Anyone who claims that standard SCTs are free of coma is someone who has never looked through an SCT or is simply unable to see it.
If the question is actually, "does a Celestron SCT have coma," and we can't come to a solid answer here, I don't know what else can be said.
The fact that SCTs have off axis coma is common knowledge and for those that use the scopes.
It is a know, accepted, and well documented fact by SCT imagers and those doing photometry with moderate sized detectors on SCT telescopes. It is known and documented by manufacturers of the scopes and by manufacturers of correctors for SCTs.
Page four of the Celestron edge hd white papers shows spot diagrams for the standard sct, Meade acf, and edge hd telescopes. The standard sct spot diagrams can be verified with a single exposure image using a full frame camera in a sct is representative if what I have experienced with the many years imaging and doing photometry with a c925.
If this can not be agreed upon I'm not sure what can be...
I've owned several SCTs over the years, and they all had coma--not bad, like an f/6 newtonian, approximately. And using a focal reducer/field flattener only makes it more obvious. Kudos to Celestron for the Edge design, designed, of course, to correct the edge, LOL.
Edited by Starman1, 24 September 2023 - 11:31 AM.