Instruction manual

13
Collimation
The optical performance of most Newtonian reflecting telescopes can be optimized by collimating
(aligning) the telescope's optics, as needed. Poor collimation will result in optical aberrations and
distortions.
Before collimating your telescope, take time to familiarize yourself with all its components, using the
diagram in Figure 5. The primary mirror is the large mirror at the back end of the telescope tube. This
mirror is adjusted by loosening and tightening the three screws (A), located 120 degrees apart, on the rear
cell of the telescope tube (See Figure 12). The rear cell also has three mirror support screws (B), that are
finger tightened to hold the mirror in one place when transporting the telescope. The support screws need
to be loosened before adjusting the collimation screws.
The secondary mirror (the small, elliptical mirror under the focuser) also has adjustment screws. To
check the collimation of your telescope, point the front of the tube toward a bright wall or blue sky (never
point your telescope at or near the sun) and follow the directions below.
Aligning the Secondary Mirror
If you have an eyepiece in the focuser, remove it. Rack in the focuser tub completely, using the focusing
knobs, until the draw tube is no longer visible. You will be looking through the focuser at a reflection of the
secondary mirror, projected from the primary mirror. During this step,
ignore the silhouetted reflection from the primary mirror. Insert the
collimating cap into the focuser and look through it. With the focuser
pulled in all the way, you should be able to see the entire primary mirror
reflected in the secondary mirror. If the primary mirror is not centered in
the secondary mirror, adjust the secondary mirror screws by alternately
tightening and loosening them until the periphery of the primary mirror is
centered in your view. DO NOT loosen or tighten the center screw in the
secondary mirror support, because it maintains proper mirror position.
Aligning the Primary Mirror
Now adjust the primary mirror screws to re-center the reflection of the
small secondary mirror, so it is silhouetted against the view of the primary.
As you look into the focuser, silhouettes of the mirrors should look
concentric. Repeat steps one and two until the mirror reflections appear
concentric.
Remove the collimating cap and look into the focuser, you should see the
reflection of your eye in the secondary mirror.
A
A
A
B
B
B
Figure 12 - (A) Collimation screws
(B) Mirror Support Screws
Secondary
Collimation Screws
Figure 11 – Secondary
Collimation Screws