The optical tube assemblies of the Fastar compatible Celestar and Ultima telescopes are identical to their non Fastar cousins except for differences in their secondary assemblies. The Fastar OTA (or FOTA) has a provision allowing one to remove the entire secondary mirror and holder and replace it with a set of special Fastar optics. The CCD camera (either a PixCel 255 or 237) is then installed into this optics set. This places the CCD camera in a rather odd position in front of the telescopes corrector plate. It should be noted the presence of the camera here, and the correspondingly larger central obstruction it creates, has a negligible effect on image quality. The Fastar optics set also includes a five pound rear counterweight. This weight threads onto the back of the FOTA to help balance the camera. The cost for the optics set and counterweight is approximately $400. Another highly recommended accessory is the Fastar dew shield. This shield prevents the accumulation of dew on the corrector plate, but also serves as a buffer between the camera and any object that may strike it. Because the camera is supported by the glass corrector plate, any force applied to the camera can be fatal. This is of special concern for the owners of fork mounted FOTA's. Allowing the tube to swing down will cause the camera to strike the fork base, potentially breaking the corrector plate. Another concern some people have expressed is collimation problems when returning the secondary to the corrector plate. If the secondary is removed and replaced with delicate precision, it should hold collimation. Once you start imaging at f/1.95, you may seldom need the secondary again anyway!
Switching to Fastar mode is a simple, albeit delicate, procedure. The thumbnail images below detail the process.
