Hi all. I'm having some serious field curvature issues with my William Optics Gran Turismo 81. I have the WO Flat 6AII adjustable field flattener/reducer and have set it to roughly 7.9mm like the sales page suggests (https://agenaastro.com/william-optics-0-8x-reducer-adjustable-field-flattener-6aii-p-flat6aii.html), but the stars are still very oblong in the corners. I experimented last night for about 3 hours, moving the field flattener about a full rotation in each direction from my starting point but didn't see much difference in the curvature at all.
This is causing a lot of problems when trying to stack subs that are on different sides of the meridian flip. The curvature is different in each corner so the stars don't line up well when the camera is rotated 180°. It gets even worse when I try to align my narrowband frames in Photoshop. For example, I took Ha and OIII before a flip, and SII afterwards. After aligning them, stars in the corners are biased towards red (SII) or green/blue (Ha/OIII) depending on how misaligned they are from each other.
I can see the benefit to a camera rotator here, but I feel like that's a band-aid.
Can anyone lend some advice? Am I maybe just expecting a perfectly flat field that I will just never get?
Thanks!
This is causing a lot of problems when trying to stack subs that are on different sides of the meridian flip. The curvature is different in each corner so the stars don't line up well when the camera is rotated 180°. It gets even worse when I try to align my narrowband frames in Photoshop. For example, I took Ha and OIII before a flip, and SII afterwards. After aligning them, stars in the corners are biased towards red (SII) or green/blue (Ha/OIII) depending on how misaligned they are from each other.
I can see the benefit to a camera rotator here, but I feel like that's a band-aid.
Can anyone lend some advice? Am I maybe just expecting a perfectly flat field that I will just never get?
Thanks!
