William Optics 40mm Swan Eyepiece - 2"

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William Optics 40mm Swan Eyepiece - 2"
Item # WO-E-SWA40
  • This William Optics SWAN Eyepiece has a 40mm focal length, 72 field of view and an incredible 28mm of eye relief.
  • Parfocal, to reduce or eliminate focusing when changing magnification.
  • The William Optics SWAN Eyepiece has a black anodized 2" barrel with rubber eyecup, filter threads, and blackened internal threads and lens edges.
  • No flaring or ghosting on high-contrast objects.


William Optics 40mm 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 40mm 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 4-element super-wide angle 40mm SWAN EP’s panoramic views at 72 deg. F.O.V. will leave you speechless!

William Optics 40mm 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 2" filter usage.
  • Rubber grip ring for safe, comfortable handling.
William Optics Product Number: SWAN40
Additional Information

Additional Information

Manufacturer William Optics
Optical Design Wide Angle
Barrel Size 2"
Warranty 2 Year Warranty
Eyepiece Field of View - Apparent 72º
Eyepiece Focal Length 40mm
Eyepiece Eye Relief 28mm
Eyepiece Manufacturer Series William Optics Swan
Eyepiece Weight 1 lb. 4 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 7 item(s)

SWAN 40mm 2''
Es un ocular optimo para focales de F5 en adelante y con calidad buena en la mayor parte del campo. Apenas un 5% puede contener defectos claros en mi F6.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Jose Manuel Garcia Martín / (Posted on 10/30/2012)
wo swan 40mm
Great eyepiece, in combination with my 2 inch WO zenith/prisma (dielectric on my C9,25 it was beautifull to look at the moon and starclusters!
Nice quality for a good price, and the Swan 40mm wel it is very BIG!

Pieter (europe/netherlands
1= Houston, We Have a Problem & 5= It's Out of This World
Review by pieter / (Posted on 1/16/2010)
Outstanding Value
Great value for the money and highly recommend for anyone interested in a quality 40mm, 2in.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Danny / (Posted on 10/27/2009)
Long Time Observer
Of all of the eyepieces that I have ever used, the 40mm SWAN is the best. It's almost like having a completely new telescope. Would I recommend it? Oh yeah!
1= Houston, We Have a Problem & 5= It's Out of This World
Review by / (Posted on 1/13/2009)
This ep gives me 70X with my Celestron CPC-1100, along with a very generous fov. On first light with this ep, it stayed in the scope for most of the night. I found that it was chrisp and clear on all objects. The Wild Duck Cluster (M11 along with numerous globulars of the summer sky were incrediable. M11 nearly filled the ep with an amazing view as did M13 and others. Based on the price, fit and finish and first light performance,it is a very good buy.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Doug - in GA / (Posted on 7/4/2008)
I am somewhat of a novice so please take my opinion with a bit of salt. My standards are likely lower than that of others.

I purchased the SWAN 40mm for a wider field than the Televue Plossls that I am using (The plossls are really nice pieces, too. I really like the WO SWAN 40mm! Of course sharpness distorts a little at the edges. I can live with it.

I looked at M81 and M82 at the same time in the 8 SCT ... that was fun for me and the others at the time. The low magnification and wide field are a pleasure to observe through.

Likely, if I was a very demanding observer I would go with something more expensive. But for my budget and older eyes, this one has a great cost/benefit ratio. I reccommend it for casual wide field viewing. Very nice to use.

1= Houston, We Have a Problem & 5= It's Out of This World
Review by Herb / (Posted on 5/28/2008)
Great Wide Field Eyepiece!
Great Wide Field Eyepiece!

I was making the jump to 2” eyepieces with my Celestron C11 SCT (F/10 and wanted a good quality, long focal length, wide-field eyepiece with as large an AFOV as possible without breaking the bank. I had been happy with my 1.25” William Optics 16mm UWAN (82deg AFOV so I thought I’d give their SWAN line a try. I have been very happy with my purchase and would highly recommend this eyepiece to anyone with the same goals I stated above. The wide 72 degree AFOV gives a wonderful image and I can now fit M81/82 or the Leo Triplet in the same field of view (No small feat in an SCT with a 2800mm focal length. The eye relief of the eyepiece is also just right in that the sweet spot is not too close to the glass, and not too far away either.

At a recent star party I was able to compare my view with a neighboring scope (10” Meade SCT that had the 31mm Nagler (i.e. The Holy Hand Grenade! and I honestly couldn’t tell a major difference between the two views when looking at M81/82. I even preferred the eye relief of my WO 40mm SWAN to the Nagler. I’m not sure how well this sort of comparison would hold up in a fast F/4.5 or F/5 Dobsonian or Newtonian, but it looks beautiful in my F/10 SCT. For the price, this purchase was a no-brainer. Great job William Optics.
1= Houston, We Have a Problem & 5= It's Out of This World
Review by Albuquerque Turkey / (Posted on 5/7/2008)
Included Items

Included Items

  • William Optics Swan 40mm 2" Eyepiece
  • Velvet Protective Bag
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