You also need to be aware of any reducers, flatteners, filters, and other adapters. Even if the scope supports FF, it is only as wide as it's narrowest chokepoint. And, you may get vignetting no matter what, it just depends on what degree; and what degree of vignetting you can put up with.
Many scopes made with imaging in mind will say what maximum imaging circle (sensor size) they are made to work with. Though I have found that a lot will be vague if it is anything less than full frame. Often it is the more expensive astrographs that support the larger image circles. If a scope supports full frame, that will almost certainly be listed in the marketing.
All of the (newer) William Optics scopes and flatteners that I have will image at full frame.
The EdgeHD 8 is supposed to cover a FF circle, but the reducer is only designed for APS-C.
(I have not tested any of these personally, as all of my cameras are smaller than APS-C.)
The Orion 8" f/3.9 you have in your signature says less than 10% vignetting on APS-C, which is good, but doesn't mention FF at all. I think you can assume that there will be significant vignetting.
The ES ED102 doesn't say either way.
If you have a scope/camera combination in mind, you could try to find other people using it on Astrobin.
Edited by MikeMiller, 19 November 2019 - 04:12 PM.