William Optics RedCat 51 II APO 250mm f/4.9

William Optics RedCat 51 Gen 2 Refracting Telescope

The second-generation William Optics 51mm RedCat refractor helps amateur astronomers find pinpoint stars, perfect color correction, and zero chromatic aberrations in your astrophotos and through your eyepiece. The 51 mm RedCat is a perfect scope for those beginner and advanced astrophotographers looking to shoot expansive deep-sky photos and increase the portability of their astrophotography setup. Upgraded from the previous RedCat 51mm, this Gen 2 RedCat scope comes with a smaller extended length, from 12" (305 mm) to 11" (280 mm), and the Focus Tension Ring has been changed from black to an aesthetically please red to match the rest of the RedCat body.

This RedCat refractor has a 51 mm objective lens, a 250 mm focal length, and a fast f/4.9 focal ratio. With the help of the Ohara FPL53 glass, full-frame camera sensors will see perfectly round stars to the very edges of their fields of view. The RedCat 51 comes with 48 mm threads, so it is compatible with several different brands of digital and mirrorless cameras such as Canon, Nikon, Sony, Pentax, as well as the most popular dedicated astronomy camera manufacturers on the market today like ZWO and QHY. The RedCat 51II also comes with a camera sensor tilt adjuster to help you get those great images.

The William Optics RedCat 51 Telescope optics are made from Ohara FPL53 synthetic fluorite glass for high contrast and extremely sharp results when used in both visual and photographic applications. The Petzval design, which consists of four elements in three groups, also known as a Quad, produces a full-frame flat field, with an image circle of >43 mm (full-frame). With the APO performance, this telescope has virtually zero chromatic aberration.

RedCat 51II Body Design and Included Features

The RedCat 51 Gen 2 body is made of a strong aluminum alloy and is anodized in a beautiful red color for strength and durability. A matching dew/sun shield can be attached when needed and then inverted to store the lens without the additional length the dew shield provides. An aluminum threaded cap protects the optics whenever the William Optics RedCat is not in use.

The dew shield of the WYO 51 mm RedCat is reversible. In order to increase the portability of this refracting telescope, the dew shield can be place backward on the telescope, shortening the length by about 82 mm.

In the center of the RedCat 51II refractor body, there is a ring mount that attaches to the reversible base and wraps securely around the body of the lens. A red anodized knob allows you to loosen the ring enough to fully rotate the RedCat 51 body, and of course, it is also used to lock the ring in place. The “ring” has a flat section that has two 1/4-20 holes spaced far enough to allow the addition of a red dot finder, microphone, or other compatible accessories.

William Optics has completed this design with a sturdy Cat mounting ring. This ring can hold both the optical tube and a large-sized DSLR without any noticeable flexure. William Optics has designed the Cat ring to be modular, meaning you can also add a finder scope or guide camera (not included). The single-tube Cat mounting ring attaches to the included 210 mm dual Arca-swiss/Vixen-style dovetail. With the dovetail, you to use this scope with both an equatorial mount and a photographic tripod!

The integrated Bahtinov mask now offers you the ability to achieve precise focus across the entire imaging circle without the need for a motorized focuser!

Calibrated Helical Focuser with Field Rotator

The helical focuser with a focusing index on the RedCat 51 has a focus tension ring that allows you to lock focus or just increase or decrease the drag to your liking. Included is a field rotator is included and is laser etched with a degree indicator. With this feature, inspired by luxury watches, you can rotate you camera to fit within a degree of accuracy, and mosaics of large celestial objects or sections of the sky will be much easier!

A filter slot is built into the OTA just after the rotator and accepts 48 mm filters, and the back of the RedCat 51 telescope is fitted with M48 threads. Attach a full-frame (M48) M 4/3, Nikon, Canon, Sony, or Pentax T-ring to the threads and use your DSLR to produce beautiful images.