Rubinars are pretty much OK..
I have 10/1000 Macro, I had to relax the main mirror a bit, now it can't be much better..
https://www.iceinspace.com.au/forum/...hlight=rubinar
https://www.strickling.net/russentonne.htm
My Rubinar 500 f8 is not so good, but still usable.
MTO-1000A is very heavy.. but OK
I also have Opteka 500 f/6.3, DG.. bad at corners but OK in the centre of the frame, see here, post #24:
https://www.cloudynights.com/topic/4...3-mirror-lens/
Maybe it is usable for solar eclipses (very light)..
and here:
https://www.iceinspace.com.au/forum/...ghlight=opteka