RedCat 91: the classic red version of the Cat 91
The William Optics RedCat 91 WIFD brings the Cat 91 optics in the classic red RedCat version. The Petzval design with FPL53 and FPL51 glass provides a color-pure, sharp image across the entire field, up to full-frame size. Suitable for astrophotography and nature photography.


Fast optics, solid base
With f/4.9 and a 448mm focal length, you capture a lot of light: short exposures, less noise, and more detail in medium-sized nebulae and galaxies. The M48 and M54 camera adapters directly connect common camera trains, and the internal WIFD focuser maintains constant balance. The Bahtinov mask is located in the lens cap.
In the box
- Optical tube Cat 91/448 with WIFD focuser
- M48 and M54 Camera Adapters
- Dovetail pliers
- Integrated Bahtinov mask in the lens cap
- Nylon tote bag
Featured accessories
A William Optics UniGuide 50mm Guidescope (from 189 euros) is the fitting guide for this class. The M48 and M54 connectors directly accept common William Optics camera adapters.
For whom yes, for whom no
For: astrophotographers who want the Cat 91 optics in the recognizable red finish, with a complete basic setup. Not for: those who want a rotator and tilt adapter as standard; the BlackCat 91 WIFD includes those for the same price.
Specifications
| Optical design | Apochromat, Petzval (FPL53 and FPL51) |
| Opening | 91 millimeters |
| Focal length | 448 mm |
| Opening ratio | f/4,9 |
| Focuser | WIFD (intern) |
| Camera connection | M48 and M54 |
| Field of view | Flat to full-frame |
| Execution | OTA (loose tube) |
Unsure about the right tube for your camera and mount? The telescope selection aid helps you choose. Also view all Refracting telescopes and the full range of William Optics.





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