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Figure 3: On the left is the 2” adapter for the CDK12.5 attached to the Secondary Spacer and the Ronchi
Ocular. On the right is the 2” adapter for the CDK20 attached to the Secondary Spacer and the Ronchi
Ocular.
Step 1, Rough Collimation:
Put the Secondary Spacer into the 2” adapter. The CDK12.5 2” adapter has thumb
screws and the CDK20 2” Adapter has two 8-32 set screws which requires a 3/32 Allen
wrench. Place the 2” adapter into the telescope focuser. Now place a low power 1-1/4
ocular into the secondary spacer (25mm to 40mm). Point the telescope at a bright star.
Defocus the star until it becomes a donut looking ring. If the donut hole looks centered
(in the center of the donut), proceed to Step 2. If the donut hole is not centered, adjust the
collimating screws on the back of the secondary mirror so that the defocused star moves
in the direction of the fat side of the donut as shown in figure 4. Re-center the star and
repeat this process until the donut hole looks centered as shown in figure 5.
Figure 4: This is an example of what you would see in a low power eyepiece that is out of focus for an out
of collimation telescope. To collimate this telescope you will want to adjust the secondary collimating
screws so the out of focus stars moves in the direction of the arrow.
