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William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73
William Optics Adjustable Reducer Flattener Flat73R for Z73

William Optics Adjustable Reducer Flattener Flat73R for Z73

by William Optics
SKU WO-P-FLAT73R
CA$409.00 - CA$409.00
CA$409.00
CA$409.00 - CA$409.00
CA$409.00
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  • Reduces focal length by a factor of 0.8x
  • Designed for the William Optics Zenithstar 73 telescope
  • Provides edge-to-edge flat field for full-frame sensors
  • Connects via a secure M63 x 1 thread
  • Features a standard M48 x 0.75 camera thread
  • Integrated camera rotator for easy framing
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics Adjustable Reducer Flattener Flat73R for Z73

    The William Optics Adjustable Reducer Flattener Flat73R is engineered specifically to transform the Zenithstar 73 APO refractor into a wide-field astrograph. Its 3-element, 3-group optical design delivers a 0.8x focal reduction, correcting for field curvature across full-frame sensors. The unit attaches via a robust M63 x 1 thread and presents a standard M48 x 0.75 T-mount to your camera, all while weighing just 573.9 g.

    0.8x Focal Reduction: A Wider, Faster Field for the Z73

    The core function of the Flat73R is its 0.8x reduction factor, which shortens the Z73's focal length for a significantly wider true field of view. This allows you to capture large targets like the Andromeda Galaxy (M31) or the entire Veil Nebula complex in a single frame. This reduction also concentrates incoming light, drastically shortening required exposure times and increasing your signal-to-noise ratio on faint deep-sky objects.

    • 3-Element, 3-Group Optics: This sophisticated design ensures high-contrast, sharp stars across the entire image circle, correcting for aberrations introduced by the reduction.
    • Full-Frame Illumination: The optics are designed to fully illuminate and flatten the field for sensors up to full-frame (36x24mm) format, preventing vignetting and distorted stars in the corners of your images.

    Engineered for the Z73: M63 Threads and an 89mm Optical Length

    The Flat73R provides a mechanically rigid connection to the Zenithstar 73. It threads directly onto the focuser's M63 x 1 thread, eliminating any potential for sag or flexure that can occur with compression fittings, especially with the added weight of a filter wheel and camera. The total optical length is 89 mm, composed of the 49 mm flattener body and a 40 mm rotator and adapter assembly that allows for precise framing of your target without loosening the camera.

    • Secure M63 Connection: Ensures perfect optical alignment and stability throughout an imaging session.
    • Standard M48 x 0.75 Camera Thread: Provides a wide, non-vignetting connection compatible with modern DSLR/mirrorless T-rings and dedicated astronomy cameras.
    • Integrated Rotator: The 40 mm adapter section includes a camera rotator, an essential feature for composing your shot without having to unthread your imaging train.

    Z73 Native vs. Reduced: What 0.8x Means for Your Images

    Without a corrector, the Z73 is a superb visual instrument, but for imaging, field curvature will soften stars at the edge of the frame. The Flat73R not only corrects this but fundamentally changes the telescope's imaging characteristics.

    • Wider Field of View: The 0.8x reduction allows you to fit larger celestial objects into your frame compared to imaging at the native focal length. This is critical for large nebulae and nearby galaxies.
    • Faster Imaging: By reducing the focal ratio, the Flat73R gathers the same amount of light in a shorter time. An object that requires a 10-minute exposure at the native focal length can be captured with similar signal in just over 6 minutes, allowing you to gather more data in a single night.
    • Trade-off: The primary trade-off is a slight reduction in image scale. For smaller targets like most galaxies or planetary nebulae, imaging at the native focal length (with a flattener-only accessory) will yield a larger, more detailed image.

  • What does the William Optics Flat73R do for my Z73 telescope?

    The Flat73R is a dual-purpose optical accessory. It acts as a field flattener to correct the natural curvature of the focal plane, ensuring sharp, point-like stars across your entire sensor, especially large full-frame chips. It also acts as a 0.8x focal reducer, which widens your field of view and makes the telescope "faster," reducing your exposure times.

    Is the Flat73R compatible with my full-frame camera?

    Yes. The William Optics Flat73R is designed to provide excellent correction and illumination for camera sensors up to and including the full-frame (36x24mm) format. It provides a standard M48 x 0.75 thread for connection, which is ideal for minimizing vignetting with large sensors.

    How do I attach my camera to the Flat73R reducer?

    You attach your camera via the Flat73R's M48 x 0.75 T-mount thread. You will need an M48 T-ring specific to your camera's mount (e.g., Canon EF, Nikon F, Sony E). This provides a secure, threaded connection for your imaging train.

    Will the Flat73R's weight of 573.9 g affect my Z73's balance?

    Yes, adding the 573.9 g (1.27 lbs) of the reducer, plus your camera and any other accessories, will require you to rebalance your telescope on the mount. The Z73's focuser is robust enough to handle the load, but proper balance in both RA and Dec is critical for accurate tracking.

    Can I frame the entire North American Nebula (NGC 7000) with the Z73 and Flat73R?

    Yes. The wide field of view provided by the 0.8x reduction is ideal for very large targets like the North American Nebula (NGC 7000) and the nearby Pelican Nebula (IC 5070). With most APS-C and full-frame cameras, you should be able to capture the entire nebula complex in a single frame.

    Why would I use the Z73 without the Flat73R reducer?

    While the Flat73R is essential for wide-field imaging, you would remove it for visual observation with an eyepiece. For imaging smaller targets like the Whirlpool Galaxy (M51) or the Ring Nebula (M57), you might prefer to use a 1.0x flattener (sold separately) to maintain the telescope's native focal length for a larger image scale and more detail on the object.

  • Reducer Power 0.8x
    Optical Design 3 Elements in 3 Groups
    Optical Length Flattener 49 mm + Rotator/Adapter 40 mm
    Telescope Connection M63 x 1 (7 mm length)
    Camera Connection M48 x 0.75 (4 mm length)
    Sensor Coverage Full Frame, APS-C, M4/3
    Camera Mount Support Canon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4/3), FUJI X
    Weight 573.9 g / 1.27 lbs
  • William Optics 2-Year Warranty