Quote:
Originally Posted by MLParkinson
Marc, I’m amazed at the quality of the stars across the field with a GSO 8 inch f/4 scope. These are very cheap scopes but seem to deliver amazing performance. I assume that you are using a Baader coma corrector or similar?
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Thanks Murray.
TBH, they're not crash hot mechanically with the standard bog focuser, spider vanes, etc... even the primary cell is chonky. The good things about this one are the optics and the CF tube. Now I did a lot of work on it.
Modified the primary cell mirror mounting, changed the spider vanes to stronger ones, the focuser is a low profile moonlite, I also have David's excellent digital focuser control. At F/4 you need it. Even with the CF tube this thing will go out of focus pretty quickly for every degree drop in temperature.
Now for the flat field. Well, it's pretty curved (20%) and also comes with coma, no astigmatism. I'm now about 90% there with my spacing. Still some coma on the extreme corners. Only on one side now thought so just residual tilt to sort out to center the field. Good news is that collimation is rock solid. Doesn't budge in different parts of the sky and that's what matters. The rest of the corner stars, well I crop out or I fix with startools for now.
On axis is pretty damn good. Ray (Shiraz) will tell you the same thing.
MPCC Mark III yeah, although I sold my Mark I a while ago. Honestly I couldn't tell the difference between the two.
PS: forgot to add, all the plastic light baffles inside the tube were lose and not even aligned so I had to reposition them all and glue them. I was getting oblong stars because the aperture wasn't circular. So, yeah, as I say mechanically there's not much QA process when they put them together.