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2
Put a tiny dot at the center of the optical axis of the secondary mirror (offset
3.8mm from the center of the elliptical secondary mirror, refer to the Figure 2) by using a
template below. A size of the dot should be about 1mmm to 2mm in diameter.
3
Return the secondary mirror holder with the mirror to the original place, and
tentatively fix it with the fixing bolt lightly. At this stage do not touch the other three
adjustments screws on the secondary mirror holder.
4
Draw a circle with diameter of 55mm on a black paper to make a disc. Open a pin
hole of about 1mm to 2mm at the center of the disc. Cut out of the disc and place it into
the change-over ring shown in the Figure 1.
5
Using a Sight tube or Cheshire eyepiece and attach it to the visual back of the
focuser to look at the secondary mirror surface through the pin hole. You can see the dot
on the secondary mirror shown in the Figure 3. Check if the dot moves up and down in
the field of view of the pin hole when you move the secondary mirror holder to the left and
right-hand direction a little. When it occurs, the dot may not be written in the center of the
optical axis correctly. Return to the procedure 2.
6
Assuming that cross hairs are put in the field of view shown in the Figure 3, check
which side on the vertical Y axis of the imaginary cross hairs the dot can be seen. If the
dot is just on the line of Y axis, you can proceed to next step. If the dot is seen on the
left-hand side, it means that the secondary mirror is somewhat distant from the primary
mirror. If the dot is seen on the right-hand side, it means that the secondary mirror is
somewhat close to the primary mirror. Please make sure that you return all the washers to
the same place as they are.
7.
Next, check which side on the horizontal X axis of the imaginary cross hairs
the dot can be seen. If the dot is just on the line of X axis, you can proceed to next step. If
the dot is seen above of the line, it means that the secondary mirror comes near
the upper side shown in the Figure 5. In this case loosen the collimation screw "C" and
tighten the screw "B" on the spider shown in the Figure 4. If the dot is seen below of the
line, loosen the collimation screw "B" and tighten the screw "C" oppositely.
7
Confirm that the dot is seen at the center of the imaginary cross hairs in the field
of view. Remove the disc from the change-over ring.
8
Rotate the secondary mirror holder so that each of distances "a" and "b" becomes
equal shown in the Figure 6. Now fix the secondary mirror holder tightly.
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