William Optics 2" UWAN Series Eyepiece - 28mm

5.0 28mm UWAN Performance

Huge true field of view,Sharp images

Eye position not perfect,Very Big Heavy

I started looking seriously for an Ultrawide angle eyepiece with excellent performance when I acquired a 16" Meade Lightbridge. At F/4.5 my 40mm WO Swan eyepiece wasn't going to work well - an 8.9mm exit pupil was just too much waste of light gathering. I considered a 26mm Nagler but decided it was just too expensive. I chose the William Optics 28mm UWAN which was available for about half the price of the 26mm Nagler. I knew that coma would be a problem with a wide FOV eyepiece on the 16" F/4.5. The WO specs are a bit off on the effective field stop size for this eyepiece - I calculated it at 39.4mm which is still very large. I went ahead and purchased a Baader MPCC (coma corrector) and the appropriate rings to use it with the 28mm UWAN.

The 28mm UWAN is an exceptionally well corrected eyepiece - I could tell right away from the views through my 4" F/7.7 refractor. Stars are perfect all the way to the edge of the field of view. Contrast is excellent and no ghosting was noticeable even on the Moon. When used with the 16" F/4.5, a coma corrector is a requirement with 28mm UWAN. Without the coma corrector anything beyond the inner 1/3 of the FOV shows noticeable coma. I have 20mm T5 Nagler and its performance is similar (about 1/2 the FOV is usable, the rest shows coma). The worse performance of the 28mm UWAN is to be expected since it has a much larger true field of view compared to the 20mm Nagler. Fortunately the Baader MPCC does an excellent job of eliminating coma. The MPCC / 28mm UWAN combination yields pinpoint stars all the way to the edge of the field using a 16" F/4.5. One of my favorite things to do with the 28mm UWAN is attach the MPCC and an OIII filter and cruise the Summer Milky Way. The Veil, Crescent, Swan, Lagoon, and Trifid nebulas are all stunning with this combination.

The only issues with this eyepiece are weight (I call it the Kilomonster since it weighs just under 1 kilo or 2.2 lbs) and eye positioning. I don't have a problem with the eyepiece positioning but the eyecup is quite large and you have to turn your head just a bit to look through the eyepiece so some users may have problems with it. The weight is a bit of an issue if your scope is sensitive to balance or if you are using a small scope. Overall though, I wouldn't hesitate to recommend this eyepiece especially considering the bargain price compared to the Nagler alternatives.

This review was provided courtesy of AgenaAstro.com