Spotdiagram Hypergraph - Schmidt-Cassegrain

Lets first examine the usability of a 16" f/10 Schmidt-Cassegrain for medium format astrophotography. 

Spotdiagram 16" SC f/10

The star-points have a size of up to 400 microns. That is much more than can be accepted even in bad seeing conditions. A Schmidt-Cassegrain can not be used for fields larger that about 20mm diameter if high performance is needed.

Spotdiagram 16" Hypergraph f/8, same box size as above

Lets now compare that SC-desaster with the spotdiagram of our 16" Hypergraph. The Hypergraph shows spot-sizes of less than 30 microns. Since the focal length is about 125", this equals about 2 arc seconds. On a 30"x25" print, spot sizes will still be less than 500 microns !