SpaceCat 51 III
William Optics
From ~$1,102.42
2 stores
In stock
The SpaceCat 51 III is a compact 51mm Petzval apochromatic refractor featuring William Optics' patented WIFD (Internal Focus Design) for seamless autofocus compatibility with the ZWO EAF and electronic focusers. With a 250mm focal length and f/4.9 focal ratio, it delivers razor-sharp, flat-field imaging ideal for wide-field astrophotography and deep-sky surveys. Built with premium FPL-53 synthetic fluorite glass in a 4-element design, this scope eliminates chromatic aberration and requires no external field flattener, making it an excellent choice for both amateur astronomers and professional astrophotographers using full-frame or APS-C cameras.
Specifications
| Focal ratio | f/4.9 |
| EAF Compatible | ✓ |
| Close Focusing Distance | 3.7 m |
| Focal length | 250 mm |
| Focuser Type | WIFD (Internal Focus Design) |
| Field Flattener Required | false |
| Glass Type | FPL-53 |
| OTA Weight | 1.77 lb |
| Optical design | Petzval (4-element) |
| Tube Length | 298 mm |
| Focus Travel | 23 mm |
| Aperture | 51 mm |
| Image Circle | 48 mm |
| Total Weight with Accessories | 2.38 kg |