William Optics RedCat 91 WIFD

Name: William Optics RedCat 91 WIFD
Brand: William Optics

William Optics

William Optics RedCat 91 WIFD is a 91 mm Petzval APO refractor for wide-to-mid-field nebulae and general deep-sky imaging.

telescope premium

Best Current Offer

Cloud Break Optics

In stock

$2,858.00

Other retailers

High Point Scientific (In stock)
$2,858.00
Mile High Astronomy (In stock)
$2,998.00

Specifications

Optics

Optical design: Petzval APO refractor
Aperture: 91 mm
Focal length: 448 mm
Focal ratio: f/4.9
Dawes limit: 1.27"
Glass / elements: Petzval APO objective

Imaging

Image circle: 55 mm
Camera format: Full frame / APS-C / Micro 4/3
Full-frame coverage: Yes
Back focus: No flattener required
Corrected field: Native flat imaging field

Specifications

Weight: 10.41 lb (4.72 kg)

Mechanical

Focuser: WIFD rack-and-pinion internal focuser

Astrophotography Fit

Best for wide-to-mid-field nebulae and general deep-sky imaging when the mount, camera format, and correction hardware are chosen as one system.

William Optics RedCat 91 WIFD sits in the telescope slot for wide-to-mid-field nebulae and general deep-sky imaging. The useful headline specs are aperture 91 mm, focal length 448 mm, f/4.9.

Camera coverage: Full frame / APS-C / Micro 4/3. Image circle: 55 mm. Back focus: No flattener required.

Fast astrographs collect signal quickly, but they are unforgiving: collimation, tilt, filter behavior, and back-focus spacing show up immediately in star shapes.

Best paired with

Rigid focuser, tilt adjuster, and exact corrector spacing
Cooled cameras with a sensor inside the corrected image circle
High-throughput filters that behave well at fast focal ratios

Not recommended for

Users who do not want to tune collimation, tilt, and spacing
Thick or narrow filters that show strong bandpass shift at fast focal ratios
Loose camera adapters or focusers that cannot hold the imaging train square

Where To Buy

Some links on this page are affiliate links. Prices and availability are pulled automatically from each retailer and updated daily.

Retailer	Price	Availability	View Offer
Cloud Break Optics Cloud Break Optics	$2,858.00	In stock Updated 9/19/2026	View Offer - $2,858.00
High Point Scientific High Point Scientific	$2,858.00	In stock Updated 9/20/2026	View Offer - $2,858.00
Mile High Astronomy Mile High Astronomy	$2,998.00	In stock Updated 9/20/2026	View Offer - $2,998.00

Price History

Chronological retailer pricing with out-of-stock points shown at reduced opacity.

Cloud Break Optics High Point Scientific Mile High Astronomy