Quote:
Originally Posted by evltoy
I have been battling this back focus on my C8 with the celestron x0.63 reducer since I ever got it in Jan 2021!
First thing. There is currently 2 celestron x0.63 reducers out there. There is no markings to tell you the difference.
- The old original one which needs 105mm back focus
- And a more recent unit (last 2 years) that needs 85mm back focus.
If you bought new stock in the last year or so it will be 85mm like mine is. Celestron and/or the paper that comes with the reducers doesn't tell you they have changed the back focus after changing glass manufactures. This is why there is so much confusion with users on the new item.
My current setup is now bang on 85mm (measured the extensions (30mm), T-Adaptor (8.5mm) with a vernier caliper) + DSLR (46.5mm). My Camera is a Nikon D600 in APS-C mode and using M42 extensions.
I did my focus with a Bahtinov mask with the star 1/2 way between edge of field and centre of FOV. Also did the recommended finishing the focusing in CCW.
The attached image is a 90 & 120 sub frame I took last night. Guiding through PHD2 was around 0.21, Polar align through SharpCap (0.3arc/sec). Star alignment was perfect.... the best I have ever gotten in a long time.
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Wow thanks for that! Great images.
My stars look identical to yours so I’m guessing it’s a just how it is. I did a quick stack and edit (30mins) this morning and I don’t hate the result. I think I’ll keep on with it and save for an edgehd when the time comes.