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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
$788.00 - $788.00
$788.00
$788.00 - $788.00
$788.00
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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 GT102, FLT132, and GT153 refractors
  • 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 requires 59.5 mm of back focus to achieve pinpoint stars across the entire image frame.

    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 3 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. This corrector is designed exclusively for the Gran Turismo 102 (must have a 3" focuser), the Fluorostar 132, and the Gran Turismo 153. 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: A precise back focus of 59.5 mm from the flattener's shoulder to the camera sensor is required. This distance must be maintained using extension tubes to achieve a flat field.
    • 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 compatible only with the William Optics GT102 (with 3" focuser), FLT132, and GT153. It connects via an M92 x 1 thread.

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

    The required back focus is 59.5 mm. This is the distance from the shoulder of the M48 thread on the flattener to your camera's sensor plane. You must use the correct combination of spacers to achieve this distance for sharp, round stars across the field.

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

    The FLT132 has a native focal ratio of f/6.9. With the 0.8x reducer, the effective focal ratio becomes approximately f/5.5. 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
    Required Back Focus 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

    • William Optics x0.8 Reducer Flattener 7A

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  • William Optics 2-Year Warranty