William Optics UltraCat 76 WIFD f/4.8 Astrograph

A 76mm full-frame astrograph for wide nebula fields with real aperture

The William Optics UltraCat 76 (also written Ultra-Cat 76) is a 76mm f/4.8 apochromatic astrograph built for deep-sky imaging with full-frame, APS-C and Micro Four Thirds cameras. Its 5-element advanced Petzval design (2 Super ED, 1 ED, 1 lanthanum and 1 special X-element) delivers a flat 50mm image circle with no separate flattener. The 365mm focal length is a sweet spot for large nebulae and galaxies: it frames the whole Andromeda Galaxy on APS-C while showing more detail than a 250mm scope.

Why imagers choose the UltraCat 76

• Edge-to-edge stars on full frame: the 5-element design keeps stars round and tight to the edge of the 50mm image circle.
• No flattener to buy or space: the flattening is built in. Set your camera at the recommended 55mm (±3mm) of back focus.
• Fast f/4.8 optics with 76mm of aperture: nearly twice the light-gathering area of a 56mm scope at the same focal ratio.
• WIFD internal focuser: a rack-and-pinion focuser that moves the optics inside the sealed tube, so your camera never shifts or sags. The knob removes to fit an electronic autofocuser.
• Sensor Tilt Xterminator and rotator: fix sensor tilt from the side and frame targets without removing the camera.
• Anti-shrink lens cell: designed to hold optical alignment through large temperature swings, a real help on Colorado nights.
• Built-in Bahtinov mask: the lens cap doubles as a focusing mask.

Field of view with popular cameras

With an APS-C camera, the Andromeda Galaxy, the Rosette Nebula, the California Nebula or the Orion Nebula with the Running Man fit comfortably in one frame. Full frame takes in the Heart Nebula or the whole North America and Pelican Nebulae.

What you'll need to complete your setup

• A mount: at 10.98 lbs with its ring, handle and dovetail, the UltraCat 76 pairs well with a strain-wave mount like the ZWO AM5N or Sky-Watcher Wave 100i.
• A camera: a cooled astronomy camera such as the ZWO ASI2600MC Pro or ASI2600MM Pro, or a DSLR or mirrorless camera. Use the included M48 adapter with a wide M48 T-ring for your camera, such as the Canon EF, Canon RF, Nikon F, Nikon Z or Sony E T-mounts.
• Autofocus (optional): the WIFD focuser accepts an electronic focuser such as the ZWO EAFN or EAF Pro.
• Guiding (optional): the handle bar's mini Vixen base takes a UniGuide 32 or UniGuide 50 guide scope.

Compare the William Optics Cat astrographs

Why buy from Mile High Astronomy

• No surprise import duties: our price includes all import duties. Telescopes ordered directly from overseas are often listed without duties, which are then billed separately before delivery.
• Ships from the US: your UltraCat 76 ships from our Denver store, not from overseas.
• Expert help from astrophotographers: we can help you choose a mount, camera and focuser for your setup, and we're here to help after the sale.

What's in the box

• William Optics UltraCat 76 WIFD f/4.8 astrograph with Sensor Tilt Xterminator and camera angle rotator
• Bahtinov mask cap for precise focusing
• M48 and M54 camera adapters, with adapter wrench
• Mounting ring and handle bar with mini Vixen base
• 210mm dual Vixen / Arca-Swiss dovetail plate
• Riser blocks
• Soft carry case
• Allen key set

UltraCat 76 FAQ

Do I need a field flattener?

No. The 5-element Petzval design has the flattening built in. Set your camera sensor 55mm (±3mm) behind the telescope using the included adapters and the right T-ring or spacers.

UltraCat 76 or UltraCat 56?

The UltraCat 56 is lighter and frames about a third wider, ideal for travel and the largest targets. The UltraCat 76 gathers 84% more light and its 365mm focal length shows more detail in galaxies and nebulae, but it needs a mount that can carry about 11 lbs plus your camera.

UltraCat 76 or Cat 91?

The Cat 91 has more aperture, a longer 448mm focal length and a 55mm image circle that covers medium format sensors with an extra adapter. The UltraCat 76 is about 3 lbs lighter and frames wider fields.

What mount do I need?

Plan for about 11 lbs for the telescope with its ring, handle and dovetail, plus your camera, filter wheel and guiding gear. A strain-wave mount like the ZWO AM5N or a mid-size German equatorial mount is a good match.

Can I add an electronic focuser?

Yes. The focus knob removes so an electronic focuser like the ZWO EAFN can drive the WIFD focuser with a flexible coupling. Installation steps are in the online manual.

Optical performance

Specifications

Online manual: back focus, tilt adjustment, electronic focuser installation and mounting.