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Owner's of the Celestron Telescope 52291 gave it a score of 0 out of 5. Here's how the scores stacked up:
To verify collimation, view a star near the zenith. Use a medium to high power ocular —
12mm to 6mm focal length. It is important to center a star in the center of the field to
judge collimation. Slowly cross in and out of focus and judge the symmetry of the star.
If you see a systematic skewing of the star to one side, then re
-
collimation is needed.
To accomplish this, you need to tighten the secondary collimation screw(s) that move the
star across the field toward the direction of the skewed light. These screws are located in
the secondary mirror holder (see figure 8-1). Make only small 1/6 to 1/8 adjustments to
the collimation screws and re-center the star by moving the scope before making any
improvements or before making further adjustments.
To make collimation a simple procedure, follow these easy steps:
1. While looking through a medium to high power eyepiece, de-focus a bright star
until a ring pattern with a dark shadow appears (see figure 8-2). Center the de-
focused star and notice in which direction the central shadow is skewed.
2. Place your finger along the edge of the front cell of the telescope (be careful not
to touch the corrector plate), pointing towards the collimation screws. The
shadow of your finger should be visible when looking into the eyepiece. Rotate
your finger around the tube edge until its shadow is seen closest to the narrowest
portion of the rings (i.e. the same direction in which the central shadow is
skewed).
3. Locate the collimation screw closest to where your finger is positioned. This will
be the collimation screw you will need to adjust first. (If your finger is
positioned exactly between two of the collimation screws, then you will need to
adjust the screw opposite where your finger is located).
4. Use the hand control buttons to move the de-focused
star image to the edge of the field of view, in the same
direction that the central obstruction of the star image is
skewed.
5. While looking through the eyepiece, use an Allen
wrench to turn the collimation screw you located in step
2 and 3. Usually a tenth of a turn is enough to notice a
change in collimation. If the star image moves out of the
field of view in the direction that the central shadow is
skewed, than you are turning the collimation screw the
wrong way. Turn the screw in the opposite direction, so
that the star image is moving towards the center of the
field of view.
6. If while turning you notice that the screws get very
loose, then simply tighten the other two screws by the same amount.
Even though the star pattern appears the same on both sides of focus, they are asymmetric. The dark
obstruction is skewed off to the left side of the diffraction pattern indicating poor collimation.
A collimated
telescope should
appear symmetrical
with the central
obstruction
centered in the
star's diffraction
pattern.
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