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Step up your astrophotography game with the William Optics RedCat 91, an advanced apochromatic refractor tailored for full-frame and medium-format cameras. This latest addition to the RedCat series combines portability with superior optical performance, making it a versatile tool for capturing breathtaking detail in deep-sky objects.
Highlights:
Petzval Design, No Backfocus Hassles
The 5-element Petzval design eliminates the need for backfocus adjustments, providing sharp, edge-to-edge images with pinpoint stars—ideal for wide-field and detailed astrophotography alike.
Full-Frame & Medium-Format Ready, No Extra Flattener Needed
With a large 55mm image circle, the RedCat 91 is perfect for both full-frame and medium-format cameras. Its advanced optics achieve flat-field images without requiring an additional flattener, giving astrophotographers the freedom to capture expansive views with unparalleled clarity.
Fast f/4.9 Focal Ratio
The RedCat 91's fast f/4.9 focal ratio is designed for bright, vivid captures of galaxies, nebulae, and beyond, ensuring excellent light-gathering power and sharp detail even on faint celestial objects.
Seamless WIFD Focusing
Equipped with William Optics' WIFD focuser, the RedCat 91 provides precise, stable focusing without additional adjustments, enhancing the ease of use for both seasoned astrophotographers and beginners.
The RedCat 91 blends the trusted RedCat heritage with William Optics’ innovative design, making it the ultimate choice for those ready to elevate their night-sky explorations.
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Lens Type
|
5 Elements Advanced Petzval Design |
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Focal Length
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448 mm |
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Diameter
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91 mm |
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Focal Ratio
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f/4.9 |
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Image Circle
|
55mm |
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Focuser
|
WIFD R&P Focuser
|
|
Focuser Travel Length
|
0-36 mm (Ruler to 40mm) |
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Adapter Included
|
Tilt Adjuster
Rotator
M63 → M54 Adapter
M63 → M48 Adapter
|
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Optional Flattener
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No Flattener Required
|
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Camera Format
|
Medium Format (needs additional adapter)
Full Frame
APS-C
M4/3
|
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Total Weight
|
6.3 kg / 13.89 lbs |
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OTA Weight
|
4.72 kg / 10.41 lbs |
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Tube Length
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556 mm |