William Optics RedCat 71 Review by Zane Landers

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.

8.5

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Review

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.

Optics

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71mm (2.8”) Aperture

350mm Focal Length

f/4.9

Petzval Doublet Optics

As with the RedCat 51, the RedCat 71 uses an ED “quadruplet” design – really, a Petzval – with a 2-element objective lens and 2-element field flattener/reducer, each with one extra-low-dispersion (ED) glass element. The Petzval design has less chromatic aberration than a standard, native f/4.9 refractor would and the built-in field flattener is free of the issues of spacing, dust particles, individual product quality, and any potential vignetting issues introduced by a normal external field flattener/reducer, which are often not bundled with many of the imaging refractors that need, or at least benefit from them.

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

Mechanics

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The RedCat 71 focuses with a helical design that works much like a telephoto lens, moving the optics up and down the tube without affecting the placement of your camera sensor or anything else attached to the back. This design keeps dirt, dust, and grit out of the focuser, is immune to sagging, and keeps the center of gravity of your rig pretty much fixed, which helps with avoiding balance issues on your mount’s declination axis. It’s also more familiar if you’re coming from a daylight photography background. The scope’s dew shield retracts and also nicely fits the included Bahtinov focusing mask. Despite the helical focuser, you can easily install a motorized auto focuser on the RedCat 71. There’s also a rotator so you can adjust the tilt of your sensor to optimally fit/frame your chosen target, and a filter drawer to hold a broadband light pollution filter. 

The placement of the RedCat 71’s flattener doesn’t really lend itself well to providing optimal flattening with a filter wheel and monochrome camera – and you may have trouble reaching focus – so the scope works best with color cameras. The back has standard 2”/M48 threads to screw an astronomical camera on directly, or you can purchase a T-adapter nosepiece for your DSLR or mirrorless camera to attach it to the back.

As with the other William Optics refractors, the RedCat 71 has a combination Arca Swiss/Vixen V-style dovetail rail on the bottom, and a carry handle on the top with a slot for any finder or guide scope that uses the standard Synta/Vixen-style finder shoe size; you’re going to want autoguiding with this telescope on almost any mount. 

Mounting Options

While using a small “star tracker” mount with the RedCat 71 is possible, we don’t recommend it. A mount like the Sky-Watcher HEQ5, or larger, with a stated weight capacity of 20 lbs or more and the ability to autoguide, as well as a polar scope, is a must-have. Prepare to spend some money on a guide scope and camera, too. 

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

Not Suitable for Imaging Smaller Targets

High Cost

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.

8.5

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