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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 Ultra Flat 132 (0.79x Reducer)
William Optics Ultra Flat 132 (0.79x Reducer)
William Optics Ultra Flat 132 (0.79x Reducer)
William Optics Ultra Flat 132 (0.79x Reducer)

William Optics Ultra Flat 132 (0.79x Reducer)

by William Optics
SKU WO-P-FLAT-132
$1,068.00 - $1,068.00
$1,068.00
$1,068.00 - $1,068.00
$1,068.00
Price Match Policy!
  • Reduces focal ratio by a factor of 0.79x
  • Provides a flat field for Full Frame, APS-C, and M4/3 sensors
  • 3-element, 3-group optical design
  • Connects to telescope via M92 thread
  • Connects to camera train via M54 thread
  • Weighs 2.42 lbs (1096 g)
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Ultra Flat 132 (0.79x Reducer)

    The Ultra Flat 132 (0.79x Reducer) is the dedicated optical corrector for the William Optics Fluorostar 132, transforming the telescope into a faster, wider astrograph. This corrector provides a 0.79x focal reduction and flattens the image field for sensors up to full-frame format. Its 3-element, 3-group lens design ensures sharp stars across the entire frame, while the robust M92 telescope-side thread and 2.42 lb weight guarantee a rigid, flex-free imaging train.

    0.79x Reduction: Transform Your FLT132 into an f/5.45 Astrograph

    By applying a 0.79x reduction factor, this flattener-reducer converts the FLT132's native f/6.9 focal ratio to a significantly faster f/5.45. This speed increase allows you to capture the same amount of signal in nearly half the time, dramatically improving efficiency during short imaging nights. The corresponding wider field of view lets you frame large celestial targets, such as the Andromeda Galaxy (M31) or the Veil Nebula complex, in a single shot.

    3-Element, 3-Group Design: A Flat Field for Full-Frame Sensors

    Engineered to correct for field curvature, this unit ensures your images have pinpoint stars from the center to the corners of the sensor. The 3-element, 3-group optical formula is optimized to provide a corrected image circle large enough for full-frame cameras, as well as smaller APS-C and M4/3 formats. This eliminates the frustration of elongated stars at the edge of the field, a critical requirement for producing high-quality astrophotographs.

    M92 & M54 Threads: 137.5mm of Precisely Corrected Optical Path

    The Ultra Flat 132 ensures a secure, perfectly aligned connection to your imaging train. It attaches directly to the FLT132 focuser via a male M92 x 1 thread, preventing tilt or sag. The camera side features a standard M54 x 0.75 female thread, providing a solid interface for filter wheels, off-axis guiders, and cameras. For optimal optical correction, the total distance from the reducer's M54 shoulder to the camera sensor must be precisely set, accounting for the unit's 137.5 mm optical length.

    Native f/6.9 vs. Reduced f/5.45: Choosing the Right Focal Length

    Deciding whether to image with the Ultra Flat 132 reducer depends entirely on your target. While the reducer offers significant advantages in speed and field of view, the native focal length of the telescope retains its own utility.

    • Native f/6.9 Imaging: The telescope's native focal length provides higher magnification and resolution. This is ideal for smaller targets like the Whirlpool Galaxy (M51), the Ring Nebula (M57), or planetary details where image scale is more important than field of view.
    • Reduced f/5.45 Imaging: The 0.79x reducer provides a wider field and cuts exposure times nearly in half. This is the clear choice for large emission nebulae like the North American Nebula (NGC 7000) or for creating mosaics of the Milky Way's core.

  • What back focus is required for the Ultra Flat 132 reducer?

    The Ultra Flat 132 reducer has a specified optical length of 137.5 mm. This is the total distance required from the reducer's M54 thread shoulder to the camera sensor for optimal field correction. You must account for the optical path length of any filters, adapters, and the camera's own internal back focus to achieve this precise spacing.

    Is the Ultra Flat 132 compatible with telescopes other than the William Optics Fluorostar 132?

    No. This reducer is optically designed and mechanically threaded specifically for the William Optics Fluorostar 132 telescope. Its M92 x 1 telescope thread and corrective optics are matched to that telescope's specific focal length and optical characteristics. Using it on other telescopes will not produce a corrected image.

    How does the 0.79x reduction of the Ultra Flat 132 affect my exposure times?

    The 0.79x reduction makes the telescope optically faster, reducing the required exposure time for a given signal level. An f/6.9 system becomes f/5.45, which gathers light approximately 1.6 times faster. This means an 8-minute sub-exposure at the native focal length can be achieved in about 5 minutes with the reducer.

    Will the Ultra Flat 132 reducer fully illuminate my full-frame camera?

    Yes. The Ultra Flat 132 is designed to provide a corrected and illuminated image circle that covers Full Frame, APS-C, and M4/3 sensors. You can use it with large-format astronomy cameras or full-frame DSLRs/mirrorless cameras without significant vignetting or distorted stars in the corners.

    How does the Ultra Flat 132 reducer help when imaging the Andromeda Galaxy (M31) with an FLT132?

    The Andromeda Galaxy is a very large target. At the native focal length of the FLT132, you can only capture its bright core. The 0.79x reducer widens the field of view enough to frame the entire galaxy, including its faint outer arms and companion galaxies M32 and M110, in a single shot with a full-frame sensor.

    I'm using an M54 filter wheel with the Ultra Flat 132 reducer. How do I achieve the correct spacing?

    The M54 x 0.75 camera-side thread is your starting point. You need to calculate the total length of your imaging train (filter wheel thickness, camera sensor depth, any off-axis guider) and add M54 spacers as needed to reach the total required 137.5 mm optical length. Remember to account for the 1/3 optical path addition for any glass filters in the light path.

  • Flattener Power 0.79x
    Camera Format Full Frame, APS-C, M4/3
    Lens Design 3 Elements in 3 Groups
    Optical Length 137.5 mm
    Telescope Thread M92 x 1 x 6.5 mm (Male)
    Camera Thread M54 x 0.75 x 4 mm (Female)
    Weight 1096 g / 2.42 lbs

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  • William Optics 2-Year Warranty