Instruction manual

13
Polarscope alignment
The Reticule
The optical axis of the polarscope is already aligned with
the rotation axis of the mount. The optical axis of the
polar scope can not be adjusted. This is set permanently
at the factory. The reticule in the polar scope must be
centered on the optical axis of the polar scope. When
this is true, the reticule in the polar scope will be parallel
to the rotation axis of the mount. If this is not the case,
accurate polar alignment will not be possible.
Locate Polaris and place it in the center of the
polarscope by adjusting the Altitude and Azimuth of the
mount. Place Polaris directly under the cross in the
center of the reticule (Fig.g-7). Rotate the mount one half
turn about the R.A. axis. Polaris should remain under the
cross in the center of the reticule. If it does not, the
reticule is not centered on the R.A. axis of the mount.
To move the reticule, adjust the three small setscrews on
the polarscope (Fig.g-8). Make small adjustments by
moving only two of the screws at a time. Adjust the
screws to move Polaris half the distance back to the
center of the reticule (Fig.g-9). This is because Polaris
started in the center of the reticule. By rotating the mount
180 degrees, Polaris moved exactly twice the distance
between the center of the reticule and the center of
rotation. The center of rotation lies midway between the
center of the reticule and the new position of Polaris. Do
not turn any of the setscrews more than one-quarter turn
at a time or the reticule will disengage from the
setscrews. Do not over-tighten these screws too much or
the stress could fracture the reticule.
Now re-center Polaris under the cross in the middle of
the reticule using the Azimuth and Altitude adjustments.
Repeat the entire procedure until Polaris remains in the
center of the reticule when the mount is rotated about
the R.A. axis. With some practice, you should be able to
align the reticule with the R.A. axis to within about 2 arc-
minutes. You should never have to make this adjustment
again, unless the polar scope has been dropped,
disassembled, or if the polar scope is to be used on
another mount.
If Polaris is not visible from your area, a distant object
such as the top of a telephone pole, or a distant
mountaintop can be used. These objects are larger than
the image of a star, so they will not provide as accurate
an alignment, but they will not move during this
alignment procedure.
P
olar
is
NCP
O
c
tans
C
a
s
s
i
o
p
e
i
a
B
i
g
D
i
p
p
e
r
Place Polaris here
1
2
E
W
20
20
10
10
0
12
adjust these
screws
Place Polaris here
(half the distance)
If Polaris drifted to here
(diagram applicable to both mounts)
Fig.g-7
Fig.g-8
Fig.g-9