Quote:
Originally Posted by saysme
According to the specs the back focus distance is 70 mm, so an additional 10mm spacer might help?
The scope is collminated using a cats eye collinator and checked using a straight laser collminator, I see the point about focal plane. 2 possibilities really, secondary mirror not square, or the coma corrector itself.
Thanks for help happy to hear more, like can you get a 10-15mm t-piece spacer?
Whats the best way to Make sure the secondary is square?
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One thing at a time. You can't fully judge the image plane problem while there is so much coma. Your 70mm will be made up of the camera (there is a mark on the body on the top left side showing where the image plane is and I'm pretty sure it's 45mm to the front of the camera body). The T-ring will take up between 10-12 mm when fitted. measure that.
The you'll need an adapter of 15-17mm. There are often adapters sold as part of things like the Orion Off-axis Guider, as an example, and they are of varying lengths. Ask around. The other options are to get one made by Precise Parts in Florida (expensive) or by Peter Tan in Hong Kong (much cheaper) - Google him at "Available Astro Gears" and drop him a line. he's very helpful. He made an adapter for me that is able to be screwed in and out, with a locking ring so as to provide between 20-45mm spacing. Give him the measurements you want - say 10-20mm adjustment and tell him a male T-thread (T24 I think it is) on one end a female the other.
Peter