RedCat 71 Review

Introduction

Like the smaller RedCat 51, the William Optics RedCat 71 is a high-quality imaging refractor that combines the best aspects of telephoto lenses and traditional astronomical refracting telescopes into a high-quality, well-arranged, and easy-to-use package. The RedCat 71 is a little more expensive and demands more work to use than the smaller RedCat 51, but is still a great telescope for those starting out in astronomical imaging. The RedCat 71 has an even larger image circle than the 51mm model at 48mm and works with almost any color astronomical camera, mirrorless camera, or DSLR. It needs no external field flattener and accepts a wide variety of accessories to improve your imaging experience.

Optical Design & Imaging Performance

As with the RedCat 51, the RedCat 71 uses an ED “quadruplet” design—technically a Petzval—with a 2-element objective lens and a 2-element field flattener/reducer, each containing one extra-low-dispersion (ED) glass element. Compared to a standard native f/4.9 refractor, this design exhibits less chromatic aberration. The built-in field flattener also avoids the usual pitfalls of external flatteners: spacing sensitivity, dust contamination, unit-to-unit variation, and potential vignetting—issues common in many imaging refractors that require (or strongly benefit from) a separate flattener.

The RedCat 71 illuminates a 48 mm image circle, large enough for nearly any astronomical CMOS camera (such as those from ZWO) or a full-frame DSLR/mirrorless sensor. As long as your camera is color, it should pair very well with the RedCat 71. Focusing with the helical focuser is straightforward, and the field of view remains flat all the way to the very edges of the frame.

Mechanics

The RedCat 71 uses a helical focusing system that behaves much like a telephoto lens, moving the optics up and down the tube without shifting the position of your camera sensor or anything attached at the back. This keeps dirt and grit out of the focuser, eliminates sag, and maintains a nearly fixed center of gravity—helpful for avoiding balance issues on your mount’s declination axis. It’s also immediately familiar if you come from a daytime photography background.

The dew shield retracts and neatly stores the included Bahtinov focusing mask. Despite the helical design, you can still install a motorized autofocus system. There is also a built-in rotator for framing your target and a filter drawer for a broadband light-pollution filter.

The placement of the internal flattener doesn’t lend itself well to optimal use with a filter wheel and monochrome camera—you may struggle to reach focus—so the scope works best with color cameras. The rear of the scope offers standard 2″/M48 threads for direct attachment of an astronomical camera, or you can use a T-adapter nosepiece for DSLR or mirrorless bodies.

As with other William Optics refractors, the RedCat 71 features a combined Arca-Swiss/Vixen-style dovetail rail on the bottom and a carry handle on top with a standard Synta/Vixen finder shoe. You will almost certainly want to autoguide with this telescope on most mounts.

Mounting Options

While it is technically possible to use the RedCat 71 on a small “star tracker” mount, it’s not recommended. A mount in the class of the Sky-Watcher HEQ5 or larger—with a stated payload capacity of at least 20 lbs, autoguiding support, and a polar scope—is effectively a requirement. Plan on investing in a guide scope and guide camera as well.

What can you see if you look through it?

While it’s an imaging telescope primarily, the RedCat 71 can be used with 1.25” eyepieces provided you buy the separately-sold 1.25” screw-on diagonal. However, compared to a regular doublet with a 2” focuser and 2” diagonal your field of view is restricted, and twisting to focus while looking through the telescope isn’t the most intuitive. There are cheaper, larger, and arguably better refractors for visual use around the same aperture (some of which also work for imaging).

The phases of Mercury and Venus, craters on the Moon, rings of Saturn, cloud belts on Jupiter, and a dark spot or two on Mars are visible, along with the tiny dots that are the ice giant planets, but a cheap 70mm achromatic refractor is probably a better planetary scope and almost any Dobsonian or catadioptric will win on aperture alone. Deep-sky views of open star clusters and the largest nebulae are pleasing under dark skies, but 71mm isn’t a lot of aperture; 50–60mm binoculars have more light-gathering ability, a wider field of view, and a fraction of the cost. With light-polluted skies, you won’t be seeing much. And, simply put, the RedCat 71 is terribly cost-ineffective for visual astronomy in every capacity.

Drawbacks

Due to its short focal length, the RedCat 71 is of course not suitable for imaging smaller targets like galaxies and globular star clusters; however, many of the telescopes suited for such tasks are not the kind you want to be starting out with.

The high cost of the RedCat 71 is a bigger concern. A 72mm doublet and flattener from another manufacturer such as Apertura, with the same provided kit including the handle, costs only about half the price of the RedCat 71. Sure, the RedCat has a nicer fit and finish, but is it really worth the price hike? When you consider the difficulties of using the RedCat as part of a monochrome imaging setup with a filter wheel, the value proposition is even worse. The RedCat is arguably easier to use and equip, but in exchange for making the beginning of your astrophotography journey easier, it eats into your future budget and makes upgrades harder. The choice is yours.

Conclusion

The William Optics RedCat 71 is a nice telescope for astrophotography and a good choice for beginners, but you should consider your options, budget, and goals carefully before choosing it.