TM 9-1556
23-24
ORDNANCE MAINTENANCE-OBSERVATION TELESCOPES M48 AND M49
b. All optical elements and metal components should be care-
fully marked or tagged as they are disassembled to ensure correct
positioning in the instrument on reassembly. If parts are not so
marked or tagged, considerable difficulty may be encountered in the
final assembly. Reference marks should be scribed when deemed
advisable. An indelible pencil or diamond may be used for marking
on unpolished surfaces of optical elements. Metal components may
be scribed, marked, or tagged.
c. Defective parts should be replaced from stock. Replacement
of defective optical elements must be carefully checked inasmuch
as replacement of even one optical element may change the optical
characteristics of the telescope and render readjustment necessary.
Replacement of metal components is easily accomplished since the
components are all standardized and available as replacements.
24. DISASSEMBLY OF OBSERVATION TELESCOPE M48.
a. Disassembly of focusing Mechanism.
(1) Remove the eyepiece cover cap (fig. 8). Carefully unscrew
the eyepiece assembly (fig. 8) and wrap it in clean tissue paper.
(2) Unscrew the focusing nut locking screw A204670 (fig. 8).
Unscrew the eyepiece focusing nut sleeve A204664 (fig. 10) from
the focusing nut. Unscrew the focusing nut from the eyepiece focusing
nut tube A204667. Remove the ball and spring from its recess.
(3) Unscrew the focusing tube (fig. 8) from the prism housing.
Slide off the focusing sleeve.
b. Disassembly of Eyepiece Asssembly.
ponents of Observation Telescope M48.
(2) Hold the eyepiece assembly, with the field lens down, and
gently tap around the edges of the cell to release the field lens. Re-
peat the procedure to free the eyelens, tapping more vigorously if
necessary. NOTE: Be careful to hold the eyepiece assembly over
a soft pad or piece of folded tissue when performing this operation. Do
not permit the bare finger or table to come in contact with the pol-
ished surfaces of the lens. After removal, wrap the lens in lens tissue
paper and store in a safe place.
c.
Disassembly of Prism Housing Assembly.
(1) Remove focusing mechanism with eyepiece assembly from
prism housing assembly (fig. 8).
(2) Unscrew the prism housing assembly (fig. 8) from the body
tube.
