Quote:
Originally Posted by Steffen
Are you sure it's field curvature you're up against? In the absence of other aberrations field curvature would manifest itself as the inability to bring both the centre and the edge of the field into focus at the same time, i.e. in order to obtain an image that's in sharp focus throughout it would have to be projected onto a curved screen.
What you describe sounds like coma to me. Mind you, I have no astro imaging experience, just speaking in general optical and photographic terms 
Cheers
Steffen. |
Field curvature will also cause elongated stars because as well as the lack of focus, the imaging sensor is effectively tilted in relation to the curved focal plane as soon as you move away from centre field.
You can fix up the elongation in PS. There is a chapter in the book "Photoshop Astronomy" by Scott Ireland which describes how to do it--basically like the procedure described by Frank
Geoff