- Description
- Specifications
The William Optics Ultra-Cat 76 is a high-performance 76mm f/4.8 Petzval astrograph designed for wide-field deep-sky astrophotography. With a 365mm focal length, 5-element advanced Petzval optical system, and 50mm image circle, it is built for sharp flat-field imaging with full-frame, APS-C, and Micro Four Thirds cameras.
Who Is This Product Best For?
Best for astrophotographers who want a compact but serious imaging refractor for nebulae, star fields, large deep-sky targets, travel imaging, and full-frame camera setups.
Why Choose This Product?
- 5-element Petzval optics: Flat imaging field with no separate flattener required.
- 50mm image circle: Supports full-frame, APS-C, and Micro Four Thirds cameras.
- Fast f/4.8 focal ratio: Helps capture deep-sky targets efficiently.
- WIFD focuser: Stable internal focusing with EAF compatibility.
Recommended Uses
- Wide-field deep-sky astrophotography
- Nebula and star-field imaging
- Full-frame astrophotography
- Portable imaging systems
Compatibility and Accessory Notes
The Ultra-Cat 76 includes M54 and M48 camera adapters and supports common camera mount ecosystems including Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, and Fuji X.
Important Limitations
This telescope is designed specifically for astrophotography and does not support visual observation.
Frequently Asked Questions
Does the Ultra-Cat 76 need a flattener?
No. The Petzval optical design provides a flat field without a separate field flattener.
What camera formats work with the Ultra-Cat 76?
It supports full-frame, APS-C, and Micro Four Thirds cameras, with medium-format compatibility noted by William Optics.
Can it be used visually?
No. It is an astrophotography-only telescope.
Our Recommendation
The William Optics Ultra-Cat 76 is a strong choice for astrophotographers who want a premium compact 76mm f/4.8 Petzval astrograph for full-frame wide-field deep-sky imaging. Choose it for nebulae, star fields, and portable imaging rigs. Do not choose it for visual observing.
Optical Diagram Reports
The following optical report graphics are provided for customers reviewing spot diagram, longitudinal aberration, MTF, and relative illumination performance.
| Lens Type | 5-Element Advanced Petzval |
|---|---|
| Lens Elements | Super ED Glass x2, ED Glass x1, Lanthanum Glass x1, X-Element x1 |
| Focal Length | 365 mm |
| Aperture | 76 mm |
| Focal Ratio | f/4.8 |
| Image Circle | 50 mm |
| Focuser | WIFD R&P Focuser; compatible with EAF |
| Focuser Travel | 0-20 mm (ruler to 21 mm) |
| Adapter Included | Sensor Tilt Xterminator Rotator; M54 and M48 camera adapters |
| Optional Flattener | No flattener required |
| T-Mount Support | Canon EF, Canon RF, Nikon F, Nikon Z, Sony E, Pentax K, Micro Four Thirds, Fuji X |
| Camera Format | Full Frame, APS-C, Micro Four Thirds |
| Dovetail Type | Vixen / Arca-Swiss |
| Tube Length | 363 mm - 415 mm |
| OTA Weight | 3.81 kg / 8.4 lbs |
| Total Weight | 4.98 kg / 10.98 lbs |
| Visual Observing | Not supported |
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