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William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses
William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses
William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses
William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses

William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses

by William Optics
SKU WO-T-P-181RD
$19,998.00 - $19,998.00
$19,998.00
$19,998.00 - $19,998.00
$19,998.00
Price Match Policy!
  • 181mm Aperture, 998mm Focal Length
  • Fast f/5.5 Focal Ratio
  • 7-Element Optical Design with 3 Super ED Glass Elements
  • 55mm Corrected Image Circle
  • 4.1-inch Rack & Pinion Focuser
  • Integrated Petzval design requires no additional flattener
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • William Optics Pleiades 181 Astrograph f/5.5

    The William Optics Pleiades 181 is a dedicated imaging instrument built around a 7-element optical design that delivers a massive 55mm corrected image circle. Its 181mm objective and fast f/5.5 focal ratio are corrected by three Super ED glass elements, providing a flat, color-pure field across medium format sensors without requiring an external flattener. With a robust 4.1-inch Rack & Pinion focuser and a total weight of 18.7 kg, this astrograph is engineered from the ground up for serious, large-format astrophotography.

    A 7-Element, 181mm Optical System for Flat-Field Imaging

    The Pleiades 181 combines a large 181mm aperture with a 998mm focal length, resulting in a fast f/5.5 system ideal for capturing faint detail in nebulae and galaxies. The optical core is a 7-element Petzval-like design that includes three Super ED glass elements to virtually eliminate chromatic aberration, ensuring stars remain tight, color-neutral points of light.

    Because the field-correcting elements are integrated into the main optical train, the Pleiades 181 produces a natively flat field. This eliminates the need to purchase and correctly space a separate flattener, simplifying your imaging train and guaranteeing optimal correction right out of the box.

    55mm Image Circle for Medium Format Sensors

    Engineered specifically for large-format imaging, the Pleiades 181 illuminates a corrected 55mm image circle. This provides complete, unvignetted coverage for medium format sensors and easily accommodates full-frame, APS-C, and M4/3 cameras with room to spare.

    The expansive corrected field allows you to frame the largest deep-sky objects without compromise and gives you significant flexibility in composing your shots. For imagers using full-frame or smaller sensors, the edge-to-edge correction ensures perfectly round stars across the entire frame, even on the most demanding, high-resolution cameras.

    Engineered for Imaging: 4.1-inch Focuser and Integrated Adapters

    To handle the weight of modern imaging packages, the Pleiades 181 is equipped with a heavy-duty 4.1-inch Rack & Pinion focuser. With 43mm of precise focus travel and native compatibility with popular electronic auto-focusers (EAF), it provides a rigid, repeatable platform for achieving critical focus, even with heavy cameras and filter wheels.

    The astrograph includes a complete set of adapters to streamline camera connection. The package contains M68, M54, and M48 adapters, along with a built-in rotator for framing and a tilt adjuster for perfecting sensor alignment. This comprehensive solution ensures you can connect and optimize your imaging train immediately.

    Robust Mechanical Design: 18.7 kg Total Weight and Ergonomic Handling

    The Pleiades 181 is a substantial instrument, with an optical tube assembly weight of 15 kg (33.07 lbs) and a total equipped weight of 18.7 kg (41.23 lbs). This requires a high-capacity equatorial mount to ensure stability and tracking accuracy. The telescope comes with a standard Losmandy-style dovetail plate for secure mounting.

    To aid in handling and setup, the design incorporates William Optics' signature features, including the innovative Cosmos Steering Wheel for easier lifting and positioning. The tube extends from a retracted length of 1231mm to 1496mm with the dew shield in place, providing excellent stray light and moisture protection for the objective lens.

  • What class of mount is required for the Pleiades 181 astrograph?

    With a total weight of 18.7 kg (41.23 lbs), the Pleiades 181 requires a high-payload equatorial mount. For reliable imaging, a mount with a rated instrument capacity of at least 60-70 lbs (27-32 kg) is strongly recommended to ensure stability and precise tracking with a full camera and guide scope setup.

    Does the William Optics Pleiades 181 require a separate field flattener?

    No. The Pleiades 181 uses an integrated 7-element Petzval-type design where the correcting lenses are part of the main optical assembly. It produces a natively flat 55mm image circle without the need for any additional flattener or reducer.

    How do I connect my camera to the Pleiades 181 focuser?

    The Pleiades 181 includes a comprehensive adapter system to connect most modern astronomy cameras. The package comes with:

    • M68, M54, and M48 Camera Adapters: These three common thread sizes cover the majority of dedicated astronomy cameras and filter wheels.
    • Camera Rotator: Allows for easy framing of your target without loosening the camera.
    • Tilt Adjuster: Enables fine-tuning of the sensor plane to achieve perfect corner-to-corner focus.

    What is the advantage of the Pleiades 181's 55mm image circle for a full-frame camera?

    A full-frame sensor has a diagonal of approximately 43mm. The Pleiades 181's oversized 55mm image circle ensures that the entire sensor is not just illuminated, but fully corrected. This provides excellent star shapes and even brightness from the center to the extreme corners of a full-frame image, preventing vignetting and optical distortions that can appear at the edge of a smaller image circle.

    Can the Pleiades 181 be used for visual astronomy?

    While the Pleiades 181 is optically optimized as an astrograph for imaging, it can be used visually. However, its integrated correcting lenses and focuser design may make it difficult to reach focus with some standard eyepieces and diagonals. Its primary strength and intended application is deep-sky astrophotography.

    How does the Pleiades 181's f/5.5 focal ratio impact imaging the Andromeda Galaxy (M31)?

    The fast f/5.5 focal ratio allows you to collect a significant amount of light in a shorter period compared to slower f/8 or f/10 systems. When imaging a large target like the Andromeda Galaxy (M31), this means you can capture the faint outer spiral arms and dust lanes with shorter individual sub-exposures, improving your signal-to-noise ratio and reducing the demands on your mount's tracking.

  • Lens Type 7-Element Astrograph
    Lens Elements 3x Super ED Glass
    Diameter 181 mm
    Focal Length 998 mm
    Focal Ratio f/5.5
    Image Circle 55 mm
    Focuser 4.1” Rack & Pinion Focuser
    Focuser Travel 43 mm
    EAF Compatible Yes
    Flattener Required No, integrated design
    Supported Camera Formats Medium Format, Full Frame, APS-C, M4/3
    T-Mount Support Canon EF, RF; Nikon F, Z; Sony E; Pentax K; MFT (M4/3); FUJI X
    Dovetail Losmandy Style
    Tube Length (Retracted/Extended) 1231 mm / 1496 mm
    OTA Weight 15 kg / 33.07 lbs
    Total Weight (w/ rings & dovetail) 18.7 kg / 41.23 lbs

    • Pleiades 181 Optical Tube Assembly

      × 1

    • Tilt Adjuster

      × 1

    • Camera Angle Rotator

      × 1

    • M68 Camera Adapter

      × 1

    • M54 Camera Adapter

      × 1

    • M48 Camera Adapter

      × 1

  • William Optics 2-Year Warranty