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Before you begin the collimation process, be sure that your telescope is in thermal equilibrium with the surroundings. Allow 45
minutes for the telescope to reach equilibrium if you move between large temperature extremes.
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.
Figure 7-5
A collimated telescope
should appear
symmetrical with the
central obstruction
centered in the star's
diffraction pattern.
To accomplish this, you need to tighten the secondary collimation screw(s) that move the star acro
direction of the skewed light. These screws are located in the secondary mirror holder (see figure 7-3).
1/8 adjustments to the collimation screws and re-center the star by moving the scope before making
Figure 7-4 -- 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.
ss the field toward the
Make only small 1/6 to
any improvements or before
ttern with a dark shadow
e central shadow is skewed.
orrector plate), pointing
to the eyepiece. Rotate
the rings (i.e. the same
ch the central shadow is skewed).
5. While looking through the eyepiece, use an Allen wrench to turn the collimation screw you located in step 2 and 3.
limation. If the star image moves out of the field of view in
l shadow is skewed, than you are turning the collimation
ews by the same amount.
7.
d
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 pa
appears (see figure 7-4). Center the de-focused star and notice in which direction th
2. Place your finger along the edge of the front cell of the telescope (be careful not to touch the c
towards the collimation screws. The shadow of your finger should be visible when looking in
your finger around the tube edge until its shadow is seen closest to the narrowest portion of
direction in whi
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.
Usually a tenth of a turn is enough to notice a change in col
the direction that the centra
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.
If while turning you notice that the screws get very loose, then simply tighten the other
two screws by the same amount. Conversely, if the collimation screw gets too tight,
then loosen the other two scr
6.
Once the star image is in the center of the field of view, check to see if the rings are
concentric. If the central obstruction is still skewed in the same direction, then continue
turning the screw(s) in the same direction. If you find that the ring pattern
is skewed in
a different direction, than simply repeat steps 2 through 6 as described
above for the new
irection.
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