William Optics Apochromatic Refractor 76mm f/4,8 - AP 76/365 UltraCat WIFD

William Optics Apochromatic Refractor AP 76/365 UltraCat WIFD

With a 5-element advanced Petzval optical design, including super ED and lanthanum glass, and a fast f/4.8 focal ratio, this telescope delivers stunningly sharp, flat-field images across its 50 mm image circle. Optimized for full frame, APS-C, and M4/3 sensors, it also offers compatibility with medium format cameras for outstanding wide-field astrophotography.

The UltraCat astrograph at a glance

Advanced 5-Element Petzval Optics: Eliminates field curvature, ensuring sharp, edge-to-edge stars without additional flatteners.

50 mm Large Image Circle: Fully supports Full Frame cameras, APS-C and M4/3 sensors for optimal performance. Compatible with Medium Format.

Fast f/4.8 Optics: Superior light-gathering capability, enabling deep-sky imaging with shorter exposure times.

WIFD (William Internal Focuser Design): Patented internal rack-and-pinion focuser ensures stable and precise focusing. No vignetting or balance issues - ideal for astrophotography. Compatible with EAF (Electronic Automatic Focuser) for precision focus control.

Sensor Tilt Xterminator (STX) & Rotator: Integrated tilt adjuster eliminates sensor misalignment, ensuring uniform image sharpness.

No Flattener Required: The optical design naturally corrects field curvature, simplifying setup.

Anti-Shrink Lens Cell Technology: Reduces thermal expansion effects, maintaining perfect optical alignment in any climate.

Patented Bahtinov Mask for Focusing: Built-in focusing aid ensures pinpoint star sharpness with ease.

Premium Build & Ergonomic Design: Lightweight yet robust construction with a sleek anodized finish.

Patented handle bar design for enhanced portability and ease of use.

Versatile Camera Compatibility: Supports Canon EF, RF, Nikon F,Z, Sony E, Pentax K, MFT, and FUJI X mounts.

No Flattener Required
The Petzval optical design naturally corrects field curvature, simplifying setup.

Anti-Shrink Lens Cell Technology
Reduces thermal expansion effects, maintaining perfect optical alignment in any climate.

Patented Bahtinov Mask for Focusing
Built-in focusing aid ensures pinpoint star sharpness with ease.

Sensor Tilt Xterminator (STX) & Rotator
Integrated tilt adjuster eliminates sensor misalignment, ensuring uniform image sharpness.

Superb focusing
The William Optics Internal Focus Design (WIFD) is an innovative and revolutionary design that combines a precise (patented) internal focusing mechanism with the highest quality optics available, offering the ultimate apochromatic refractor for astrophotography. Designed from the ground up to handle even the largest, heaviest, cooled cameras, this optics is uncompromising in its quality. The focuser movement is integrated into the main tube, so no adjustments are visible from the outside.

The user can enjoy the benefits of a conventional focuser with two fine focus controls without having to worry about the limitations normally found with conventional rear-mounted focusers (vignetting). The integrated position indicator window on the focuser allows instant verification of the graduated numerical display.

The focus is compatible with ZWO´s EAF.

- Telescope
- Camera adapters
- Dust cap with Bahtinov mask
- Tube rings
- Handle bar with integrates finder base
- Dovetail bar
- Bag

Sample images provided by the manufacturer

William Optics has published an image field comparison and some sample images. The images below are clickable:

The overview clearly shows the image area for sensors with different formats (visual image circle: approx. 7.8°).



The large North America Nebula, measuring 120´x140´, fits nicely into the field of view.



Even the larger Cepheus Nebula, measuring 170´x140´, can be nicely captured.



The Sagittarius Cloud is also quite large, measuring approximately 120´x60´.

Safety informations: PDF Download