Celestron STAR HOPPER Instruction Manual page 15

Newtonian collimation views as seen through the focuser using the collimation cap.
Figure A: With the collimation cap in, if you cannot see the entire primary
mirror reflected in the secondary mirror, the secondary mirror will need
adjustment. To do this, adjust the secondary collimation screws by alternately
tightening and loosening them until the outer edge of the primary mirror is
reflected in the secondary mirror and the dark ring of the collimation tool is
centered in the secondary mirror.
Figure C: With both mirrors aligned you should see the silhouette of the
secondary mirror positioned in the center of the primary mirror.
Figure B: Now that
you can see the entire primary mirror reflected in the
secondary mirror, you will notice that the secondary mirror
is not perfectly centered in the primary mirror. To correct
this, you must adjust the primary collimation screws located
at the bottom of the primary mirror cell (see figure 3).
Figure D: After removing the
collimation cap, you should see your eye reflecting back at you from the
center of both mirrors. Collimation is now completed.
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