Quote:
Originally Posted by NightCal
My present imaging set up produces a degree of field curvature. What I need is a field flattener. The trouble is that equals money and at the moment I don’t have as much I want for buying astro stuff. (do I ever?)
Looking at the effects of field curvature on the image it strikes me that this looks very similar to star trailing, except that the direction of trailing varies with angle and the amount of trailing varies with distances from the centre.
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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.