Quote:
Originally Posted by erick
So, should I save my pennies to buy a Paracorr and use it with my el-cheapo eyepieces, rather than attempt to save several times that amount of money to buy a full suite of excellent (but expensive) eyepieces?
Could I indeed make a silk purse out of a sow's ear?
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It's often hard to know which is the predominant aberration in inexpensive widefield eyepieces when used in a short f/ratio scope. Coma is certainly there, but astigmatism is often severe. The traditional "seagulls", or "batwings" that people see as star shapes are definitely astigmatism-dominated. Eyepieces that are fully corrected for astigmatism will seemingly benefit more from coma correction, since the only aberration left is likely to be a tiny amount of field curvature, easily accommodated by a slight focusing change.
But some acquaintances who use inexpensive widefields say that coma correction has often made these eyepieces quite usable and tolerable when coma is removed, so perhaps no change of eyepieces would be required.
I had already gone the route of fully-corrected, expensive, eyepieces in order to eliminate other aberrations when I had an f/10 scope. When I converted to an f/4.9 scope, it was obvious coma was the dominating aberration, and a Paracorr fixed that right up.
I have used one inexpensive widefield (Speers-WALER) in my scope since obtaining the Paracorr, and it was very nice, so perhaps my friends are right that the Paracorr should come first.
The Paracorr provides a small amount of field flattening, coma correction, and a very slight amount of astigmatism reduction (due to the 15% barlow factor). Buying one Paracorr will be less expensive than replacing all your eyepieces.
Just some thoughts.
Don
