TM 9-1556
19-20
ORDNANCE MAINTENANCE-OBSERVATION TELESCOPES M48 AND M49
19. CARE OF OPTICAL PARTS.
a. To obtain satisfactory vision with Telescopes M48 and M49
it is necessary to keep the lenses clean and dry. Care must also be
exercised in handling the telescopes to prevent damage to, or dis-
arrangement of, the optical system. The instruments should not be
jarred or handled roughly, and under no condition should they be
dropped.
b. Under ordinary conditions, lenses can be cleaned sufficiently
with lens tissue paper. If there is dust on the lenses, remove it by
brushing lightly with camel's hair artist brush, and tap the brush
against a hard body to knock out small particles of dust that cling
to the hairs. Repeat until all dust is removed. Do not attempt to
clean or wipe the lenses with the fingers or a cleaning cloth; and
under no conditions will polishing liquids, pastes, or abrasives be used
for cleaning polished lenses.
c. To remove oil or grease from the lenses, apply liquid lens-
cleaning soap with a piece of lens tissue paper. Wipe off and polish
with another piece of tissue.
d. When liquid lens-cleaning soap is not available, ethyl alcohol
may be used for cleaning the lenses. It is important to use the alcohol
very sparingly, as it reacts on the cement used to hold the lenses to-
gether and will damage the lenses unless used sparingly and wiped
off quickly. Apply ethyl alcohol with a camel's hair artist brush, and
wipe dry with a piece of lens tissue paper.
e. When ethyl alcohol is not available, breathe heavily on the
lens to moisten and wipe dry as directed above. Repeat the operation
several times until all traces of oil have been removed.
20. CARE OF MECHANICAL PARTS.
a. To obtain satisfactory functioning of the mechanism in Tele-
scopes M48 and M49, the mechanical parts should be kept clean and
lubricated if necessary. When assembling the parts, apply special
lubricating grease sparingly to the threads, but take care that grease
does not get on the lenses. An occasional light application of grease
to the threads in the focusing nut and focusing sleeve, and to the
adapter in the focusing mechanism will help to keep the instruments
functioning properly.
(1) OIL, lubricating, for aircraft instruments and machine guns,
is to be used on ball and socket joints of Tripods M14 and M15, and
for screw threads in leg, cradle, and collar assemblies of Tripods M14
and M15.
