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William Optics SWAN 72° 40mm Eyepiece - 2"
William Optics SWAN 72° 40mm Eyepiece - 2"
William Optics SWAN 72° 40mm Eyepiece - 2"
William Optics SWAN 72° 40mm Eyepiece - 2"
William Optics SWAN 72° 40mm Eyepiece - 2"
William Optics SWAN 72° 40mm Eyepiece - 2"

William Optics SWAN 72° 40mm Eyepiece - 2"

by William Optics
SKU WO-E-SWA40
$156.00 - $156.00
$156.00
$156.00 - $156.00
$156.00
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  • 40mm Focal Length
  • 72° Apparent Field of View
  • 2" Diameter Barrel
  • 28mm Long Eye Relief
  • Parfocal Design
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics SWAN 72° 40mm Eyepiece - 2"

    The William Optics SWAN 40mm Eyepiece delivers an expansive 72° apparent field of view in a 2" barrel, providing the immersive "spacewalk" experience typically associated with much more expensive designs. With a generous 28mm of eye relief, this eyepiece makes it possible to scan the Milky Way's star fields and frame large nebulae in their entirety, all while maintaining complete viewing comfort.

    A 72° Spacewalk: Rich-Field Views in a 2" Barrel

    Designed as a definitive rich-field eyepiece, the SWAN 40mm transforms your telescope into a wide-angle window on the universe. The 72° apparent field is substantially larger than a standard Plössl, allowing you to fit entire open clusters like the Pleiades (M45) or the sprawling structure of the North American Nebula (NGC 7000) into a single, breathtaking view.

    28mm of Eye Relief: Unmatched Comfort for All Observers

    The SWAN 40mm features an extremely long 28mm of eye relief, a critical specification for comfortable observing sessions. This generous distance allows you to see the entire 72° field without pressing your eye against the lens, making it an ideal choice for observers who wear eyeglasses to correct for astigmatism. You can simply relax and take in the full, unobstructed panorama.

    Contrast-Optimized Design: Fully Blackened Internals for 0 Ghosting

    To ensure the wide field of view is not compromised by stray light, the SWAN 40mm is engineered for maximum contrast. Fully multicoated lenses provide excellent light transmission, while all internal lens edges and spacers are thoroughly blackened. This meticulous attention to detail eliminates internal reflections, preventing ghosting and flaring when observing bright objects like Jupiter or the Moon.

    SWAN 40mm vs. a 40mm Plössl: A Wider Perspective

    While a standard 40mm Plössl is a good low-power eyepiece, its field of view is typically limited to around 43°. The SWAN 40mm eyepiece offers a significant upgrade with its 72° field.

    • Standard 40mm Plössl: Offers a narrow, porthole-like view. It's functional for locating objects but can feel restrictive when observing large star fields.
    • William Optics SWAN 40mm: Delivers a much more immersive, engaging view that feels like you are floating in space. This wider true field makes it easier to find targets and appreciate the context of objects within their stellar neighborhoods.

  • What kind of views does the William Optics SWAN 40mm provide in an f/10 SCT?

    In a typical 8" f/10 Schmidt-Cassegrain Telescope, the SWAN 40mm eyepiece yields 50x magnification and a wide 1.44° true field of view. This is perfect for framing large deep-sky objects like the Andromeda Galaxy (M31) or sweeping through the dense star fields of the Sagittarius Arm of the Milky Way.

    Is the 28mm eye relief on the SWAN 40mm eyepiece good for eyeglass wearers?

    Yes, absolutely. The 28mm of eye relief is exceptionally long, allowing eyeglass wearers to see the entire 72° field of view without removing their glasses. This provides a comfortable, unvignetted viewing experience, which is often not possible with shorter eye relief eyepieces.

    How does the SWAN 40mm's 72° field compare to a standard Plössl eyepiece?

    A standard 40mm Plössl eyepiece typically has an apparent field of view between 40° and 50°. The William Optics SWAN 40mm's 72° field provides a significantly wider, more immersive window into space, making it feel less like looking through a tube and more like a "spacewalk."

    Can I use 2" filters with the William Optics SWAN 40mm eyepiece?

    Yes. The 2" barrel of the SWAN 40mm eyepiece is threaded to accept all standard 2" astronomy filters, such as nebula filters (UHC, O-III) or light pollution filters. This allows you to enhance contrast on faint deep-sky objects while still enjoying the wide-field view.

    Is the William Optics SWAN 40mm eyepiece parfocal?

    Yes, the SWAN 40mm is designed to be parfocal with other eyepieces in the William Optics SWAN series. This means you can switch between them with little to no refocusing required, making your observing sessions more efficient and enjoyable.

    What objects are best for the SWAN 40mm, like the Beehive Cluster (M44)?

    The SWAN 40mm excels at framing large celestial objects. It's ideal for open clusters like the Beehive Cluster (M44) or the Pleiades (M45), large nebulae like the Orion Nebula (M42) in its entirety, and for simply scanning the star-rich regions of the Milky Way.

  • Focal Length 40mm
    Apparent Field of View 72°
    Barrel Size 2"
    Eye Relief 28 mm
    Lens Coatings Fully Multicoated
    Parfocal Yes
    Filter Threads Standard 2" (M48x0.75)
    Internal Baffling Fully Blackened Lens Edges & Spacers
    Eyecup Soft Rubber, Fold-Down

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  • William Optics 2-Year Warranty