Quote:
Originally Posted by Shiraz
as far as I can tell, the RCC1 has almost no effect on the location of the focal plane in my system - it just fixes coma and curvature and everything else stays the same. ie if you set it up without the RCC1 and then drop it in, the focal plane does not move much.
If you had 40mm spacers and the focuser wound right in, then you need a little bit more spacing. From rusty memory, I needed to cut 55mm off the OTA of my 250/f4 to get the mirror far enough up to get focus on my QHY8/MPCC - that would be consistent with you needing a bit more extension on your mirror spacing (about 20mm possibly). My SW CF 250f4 has the focal plane a long way out by design and I only needed to take about 15mm off that tube. Cutting the tube is the best solution from a stability point of view, and suggest that you consider doing that when you have worked out how much is needed.
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Hi Ray,
Thanks - I want to cut the tube but not before I find out
the correct focus point for the mirror.
The tube is carbon fiber so it's an expensive mistake if I cut it incorrectly.
I was actually going to use another - better - mirror holder.
This one was only supposed to be for testing.
Another mirror holder could require all of the carbon fiber tube.
cheers
Allan