William Optics 9mm Swan Eyepiece - 1.25"

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William Optics 9mm Swan Eyepiece - 1.25"
Item # WO-E-SWA09
  • This William Optics SWAN Eyepiece has a 9mm focal length, 72 field of view and an excellent 12mm of eye relief.
  • Parfocal, to reduce or eliminate focusing when changing magnification.
  • The William Optics SWAN Eyepiece has a black anodized 1.25" barrel with rubber eyecup, filter threads, and blackened internal threads and lens edges.
  • No flaring or ghosting on high-contrast objects.


William Optics 9mm SWAN Eyepiece

The Swan eyepieces are super wide angle designs with 72° apparent field of view. They use simple but sophisticated five-lens optical systems for generally higher contrast than the more complicated optical designs used in some other super wide angle eyepieces that use up to eight lenses. All lenses are fully multicoated for high light transmission. Lens edges and internal field stops are blackened to reduce internal reflections and improve contrast. The eyepiece rubber grip ring is useful for safer handling of the heavier 2” eyepieces in cold weather when wearing gloves. The eyepieces have soft roll down rubber eyecups for eyeglass use. They can be used for all types of observing, both day and night!

The William Optics SWAN 9mm Eyepiece has soft roll down rubber eyecups for eyeglass use. They can be used for all types of observing, with all telescope types, but they are recommended for use with focal ratios up to f/6 and above. Dust caps are provided for both ends of each eyepiece. A soft protective drawstring-equipped velvet storage bag is standard equipment with each.

This 5-element super-wide angle 9mm SWAN EP’s panoramic views at 72 deg. F.O.V. will leave you speechless!

William Optics 9mm SWAN Eyepiece Features

  • Fully Multicoated lenses for excellent transmittance..
  • Reduced chromatic aberration.
  • Improved sharpness and contrast throughout the field.
  • No internal reflections, kidney beaning, pin-cushion or other distortions.
  • Smooth design for no hook up in your focuser.
  • Threaded for filter usage.
  • Rubber grip ring for safe, comfortable handling.
William Optics Product Number: SWAN9
Additional Information

Additional Information

Manufacturer William Optics
Optical Design Wide Angle
Barrel Size 1.25"
Warranty 2 Year Warranty
Eyepiece Field of View - Apparent 72
Eyepiece Focal Length 9mm
Eyepiece Eye Relief 12mm
Eyepiece Manufacturer Series William Optics Swan
Eyepiece Weight 2.5 oz.
Field Stop Not supplied by manufacturer
Number of Lens Elements & Groups 5 elements, 4 groups
Special Feature None
Comes with Dust Caps? Yes
Comes with Eye Guard? Yes

Customer Reviews 1 item(s)

Mini-Space portal
This is an interesting eyepiece, that I would say is a mini portal to space, much like the Naglers portal to space, where the SWAN is 72° and the Nagler is 82°. I gave it 4 stars because the eye relief is the limiting factor. You need to put your eye pretty close to the eyepiece in order to get a fairly good view. You do need to move your eye around to get the full effect of the mini-portal effect. There is minimal pin cushion at the edge of the field. I would put the good field of view at about 3/4 and the outer 1/4 is a tiny bit blurry, with noticeable astigmatism, but not enough to totally degrade the viewing experience. I notice that when viewing the planets, it is a comfortable field of view but when viewing the Sun, I do notice that my eye needs to be closer to the eyepiece to get a good view. All in all, I like this eyepiece and the field of views is pretty amazing.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by David Aucoin / (Posted on 3/30/2012)
Included Items

Included Items

  • William Optics Swan 9mm Eyepiece
  • Velvet Pouch
Questions & Answers

Product Questions

9mm Swan EP ,Thinking about more eyepieces for my Binoviewer & looking at the review on this eyepiece ; the eyepiece was liked , but the 12mm eye relief could have been better , hard to look through ; That said I now wonder how they would preform in my William Optic Binoviewer using them as a set ?
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