-vue monoculaire a prismes" is specially intended

for the observation oftargets

and for the direction and controlof

fire. It is particularly suited for observation at long ranges.

The "Campagne Type X" was designed to replace the 1898model battery telescope and is used withbatteries provided withsights graduated in mils (6400 mils =360 degrees), namely, thefollowing: 75 m/m. guns, 65 m/m. mountain guns, 14 and 145 L

Modele 1916, 155 Lmodele 1877-1914 and modele 1917 Schneider,155 C modele 1915 Schneider, 220 m/m. Schneider howitzer, etc.

The "Type X" telescope comprises 3 eye-pieces A (fig. 2)mounted on a "revolver" B, the corresponding magnifications

are X 15 X 23 and X 30.

The X 15 magnification is used in conditions of low visibility;the illumination of this magnification is better than that of theservice pattern "night telescope."

The X 23 magnification is the one normally used, the illumination being slightly better than that of the 1909 service patternX 8 prism binocular.

The X 32 magnification is found useful in conditions of exceptionally good visibility.

The telescope is mounted upon an elevation movement D carrying a sight clinometer C; it is used on a stand fitted with an azimuth movement (see figs. 1, 2 and 3).

The sight clinometer enables the measurement of angles of sightinmils (6400 mils=360 degrees). —

The azimuth movement comprises two dials -an upper dial,carrying elevation movement and telescope which can be movedover a lower dial by turning milled head T of a tangent screw.Without upsetting the relative positions of upper and lower dialsthe whole instrument can be rotated by turning milledhead S of

lower tangent screw.5



6

There are two graduations:(1) On the lower dial a continuous clockwise graduation (*)

from 0 to 6400 mils, used in conjunction with black index on upperdial. Each division is worth 100 milliemes and intermediatevalues are read on the left-hand side-graduation of the tangentscrew drum. Each graduation of the drum graduation is worth1mil, and it is read in conjunction with the black index mark (theone engraved on smooth ground).

(2) A second graduation on upper dial; this, in conjunctionwith the right-hand side graduation on tangent screw drum being

intended for use specially with75 m/m. and 65 m/m. mountain batteries when angles are measured in terms of "plateau" and "tambour" of the gun-sight. (See Annexe).

INSTRUCTIONS FOR USE.— —§ 1. Setting vp -Observation of Terrain.—

To set up the instrument. -Remove stand and azimuth movement from their case (see that clamp Cis tight). Loosen clamps

of tripod legs and adjust sliding portions to desired height; presseach leg well into the ground. Free the ball-and-socket joint Rof the tripod by turning clamping nut G in counter-clock wise di

rection and bring the bubble to the centre of the spherical levelH; then clamp ball-and-socket joint by turning nut G in clockwisedirection.

Remove the elevation movement from the telescope case; see

that the clamping lever E (fig. 1) of the elevation movement ispressed right down. Fit it onto the pivot lof the azimuth move

ment, seeing that spur J on the latter engages withslot on elevation movement. Tighten clamping lever E. Carefully remove

telescope from its case and fit it into clamping collar.—To observe with the telescope. Remove object glass cover Mand pull out ray shade N—see that the eye-piece which it is de

sired to use is in correct position (turn "revolver" until "catch"is felt). Focus eye-piece by sighting on a distant object and turning milled collar until definitionis at its best. The graduations

onmilled collar are in dioptrics.—To change magnification. Turn revolver until eye-piece of de

sired magnification is in correct position.

Tolay

ona

determinedpoint

withoutmaking angular measure—ments. Loosen clamp C fixingazimuth movement to stand. The

telescope can then be turned freely in a horizontal plane. Elevateor depress as required by milledhead P.

(') Corresponding to the graduation of gun sights with 75 m/m. guns, 65 m/m.mountain guna and the Schneider material mentioned on page 5. Itshould be notedthat in the Schneider gun sights the index is fixed and the graduation movable.whereaa in the 75 m/m. gun sight the "plateau" is fixed and the index movable. But inbothcases an increase indeflection is left deflection.



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—§ 2. Preparatory Operations.

—To measure an angle of sight (in mils). Slacken clamp C and

lay roughly for direction; tighten clamp C and adjust accuratelyby milled head S. Bring the centre of the cross of the micrometeron the target by means of elevation movement P.

Turn the clinometer on the telescope hinge until a "catch" isfelt; bring the bubble of the clinometer level in the centre of itsrun by turning milledhead U.

Read the angle inhundred of mils on the divided disc V (placed

at the side of the clinometer) and the intermediate values on thedrum Z. Black figuring corresponds to positive angles of sight,

red figuring to negative angles. The black and red figures of the

drum Z correspond to the figures of same color on the sector V.To measure the horizontal angle between two points (in mils).—

If the two points come at the same time in the field of the telescope make use of the horizontal scale of the micrometer (see fig.4) each division of which is worth 5 mils.

In the other case proceed as follows set the azimuth movement to zero by turning milledhead T so that the zero on the lowerdial coincides withindex X on upper dial and the zero of the tan

gent screw drum coincides withindex Y. Lay roughly on the left-hand side point by loosening clamp C, tighten c amp C and layaccurately by turning milled head Sof general movement. Nowlay on the right-hand side point by turning milled head T of relative movement (J ). Read angle measured on lower graduation

and tangent screw drum (indexes X and V—espectively).To measure deflection for a given target. Set the azimuth move

ment to zero and lay on target, then lay on aiming point by turn—ing milledhead T. Read off deflection this can be expressedeither as a—true angle as indicated on continuous graduation (o—6400 mils see paragraph headed "To measure the horizontalangle between two points) or in terms of "plateau" and "tambour"(see Annexe).

To lay a gun parallel to a given direction (by reciprocal observa—tions). 1°Using gun-sights withgraduation divided into 4 quadrants and with "zero position" at 100 mils. (75 m/m. and 65 m/mmountain batteries). Station instrument about 50 metres fromgun and lay it in the given direction (target or expected directionof fire) by using clamp C and milledhead S, the instrument being

set to zero. Now lay instrument on gun-sight pillar and read in

terms of "plateau" and "tambour" the deflection which must be

given to the gun. (seeAnnexe).

Lay the gun withthis deflectionon the centre of the instrument.

2° Using gun-sights with continuous graduations divided in

6400 mils withzero position at 0 mils. Station instrument about

(') When itis desired to measure an angle of several hundred mils it is quicker to

throw tangent screw out of action by pressing pallet W right down. The upper dialwillthen turn freely over the lower dial. Before using slow motion see that the screwhas properly engaged— but do not attempt to force it home— turn milled head T andscrew willsoon fillinto gear.



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50 meters fromgun; set the instrument at 3200 mils and lay in thegiven direction by using clamp C and milled head S. Now layinstrument on gun-sight pillar using milledhead T; read off theangle as indicated by instrument. Subtract 3200 if the reading

obtained is greater than or equal to 3200. Lay the gun with thisdeflection on the centre of the instrument.

3° Using gun-sights with graduation in two halves divided in3200 mils in the same direction and withzero position at 1000 mils.Station instrument about 50 metres from gun; set the instrumentat 4200 mils and lay in the given direction, using clamp C and milledhead S. Now lay instrument on gun-sight pillarusing milledheadT; read off the angle as indicated by instrument. Substract 3200if the reading obtained is greater than or equal to 3200. Lay thegun with this deflection on the centre of the instrument.

—§ 3. Direction and Control of Fire.—

To determine the height of burst (in mils). Make use of the vertical scale of the micrometer divided every 5mils. The distance between the dotted line and the zero graticule represents3 mils and is equal to height of the top of the cross above centre—line this angle is the "hauteur type" (the normal height ofburst)

for 75 m/m. guns. —Correction of deflection. The instrument being laid in direction of target, bring the point of burst onto the vertical graticuleof micrometer by turning milled head T. The deflection of gunmust be increased (or diminished) by the angle by which the in

strument reading has increased (or diminished).—Change of target. The instrument being laid on the old target,

direct telescope on the new target turning milled head T. Thedeflection of the gun must be increased (diminished) by the angleby which the instrument reading has diminished (increased).

TRANSPORTATION.

To put the telescope and elevation movement in the telescope— case. Turn the "revolver" until the x15 eye-piece is in positionpush in the ray shade and replace object glass cover. Remove

telescope from clamping collar and place it in its case, object glass

first. Shut clamping collar and tighten up clamping nut. Putthe elevation movement in its case, fasten it in by means of strapand cover it with leather protecting flap. Shut lid and do up

strap. This case is carried either over the shoulders or on theback like a haversack.

To put the tripod and azimuth movement in their case.— -Fold uptripod and insert it in its case, legs first so that feet are in contact

withbottom of case. Close lid and do up fastening strap. Thetripod in its case is carried across the shoulder.

UP-KEEP.

should be very carefullyIt is'essentialithat theTinstrumenthandled*so as to avoid shocks and falls. Cleaning of internal parts



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and dismounting of the dials or telescope are strictly forbidden.Ifnecessary the instrument should be returned for repairs to the"Service G6ographique de l'Armee". External parts only are tobe cleaned. In cleaning a lens, never rubitwitha cloth or anything

which might grease or scratch the glass; breath on the surface and dry immediately by rubbing gently with a piece of fine

linen which is not fluffy. Repeat this until the vapour condensesregularly and evaporates concentrically.

If the ball-and-socket joint does not work smoothly removeclamping nut by first undoing stop screw. Take the ball-andsocket joint to pieces and apply thick grease.

ACCESSORIES.

The accessories include:1reinforced leather case with strap, containing telescope and

elevation movement.1 waterproof-cloth case with leather lining containing tripod

and azimuth movement.

OPTICAL AND OTHER DATA

Magnification about 15, X 23, X3OReal field about 50, 36, 27 mils.Dia. of exitpupil ..about 5, 3, X 23, X 5 mm.

Weight of telescope without case... 3 kgs.Weight of telescope and elevation

movement with case 7 kgs. 500Weight of tripod and azimuth move

ment withcase. 9 kgs.



11

ANNEXE

TO READ DEFLECTION IN TERMS OF PLATEAU

AND TAMBOUR.

When the telescope is used with75 mm. batteries and set up

close to the battery, by using the quadrant graduation on upperdialand the two indexes, V,W of the tangent screw drum the com-mands can be given in terms of "plateau" and "tambour".

"Itshould be noted that when the instrument is at zero, i. c.,when the index X is in linewithzero division of lower graduation,the reading in terms ofplateau and tambour is "plateau: 0", "tambour :100". —To read in terms of "plateau". -One quadrant of upper dial isdivided into 8 sectors marked PLO,P L2, etc., P. L.14. As the

optical axis of the telescope passes through the four quadrants ofthe "cercle fictifde pointage" (fig.5) the quadrant on the upperdialpasses successively over 4 arrow-shaped indexes which fallontheO, 16, 32 and 48 marks of lower (continuous) graduation, whencethe rule:

The "plateau" number is the number of the sector on which oneof the indexes falls (*) (see example fig. 6).

—To read in terms of "tambour". Each sector of the divided

quadrant comprises a

smooth anda

ruledportion. In reading

in terms of "plateau", note in which of this two portions theindex falls and read the tangent screw drum accordingly, i.e., useeither reader V on smooth ground or reader W on ruled ground(see example fig. 6). '

x)(x ) When layinga gun for direction by 'reciprocal sighting" (page 7),the proximityof the gun renders the consideration of the quadrant useless; in this case, itwillbe seenthat the indexes of the gun-sight and the telescope are necessarily brought into oppo-site quadrants.



Fig. 1



Fig. 2,



Fig. 3,



—Figure 4. Micrometer,

The center of the cross indicates the optical axis of theinstrument.Each division of vertical and horizontal scales is worth 5

mils.

The length of any arm of the cross is worth 3 mils. The topof the cross and the dotted line above the zero graticule facili-tate the obtention of the normal height of burst of 3 mils,when the center of the cross coincides with the base of thetarget.



Figure 4

CERCLE FICT^DE POINTAGE

(THEORETICAL SIGHT DIAL)



Figure 5.

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