Hyperstar is also hypersensitive to backspace.
Strangely I found that Green and Blue needed a different back space than Red even though my filters are supposed to be parafocal. It takes quite some time, but the methodical approach is the best. First I align the corrector plate, then starting with no spacer, I focus just in the center of the image, and take some photos. I add about 0.5mm of spacer, focus in the center and take a few photos. I name the directories where the photos are stored with the backspace distance and filter color. For collimation I make sure that the hyperstar is very flat using a dial gauge, then check for camera tilt. I don't have any so I then align the corrector using the SCT's adjustment screws. When all the star elongation is pointing to the center, it's aligned. I do the alignment first of course. After all of this I look at the photos in the different directories and select the spacer distance where the stars in the corners are the most perfect.
- Astronomik G / B: 11.28mm
- Astronomik R: 13.82mm (11.46 seems good....)
- Baadrr Ha SII: 11.46
- Baadrr OII: Maybe more than 11.46, try 11.75
Here's the different results:
https://photos.app.goo.gl/bBFrQ6nP8yGeyFeBA
Green 10.8mm
Green 11.28mm
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