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Step 3: Setting the Primary-to-Secondary Spacing:
The primary-to-secondary spacing is set at the factory. You will typically not need to adjust
this unless the secondary has been moved.
For your CDK optical system to perform as well as it should, the spacing between the
primary mirror and secondary mirror should be set to an accuracy of +/- 1mm! Fortunately,
you won’t have to directly measure this spacing. When the primary-to-secondary spacing is
set correctly, the focal plane will land at an exact known distance behind the fully racked in
focuser. The Ronchi Adapter and Spacer places the Ronchi grating of the Ronchi Ocular
precisely where the focal plane is supposed to be.
Collimation knobs
Central Secondary Spacing Bolt
For the CDK12.5 there are four collimation screws and a central
bolt used for spacing
