I added the IRF90 Integrated Focuser/Rotator to my CDK17 telescope. Combining this with the PlaneWave Electronic Focuser Assembly (EFA) allows it to automatically obtain pinpoint focus. It takes a series of 5 images at different focal points, analyzes the stars in the image for their full width-half maximum (FWHM), then plots a parabolic curve of focal position vs. FWHM and determines where on the curve is the optimal focus. It then sets the focus to that position. It nails pinpoint focus every time. It can be programmed to check focus at pre-defined time intervals throughout the night. However, the fused silica mirror and carbon fiber truss construction of the optical tube actually hold that focus all night long and I have yet to encounter an instance in which it adjusted the focus.

The rotator rotates the camera to any position angle to compose my images and acquire the best possible guide star. It has an accuracy of 1/1000th of a degree, so I can precisely reproduce the rotation angle of the camera if I come back to acquire more data on any given target or to shoot flats just as they would have been on the night the images were acquired.