William Optics 9mm Swan Eyepiece - 1.25"

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William Optics 9mm Swan Eyepiece - 1.25"

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 2ƒ??????????? 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 EPƒ???????????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


Dust Caps IncludedYes
ER10mm to 14mm
Eye Guard IncludedYes
Eye Relief12m
Eyepiece OpticsWide Angle
Field of View72 degrees
Focal Length9mm
FoV 79 Degrees
Free ShippingYes
Lens Elements & Groups5 elements & 4 groups
ManufacturerWilliam Optics
ModelWilliam Optics Swan
Warranty2 Year Warranty
Customer Reviews
4.0 Based on 1 Reviews
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David A.
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.