Takahashi Mewlon-180C, Instruction Manual, Page: 19 / 24

3. In order collimate the optical axis, adjust
three correcting screws with the 2.5mm
Hex wrench provided. If the axis is out
of alignment as shown in the illustration
at the right, tighten the screw at the right
side, as seen from the tube opening. If
the screw is not positioned in the right
place, tighten the two other screws
positioned near the place. Due to the
mechanical structure for correction,
tighten the correcting screw after the
screw at the opposite side has been
loosened. Repeat this procedure until the
optical axis is collimated. Finally, defocus
and see if the center dot, the intermediate
ring, and the outer ring are seen as a
concentric circle. Then the optical axis
has been perfectly collimated.
* If all three screws are loosened too much,
the secondary mirror holder might detach.
Therefore, loosen these screws little by
little with great care to make certain the
alignment is done and make sure all the
screws being correctly tightened, thus
keeping the secondary mirror attached
firmly in place.
* Sometimes a collimation star image can
move out of field of view when the screws
are moved. When a star image goes out of
the center during the alignment procedure,
continue the alignment, by replacing the
star image with another at the center.
View Field
Loosen this screw
Loosen this screw
Tighten this screw
Tighten this screw slightly
Tighten this screw
from the eyepiece.
from the tube opening.
Tighten these two screws
(refer to the illustration
below)
Tighten these two screws evenly
Loosen these two
screws evenly
"Do not touch the
screw in the center"
If the optical axis is out of
order at the right, correct
it with the correcting
screw at the right
* The center of the diffraction ring might
hardly be seen by the center obstruction
of the secondary mirror.
* The alignment screws are not always
positioned in the desired direction off-
center of the optical axis. Refer to the
diagrams below, where the example of
how to adjust the alignment screws is
shown.