Chapter XVIII: Part III: The Stalking Telescope

Apart from the regular issue of G.S. Telescopes, there are now
in the B.E.F. about 40,000 or 50,000 more or less high-class
telescopes. These have been obtained from all kinds of sources, from
deer-stalkers, yachtsmen, etc., and the care and use of these glasses
has become a matter of great importance.

CARE AND CLEANING:

The first thing to remember is that the lenses of all telescopes are
made of very soft glass, and that this glass is polished to a very
high degree. A few scratches on the outer surface of the object-glass
will negative the value of the best telescope. When the telescope is
first taken from its case, a light film of dust will usually be found
to have formed on the object-glass. This should be flicked off with
a handkerchief, and if any polishing is necessary, it should be done
with a piece of chamois leather or well-washed piece of four-by-two;
this cleaning material should be free from grit, and should be
carried in a pocket or in the pay-book, where it will be kept clean.
Over 50 per cent. of the telescopes in use, in or about the front
line, have been scratched more or less badly, owing to the neglect of
this simple precaution.

Special attention should be paid to the cleaning of the objective
lens, which is liable to become covered with dust owing to its
position in the telescope and the opening and closing of the draws.

Never on any account touch the glass with the finger or thumb. If
the glass be allowed to get damp, fogging will result. To cause the
fogging to evaporate, remove object-glass and eye-piece, lay the
telescope out in the sun or in a warm room. Never permit the metal
work to get hotter than the temperature of your hand, otherwise the
Canada Balsam (which is used to join the concave and convex lenses in
the object-glass of all high telescopes, except the G.S.) will melt.
If the draws get wet, they must be thoroughly dried and slightly
lubricated. The same applies to the sun-shade. When an officer is
inspecting telescopes, he should inspect the cases also. In screwing
tubes or cells into place, great care must be taken not to damage the
threads. It is often as well to turn the screw the wrong way with a
gentle pressure; the threads will then come into correct engagement,
and a slight click may be heard.

THE GENERAL SERVICE TELESCOPE

As has been stated above, Canada Balsam is not used between the
lenses of the object-glass of the G.S. telescope. When a G.S.
Telescope has been taken to pieces, the only difficulty experienced
in assembling it again will be in the replacing of the lenses forming
the object-glass. To do this two rules must be remembered:

1. The convex lens is always the nearest to the object, and,
therefore, must be replaced first.

2. On the side of the lenses forming the object-glass an
arrow-head will be found cut into the glass.

Before the lenses are put back the arrow-head must be completed,
and the middle of the arrow must be allowed to slide over the
barb or raised line in the cell.

RULES FOR USE:

1. Always extend your sun-shade (more O.P.’s have been given away
by the light shining upon the object-glass of telescopes than
in any other way).

2. Always mark your focus by scratching a circular ring on the
focussing draw. (This will allow you to focus your glass
correctly and quickly before putting it to your eye.)

3. Always pull out or push in the draws of your telescope with a
clock-wise circular motion, and keep them slightly lubricated.

4. Always carry your telescope slung on your body. If you take it
off and let it travel in a lorry or car the jolting will almost
certainly ruin it.

5. Always use a rest when observing.

6. When looking into the sun, make a sun-shade nine inches or a
foot long, to fit on the short sun-shade of the telescope. This
will give you great assistance when the sun is over the German
lines. It is a trick borrowed from the chamois-hunters of the
Pyrenees.

7. Remember that when there is a mirage you will get better
results with a low than with a high power of magnification.
Conditions in France are more suitable to a magnification of
under than over twenty-five. Excellent work can be done in
the front line with a glass that magnifies only ten times.
If the high-power eye-piece is used for any special purpose
when reconnaissance is finished, it should be replaced by a
low-power eye-piece.

8. When searching a given sector of ground or trench divide it
into “fields of view” work slowly allowing each field to
overlap. Never leave any suspicious-looking object without
having ascertained what it is and why it is there.

9. Slight movement is more easily detected if you do not look
straight at the object. Always look, a little left, right,
high or low. Keenest vision is at the edges of the eye. This
particularly applies to dusk or dawn.

10. When your object is found, consider:

(a) Distance.
(b) Shape.
(c) Colour.
(d) Size.
(e) Position.

Use each detail to check other details; for instance, if you can
distinguish the state cockade upon a German cap you may be
certain that you are not more than two hundred yards distant.

11. Do not forget that good results can be obtained on clear
starlight or moonlight nights, by the use of night-glasses or
telescopes, especially if working in conjunction with a Lewis
or Vickers Gun. Generally speaking, the bigger the object-glass
and the lower the magnification the better will be the results
obtainable at night.

12. In trench warfare a really good glass-man working from our
front line by day can make a most valuable wire reconnaissance.

13. Remember that the conditions of visibility are constantly
changing; an object which is indistinct at eleven o’clock may
become quite clear at eleven-five.

14. Always be ready to avail yourself of natural conditions. The
visibility after a rain-shower is almost always good; it shows
up wire and gaps in the wire, paths, ground traversed by
patrols, etc. The best season for “spotting” O.P.’s is autumn,
when the leaves fall and the grass withers.

15. It is a good thing to disguise the whole of the telescope by
use of sandbags or other material around it. Great care must be
taken to ascertain that such disguise is kept free from dust or
grit.