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William Optics x0.8 Reducer Flattener 7A
William Optics x0.8 Reducer Flattener 7A
William Optics x0.8 Reducer Flattener 7A
William Optics x0.8 Reducer Flattener 7A
William Optics x0.8 Reducer Flattener 7A
William Optics x0.8 Reducer Flattener 7A

William Optics x0.8 Reducer Flattener 7A

by William Optics
SKU WO-P-FLAT7A
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$788.00
$788.00 - $788.00
$788.00
$748.60
$748.60 - $748.60
$748.60
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  • Reduces focal ratio by a factor of 0.8x
  • Triplet lens design with 3 elements in 3 groups
  • Corrects field curvature for full-frame sensors
  • Designed for specific William Optics refractors, including the FLT132, FLT156, GT102 and GT153
  • Standard M48 x 0.75 camera connection thread
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics x0.8 Reducer Flattener 7A

    The William Optics x0.8 Reducer Flattener 7A is an essential optical corrector engineered to convert select William Optics refractors into fast, wide-field astrographs. This unit reduces your telescope's focal length by a factor of 0.8x while its 3-element, 3-group triplet lens design delivers a perfectly flat field for full-frame camera sensors. It attaches via a robust M92 x 1 thread and has an optical length of 59.5 mm, with a back focus that depends on the telescope (69.24 mm on the FLT132).

    Triplet APO Optics: 0.8x Reduction for Full-Frame Sensors

    This corrector uses a three-element apochromatic lens structure to achieve its optical goals without introducing chromatic aberration. The 0.8x reduction factor effectively shortens your telescope's focal length, which provides a wider true field of view and reduces exposure times by nearly 40%. The flattener component corrects for the field curvature inherent in refractor optics, ensuring that stars in the corners of your full-frame or APS-C sensor are as sharp as those in the center.

    M92 Connection: Dedicated Fit for Specific William Optics Refractors

    The Flattener 7A is not a universal accessory; it is optically matched to specific William Optics telescopes to ensure optimal correction. It connects directly to the focuser drawtube using a secure M92 x 1 male thread. Back focus settings are available for the Gran Turismo 102 (must have a 3" focuser), Gran Turismo 153, Fluorostar 132, Fluorostar 156, Fluorostar 120 (with back adapter) and Zenithstar 126. This dedicated design guarantees that the flattener's corrective power is perfectly aligned with the optical characteristics of these premium refractors.

    • Camera Interface: The camera side features a standard M48 x 0.75 thread, providing a wide, unvignetted connection for filter wheels, off-axis guiders, and full-frame camera T-rings.
    • Back Focus: The back focus depends on the telescope: 69.24 mm on the FLT132 and 65.3 mm on the FLT156, set with the adjustable back adapter.
    • Weight: At 888.4 g (1.96 lbs), it is a substantial optical element that requires a robust focuser to maintain collimation and prevent sag.

  • Will the William Optics Flattener 7A work with my telescope?

    This flattener is designed for a specific set of telescopes and will not work correctly with others. It is made for the GT102 (with 3" focuser), GT153, FLT132, FLT156, FLT120 (with back adapter) and Zenithstar 126. It connects via an M92 x 1 thread.

    What is the required back focus for the Flattener 7A?

    The required back focus depends on the telescope: 69.24 mm for the FLT132 and 65.3 mm for the FLT156. Set it with the flattener's adjustable back adapter, then fine-tune with test shots.

    How does the 0.8x reduction affect my FLT132's imaging speed?

    The FLT132 has a native focal ratio of f/7.0. With the 0.8x reducer, the effective focal ratio becomes approximately f/5.6. This "faster" system gathers light more quickly, allowing you to capture the same amount of signal on a target like the Heart Nebula (IC 1805) in significantly shorter exposure times.

    Can I use my full-frame camera with the William Optics Flattener 7A?

    Yes, the Flattener 7A is designed to fully illuminate and correct for full-frame sensors (24x36mm format). It also works perfectly with smaller APS-C and M4/3 sensors. The camera connects via a standard M48 x 0.75 T-ring.

    Is the Flattener 7A suitable for imaging the Andromeda Galaxy (M31) with a GT153?

    Absolutely. The GT153 is a long focal length instrument. The 0.8x reduction provided by the Flattener 7A creates a wider field of view, making it much easier to frame large targets like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000) in their entirety.

    What does the "3 Groups 3 Elements" lens type mean for the Flattener 7A?

    This refers to its optical design, which is a Triplet. It uses three individual lens elements arranged in three groups. This sophisticated design allows it to reduce the focal length and flatten the field while maintaining excellent color correction (apochromatic performance), preventing bloated or blue-fringed stars.

  • Flattener Power 0.8x
    Lens Design 3 Elements in 3 Groups (Triplet)
    Supported Camera Formats Full Frame, APS-C, M4/3
    Telescope Connection M92 x 1 x 6.5 mm
    Camera Connection M48 x 0.75 x 4 mm
    Optical Length 59.5 mm
    Supported T-Mounts Canon EF, RF, Nikon F, Z, Sony E, Pentax K, MFT (M4/3), FUJI X
    Weight 888.4 g / 1.96 lbs
    Required back focus 69.24 mm (FLT132), 65.3 mm (FLT156)
    Image circle 44.4 mm
    Designed for FLT120 (with back adapter), FLT132, FLT156, GT102, GT153, ZS126
    Magnification Factor 0.8x

    • William Optics x0.8 Reducer Flattener 7A

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  • William Optics 2-Year Warranty