I have the Lumicon coma corrector, bought it used about ten years ago for a song. It is optimized for f/4.5, but shows moderate improvement with f/4 to f/5 systems. I never need it on anything I own slower than f/5. Just about any fast mirror has some coma. It is made more apparent using wide-field eyepieces, sometimes disappears completely with more mainstream eyepiece designs such as Plossls & Orthos. If you use TV eyepieces, I would suggest the TV coma corrector, otherwise use a more "mundane" eyepiece line, with a field that lies inside the coma-free zone (or at least shuns the outer, most offensive areas). My comments are for visual use. I"ve never used the Lumicon unit for imaging, so I can't comment on whether the field is truly flat. Too, coma is usually only apparent at very low powers. Don't think of it as mirror "flaw", think of it as a mismatch between the mirror and your eyepieces. --- DunnDave@aol.com wrote:

Does anyone have any expirience with Coma Correctors? My newly completed 16" f/5 has coma. I would appreciate any advise anyone might have on how to deal with coma. The Lumicon and TelVue correctors are several hundred dollars so I don't want to just buy one to experiment.

Thanks. Dave

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Hi Dave, Dave Bernson and I were very pleased with the Paracorr purchased for the 20" f/4 Galaxy Optics dobsonian we built back in '88. (I'm not familiar with the lumicon coma correctors.) We used it for several years without any correction but the Paracorr is now nearly mandatory with low to medium powers. You could super-glue it in and you'd be happy. Dave has a set of the Type 2 Naglers (12mm, 16mm, & 20mm) so keep in mind we were using a Televue product with Televue eyepieces. A few months ago we held an impromptu eyepiece comparison in my front yard comparing an 11mm Nagler Type 1, a 12mm Type 2 & 4, and a 14mm Meade Ultra Wide. Because I have a 10" f/5 dob, Dave also brought the paracorr to see what improvement there would be. As I recall, the Paracorr wasn't terribly needed (though improved) at the 100 power level but when we put in a 20mm nagler at 64x the correction was obvious. I'm sure we could arrange some way for you to try out the paracorr before you purchase anything. Hope this helps a bit, Dave Bennett (801)583-3295 On Tuesday, Sep 16, 2003, at 11:09 US/Mountain, DunnDave@aol.com wrote:

Does anyone have any expirience with Coma Correctors? My newly completed 16" f/5 has coma. I would appreciate any advise anyone might have on how to deal with coma. The Lumicon and TelVue correctors are several hundred dollars so I don't want to just buy one to experiment.

Thanks. Dave