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28mm Pretoria

Started by djscobel, 06/18/2004 12:53PM
Posted 06/18/2004 12:53PM | Edited 06/18/2004 02:43PM Opening Post
I was just wondering how many of you own and use the 28mm Pretoria eyepiece that University Optics sold several years ago. I own one and love it - I've never felt the need or even desire to replace it with anything "better". It was one of the first (the first?) coma-correcting eyepieces. In my 13" f/4.5 stars are sharp to the edge, although not a real wide FOV and some significant field distortion. At 28mm and with an f/4.5 it gives an exit pupil just over 6mm, which is plenty big for me. It gives great low-power views in that scope.

I don't see many (if any at all) for sale on AM, so I assume that folks who own them feel the same as I do. I'd be interested in hearing comments from any of you who own one.

Regards,
Doug
Posted 06/20/2004 06:42AM #1
I've tried one thanks to Chuck Hovatter, who loaned it to me just so I could try it. I've also read the article. My only complaint was the field curvature. The designers argued in the article that up to x amount (the exact amount I do not recall--I want to say 1 diopter) was okay, and the eyepiece did seem to have about the amount they designed in. Unfortunately, for me it was just more than I would like. I don't like focusing the edge at infinity and accommodating the center of the field, so in using the eyepiece I was continually tweaking the focus. I didn't have a chance to compare the two, but with or without coma correction, I strongly suspect a 24mm Panoptic would outperform it to my eyes in my 10" f/5. The only thing I can say for certain at this late date is that my test drive of the Pretoria didn't leave me wanting one, and when I got a 24mm Panoptic I was entirely satisfied with it. YMMV.

One suspects that there is a niche market for affordable coma-correcting eyepieces, but the Tele Vue Paracorr has to some degree removed the large Dob market, and it must be hard to work up the courage even to try to service the remnant with specialized eyepieces, as it is just a fraction of a fraction of the overall eyepiece market. Nevertheless, there are plenty of smaller Dobs for which a Paracorr is a para-pain because of its weight and possibly in-focus requirement (potentially troublesome for optimized Newts with low-profile focusers).
--
Mike