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William Optics 2" UWAN Series Eyepiece - 28mm

5.0 (1 Reviews) Read Reviews Write Review
Brand William Optics
Part Number E-UWA28

Product Info

Manufacturer Description

Beautiful Ultra Wide Angle (UWA) Eyepiece, for beautiful observation sessions with your telescope. This 7-element UWAN eyepiece is ideal for rich-field observations at medium-high power.Extremely good price for its quality: look around and compare! Ideal for fast focal ratio telescopes (Dobsonian, etc.)

Super Wide FOV
Outstanding ultra-wide field of view: 82 deg. F.O.V.
Fully MultiCoated lenses for excellent light transmittance.
Reduced chromatic aberration.
Improved contrast compared to similar EPs.

Great Contrast
Internally fully blackened (lenses edges and internal spacers)
No flaring or ghosting on high-contrast objects.

Light and Easy
Innovative twist-up rubber eyecup.
Long eye-relief: 12mm.
No internal reflections, kidney beaning or other distracting distortions.

Terrific Fit and Finish
High-resistance anodized black barrel.
Smooth design for no hook up in your focuser.
Threaded for use with 1.25" filters.


5.0 (Based on 1 Reviews) 100% of reviewers recommended this product.
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    1. AstroGuy1

      AstroGuy1 New Member

      Skill Level
      Time with Product
      User Notes:
      Review by Joplin of South Carolina.
      Nov 19, 2008

      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.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Apparent Field of View 82°
      Barrel Size 2" (50.8mm)
      Bolt Case Included Discontinued Item
      Bolt Case Size Agena 85x120mm
      Coatings Fully Multi-Coated
      End Caps 2
      Eye Relief by Design 18mm
      Field Stop Diameter 43.5mm
      Filter Threads Standard 2" Filter Thread (M48 x 0.75)
      Focal Length 28mm
      Lens Elements 6
      Lens Groups 4
      Parfocal Yes
      Rubber Eye Guard Yes (Twist-Up Eyecup)
      Blackened Lens Edges Yes
      Manufacturer William Optics
      Eyepiece Focal Length 20.1mm - 30mm
      Eyepiece Field of View Over 80 degrees
      Eyepiece Series William Optics UWAN
      Barrel Type Tapered barrel
      Eyepiece Weight 35.27oz (1,000g)