Designed by Alan Gee and Roland Christen, the Alpine Astronomical Alan Gee Mark II Telecompressor can be used to effectively speed up your 8" and larger Schmidt-Cassegrain telescope's (SCT's) focal ratio while flattening and widening the field of view.
By nature of their design, SCTs suffer from narrow fields of view and slow focal ratios of around f/10—making them less than ideal for astrophotography and imaging. This telecompressor was specifically designed with 7-layer anti-reflection multi-coated air-spaced doublet achromatic lenses to maintain image brightness and resolution while speeding up the optical tube assembly for better imaging results with shorter exposure times. It also improves the view by widening and flattening it as well as correcting spherical aberration and astigmatism.
To accommodate different viewing and imaging applications, it has been engineered so it can be reconfigured for optimum results when used with different optional accessories. For those who wish to use the telecompressor with binocular viewers, the manufacturer recommends it to be used only with Baader Planetarium, Zeiss, and Celestron models; it should not be used on Meade SCTs with a native f/6.3 focal ratio.