William Optics RedCat 51 II APO Refractor
The ultimate portable companion for wide-field astrophotography.
The RedCat 51 II is a legendary 51mm Petzval refractor designed for photographers and astronomers who demand high-quality optics in a compact form. With its fast f/4.9 focal ratio and 250mm focal length, it captures stunning deep-sky wide-field images with ease.
Key Highlights:
- Built-in Bahtinov Mask: The patented lens cap design includes a Bahtinov mask for quick, razor-sharp focusing.
- Full-Frame Coverage: A massive 43mm+ image circle ensures pinpoint stars to the corners of your full-frame sensor.
- Versatile Mounting: Dual-sided dovetail (Vixen and Arca-Swiss) for easy attachment to both star trackers and photo tripods.
- Premium Engineering: Features a calibrated Helical focuser with tension adjustment and a built-in field flattener.
"Designed for those who want to take their astrophotography studio anywhere."
| Focal Length | 250mm |
| Aperture (Diameter) | 51mm |
| Focal Ratio | f/4.9 |
| Optical Design | Petzval (4 elements in 3 groups) |
| Image Circle | >43mm (Full Frame) |
| Focuser | Calibrated Helical Focuser |
| Tube Length (Min/Max) | 228mm (Inward) / 291mm (Outward) |
| Dew Shield Diameter | 80mm |
| Adapters Included | M48 (Compatible with M48 filters) |
| Weight (OTA only) | 1.3kg (2.87 lbs) |
| Total Weight (with ring & dovetail) | 1.76kg (3.87 lbs) |
| Brand | William Optics |