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The new William Optics RedCat 71 is a fast apochromatic quadruplet petzval refractor optimized for widefield astrophotography with a new patented 2-1-1 lens configuration.
With a fast focal ratio of f/4.9 and a focal length of 350mm, the RedCat 71 is perfect for capturing large deep space objects such as the Rosette nebula, the Pleiades, Eta Carina and more. The RedCat also excels as a telephoto wildlife lens.
The unique optical design includes the highest quality FPL-53 synthetic fluorite glass for the best possible colour correction and a flat field across a full-frame sensor with an image circle over 45mm.
The RedCat 71 includes a precision helical focuser that can be locked to maintain focus position. The 2GT standard gear ring is more accurate than those found on typical camera lenses.
Optical design |
Apochromatic petzval (4 elements in 3 groups) |
Objective diameter |
71 mm |
Focal length |
348 mm |
Focal ratio |
f/4.9 |
Image circle |
45 mm |
Material |
Anodized aluminium alloy |
Mount attachment |
210 mm Vixen-style / Arca-Swiss dovetail bar |
Focuser |
Indexed manual helical focuser with 2GT gear ring |
Camera connection |
M48 x 0.75 |
Backfocus |
TBD |
Tube weight |
3.7 kg |
Tube length |
435 mm |
Dew shield diameter |
103 mm |
SKU |
WO-T-C-71RD |
- [A] M48 Dust Cap/Thread
- [B] Tilt Adapter
- [C] Camera Angle Rotator
- [D] Rotator Tension Knob
- [E] Saddle Handlebar (with two M4 thumb screws)
- [F] Helical Focuser with 2GT Gear Ring
- [G] Arca Swiss/Vixen Plate
- [H] Mounting Rings
- [I] Dew Shield with Focus Tension Ring
- [J] Super Bright Bahtinov Mask
- [K] Soft Carry Bag
William Optics has an enviable reputation for producing quality astrographs. This model is a member of this stable with all the image quality you can expect. I've found very nice round stars across the entire photographic field, and I could see no evidence of chromatic aberration. I don't have a full frame camera to try it out with, but expect to have the plaudits this 'scope has acquired confirmed. The helical focuser might put off some rack-and-pinion die-hards but I have found it is quite natural to use - just like a camera lens. I use it with an automatic focuser (ZWO EAF) and a coupling kit (Deep Sky Dad), and this arrangement works exceedingly well. The built-in field rotator is a very welcome feature that has no discernable effect on the focus. Also, there is plenty of back-focus to allow for multiple attachments, like filter wheels and off-axis guiders. I'm looking forward to many years of imaging with this 'scope, and I suspect that any loss of image quality will be down to me, not to the 'scope.
I loved my Redcat 51 so decided to step up in aperture and focal length to the 71. The step is really worth it. Everything I liked about the 51, ease of use, limited peripherals required, ease of set up and a dream to use with a DSLR. A great investment that I am very happy with.
Very happy with it. Nice focal length to suit a number of targets. Flat field so no need for extra bits and pieces. Inbuild adjustments easy to access.