The William Optics RedCat 51 refractor telescope features a 51mm objective lens, in a sleek quadruplet Petzval APO design, using Synthetic Fluoride (FPL53 and FPL51) glass for a full frame flat field image. The optical quality provides a fast focal ratio of f/4.9, 250mm focal length. The William Optics RedCat 51 will out resolve most high resolution DSLR lenses of similar focal lengths with exceptional color and contrast.  The version 3 consists of WIFD internal focusing.

The version 3 of the Redcat 51 consists of WIFD internal focusing. Included with the RedCat 51 is a convenient soft carry case, removeable dew shield, M48 camera adapter, and William Optics patented Bahtinov mask cap. The William Optics RedCat 51 Petzval telescope is ideally suited to night sky astrophotography, wide field astroimaging, and wildlife photography.

True Fluorite is a rare mineral which create very expensive optical lenses. Being a natural material, consistency and impurities are additional factors which further increases cost as does the cost of mining and the impact on our environment. Synthetic fluorite is a highly stable monocrystal completely free of impurities. It does not emit fluorescence in UV light and is an extraordinarily clear lens material. Great care is taken during manufacturing for grinding and polishing this material to ensure that the lens does not chip or scar, and the result is a lens that is completely free of chromatic abberation making it ideal for astrophotography and wildlife imaging or viewing.

• The William Optics RedCat 51 features a 51mm quadruplet Petzval APO design with FPL53 and FPL51 synthetic fluorite glass, ensuring a flat field and exceptional color accuracy for full-frame imaging.
• With a fast f/4.9 focal ratio and 250mm focal length, it delivers sharp, high-resolution images, outperforming most DSLR lenses of similar focal lengths.
• The RedCat 51 V3 introduces WIFD internal focusing, enhancing precision and ease of use.
• Included accessories: soft carry case, removable dew shield, M48 camera adapter, and patented Bahtinov mask cap for precise focus adjustment.
• Ideal for astrophotography, wide-field astroimaging, and wildlife photography, offering premium performance across a range of applications.
• Synthetic fluorite glass eliminates chromatic aberration and is environmentally friendly, ensuring clear, high-quality imaging without impurities or fluorescence.

A major favorable value to the Redcat 51 Version 3 is William Optics patented WIFD internal focusing system. This is preferred for imaging because there is no obstruction that is typically caused with rear focusers that are external. As a result, all the focusing takes place internally inside the optical tube which in addition to having a slicker appearance, reducing vignetting risk and unwanted shifts and jolts which can cause misalignment of the elements

The WIFD RedCat 51 by William Optics is a versatile and feature-packed apochromatic refractor, designed to elevate your astrophotography. Its built-in M48 filter holder allows seamless filter swaps—simply remove the camera adapter, screw in your 2" filter, reattach, and you’re ready to capture stunning images. Whether through its premium optics, robust internal focuser, or the extensive included accessories, this telescope is an essential tool for astrophotographers.

Built with a Petzval design, the RedCat 51 delivers a flat imaging field out of the box, providing sharp stars across a 45mm imaging circle, even with full-frame cameras. With its quadruplet lens system featuring FLP-53 glass, it achieves virtually zero chromatic aberration for superior optical performance. The 51mm aperture, 250mm focal length, and fast f/4.9 focal ratio combine for excellent light-gathering power and reduced integration time, ensuring beautiful wide-field images.

Weighing just 3 lbs (1.77 kg) for the OTA, and 5.25 lbs (2.38 kg) with its included rings and dovetail, the RedCat 51 is highly portable. The package includes thoughtful accessories like a Bahtinov mask dust cover, dew shield, camera angle rotator, Vixen-style dovetail, soft carry case, and a multifunctional saddle handlebar for easy transport and accessory mounting. Compact yet powerful, this refractor pairs perfectly with portable mounts, making it ideal for capturing celestial wonders on the go.