Quote:
Originally Posted by Archy
Some people on Cloudy nights report coma with Ethos 21, but not with the ES the Williams 28 or the Pentax 30 XW.
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Coma is a function of the primary parabloidal mirror and not the eyepiece. The only eyepiece that I know of manufactured to correct for coma was the 28mm Pretoria (50deg AFOV I believe). I'm not sure how effective this eyepiece was in different telescopes.
If there is field curvature present then coma is less noticeable and this may be the case with the eyepieces you mentioned above. Magnification too will impact on how easy coma is visible.
As was mentioned previously if money is no object then close second doesn't count. Also anything around 20mm cannot be considered low power or wide field for a 25" f5 so a 31mm Nagler is the best choice if you want 82deg AFOV and almost maximum true field. The only exception would be the 41mm Panoptic for a little more and maximum true field but at the expense of greater exit pupil. Giving 77x and 0.83deg TFOV, the 41 Pan may still be a good option in lieu of the 102x and 0.76deg TFOV of the 31mm Nagler.
At $559 for the 41 Panoptic and $699 for the 31 Nagler thery're a bargain. Consider the fact that several years ago the 31 Nagler was more than the cost of both now.