To adjust a Ritchey Chrétien (RC) we use a slide light chart as an aid.

Product Description
We use a light chart as an aid for adjusting a Ritchey Chrétien (RC).

The uniformly illuminated surface makes it easier to determine the geometry of the focuser, secondary mirror, and primary mirror. Differences in brightness occur at the edges of the mirrors and can be adjusted using a Cheshire adjustment eyepiece.

We perform fine adjustment using our artificial star. The star image is then often tested using Polaris under the real sky.