Skip to content
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61
William Optics Adjustable Flat61 for Z61

William Optics Adjustable Flat61 for Z61

by William Optics
SKU WO-P-FLAT61A
$278.00 - $278.00
$278.00
$278.00 - $278.00
$278.00
Price Match Policy!
  • 1.0x Flattener Power
  • Designed for William Optics Zenithstar 61
  • Full-Frame Sensor Coverage
  • Adjustable Back Focus Mechanism
  • M54 Telescope Thread & M48 Camera Thread
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics Adjustable Flat61 for Z61

    The William Optics Adjustable Flat61 is the definitive imaging accessory for the Zenithstar 61, delivering edge-to-edge pinpoint stars on sensors up to full-frame format at a native 1.0x power. Its 2-element, 2-group optical design corrects the field curvature inherent in a fast refractor, connecting to the telescope via a rigid M54 x 0.75 thread and to your camera with a standard M48 x 0.75 T-mount. Weighing just 272.8 g, the unit's optical path consists of the 39.5 mm flattener body and a 19 mm rotator and adapter section, engineered for precise spacing and image composition.

    1.0x Power for Full-Frame Correction with the Zenithstar 61

    This flattener corrects field curvature without altering the native focal length or focal ratio of your Z61 telescope. The 1.0x magnification ensures the field of view you framed visually is the same one you capture, preserving the telescope's original optical characteristics. The 2-element in 2-group lens design is optimized specifically for the Z61's optics, providing a flat, corrected image circle large enough to accommodate full-frame (36x24mm) sensors without vignetting or distorted stars at the corners.

    M54 Telescope Connection & M48 Camera Interface

    The Flat61A attaches to the Z61 focuser using a robust M54 x 0.75 threaded connection, eliminating any potential for tilt or flex that can occur with simple compression fittings. The camera side features the astrophotography standard M48 x 0.75 thread, providing a wide, secure aperture for filters and direct connection to dedicated astronomy cameras and a broad range of DSLR/mirrorless T-mounts. The integrated rotator allows you to frame your target perfectly without loosening any threaded connections, maintaining rigid alignment throughout your imaging session.

    Adjustable Back Focus for Edge-to-Edge Sharpness

    Achieving a perfectly flat field requires precise spacing between the flattener's rear element and the camera sensor. While fixed-length flatteners work well with a specific camera setup, the Adjustable Flat61 acknowledges that filter wheels, off-axis guiders, or different T-ring thicknesses can alter this critical distance. This unit's key feature is its ability to be fine-tuned, allowing you to dial in the exact back focus required by your unique imaging train to guarantee sharp stars across the entire frame, not just in the center.

  • What is the purpose of the William Optics Adjustable Flat61?

    The Flat61A is an optical corrector designed specifically for the William Optics Zenithstar 61 refractor. It flattens the curved focal plane of the telescope, ensuring that stars are sharp and pinpoint across the entire field of view, from the center to the corners of your camera sensor.

    How do I connect the Flat61A to my Z61 and camera?

    The flattener connects directly to the Z61 focuser's drawtube via a secure M54 x 0.75 thread. The camera side features a standard M48 x 0.75 thread, which is compatible with most dedicated astronomy cameras, filter wheels, and T-mounts for DSLR and mirrorless cameras.

    Why is an adjustable flattener like the Flat61A better than a fixed one?

    An adjustable flattener provides the flexibility to achieve perfect back focus with various imaging setups. Different cameras, filter thicknesses, and adapters can slightly change the ideal spacing. The Flat61A allows you to fine-tune this distance, ensuring optimal optical correction regardless of the specific components in your imaging train.

    Does the Flat61A change the focal length of my Zenithstar 61?

    No. The William Optics Flat61A is a 1.0x flattener, meaning it does not reduce or extend the telescope's focal length. It corrects for optical aberrations while preserving the Z61's native field of view and f-ratio.

    Can I use the William Optics Flat61A with a full-frame camera like the Sony A7 series on my Z61?

    Yes. The Flat61A is explicitly designed to provide a corrected image circle for Full Frame sensors. With the appropriate M48 T-mount for Sony E-mount cameras (listed in the supported T-mounts), you can achieve a flat field with your Sony A7 series camera.

    Will the Flat61A provide a flat field for imaging the Andromeda Galaxy (M31) with my Z61 and an APS-C camera?

    Absolutely. The flattener is designed for sensors up to full-frame, so it will provide excellent correction for smaller APS-C and M4/3 sensors. It will ensure that all the stars across the vast expanse of the Andromeda Galaxy (M31) are rendered as sharp points.

  • Flattener Power 1.0x
    Optical Design 2 Elements in 2 Groups
    Camera Format Support Full Frame, APS-C, M4/3
    Telescope Connection M54 x 0.75 x 5 mm
    Camera Connection M48 x 0.75 x 4 mm
    Optical Path Components Flattener 39.5 mm + Rotator/Adapter 19 mm
    Supported T-Mounts Canon EF, RF; Nikon F, Z; Sony E; Pentax K; MFT (M4/3); FUJI X
    Weight 272.8 g (0.60 lbs)
  • William Optics 2-Year Warranty