Quote:
Originally Posted by mental4astro
I'm glad you mentioned coma & the paracorr in one breath, astro. You answered a question I've had about coma correctors and their part in correcting for astigmatism- they don't! I had suspected this when trying out a Baader MPCC, and the astigmatism was still there, but no coma  . |
The Televue Paracorr does give some astigmatism improvement by virtue of slowing the light cone a little - your f/4.5 effectively becomes an f/5.2 (magnification, focal length are increased by 15%).
Field curvature is also reduced; I don't know if thats purely a result of the increased focal length (and therefore longer effective radius of curvature) or if the Paracorr was designed to reduce field curvature. In any case, reduced field curvature is glaringly obvious in some eyepieces.