William Optics RedCat 51 WIFD — 51 mm Petzval astrograph The 4-element optical system provides a 250 mm focal length at f/4.9, with a 48 mm image circle. Its Petzval design does not require an external field flattener.
Manufacturer model: William Optics RedCat 51 WIFD · Specifications checked against manufacturer data on 2026-11-03
William Optics RedCat 51 WIFD — 51 mm Petzval astrograph
The 4-element optical system provides a 250 mm focal length at f/4.9, with a 48 mm image circle. Its Petzval design does not require an external field flattener.
Focus and camera alignment
The WIFD rack-and-pinion focuser provides 23 mm travel and 1:10 fine adjustment. A camera rotator controls framing, while a sensor tilt adjuster allows sensor alignment. The lens cover incorporates a Bahtinov focusing mask.
Imaging connections
Tilt adjuster; camera rotator; M54 to M48 adapter. The M48 adapter incorporates an internal filter thread. Petzval focus depends on the complete camera train remaining within the telescope's focusing range.
Size and mounting
The tube length is 298 mm. OTA weight is 1.77 kg and the manufacturer lists 2.38 kg total weight. William Optics lists a 210 mm dual-sided Vixen-style / Arca-Swiss mounting plate in its model support documentation.
Petzval focus range must accommodate the complete imaging train; do not interpret recommended camera spacing as an exact flattener backfocus. Confirm supplied adapters and revision.
Additional specifications
Recommended camera backspacing
55 ± 3 mm recommended; Petzval focusing range, not a fixed flattener spacing
82930
Data sheet
Aperture (mm)
51
Camera adapters
Tilt adjuster; camera rotator; M54 to M48 adapter
Camera format
Full frame, APS-C and Micro Four Thirds
Camera rotation
Camera angle rotator
Electronic focus
ZWO EAF compatible; use the manufacturer installation guide for the selected EAF model.
External field flattener required
No
Fine focus ratio
1:10
Focal length (mm)
250
Focal ratio
4.9
Focuser
WIFD rack-and-pinion
Focuser travel (mm)
23
Focusing mask
Bahtinov mask incorporated in lens cover
Image circle (mm)
48
Internal m48 filter thread
Yes
Mounting plate
210 mm dual-sided Vixen / Arca-Swiss
Optical design
4-element Petzval
OTA weight (kg)
1.77
Sensor tilt adjustment
Sensor tilt adjuster
Total weight (kg)
2.38
Tube length (mm)
298
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William Optics RedCat 51 WIFD — 51 mm Petzval astrograph The 4-element optical system provides a 250 mm focal length at f/4.9, with a 48 mm image circle. Its Petzval design does not require an external field flattener.
Manufacturer model: William Optics RedCat 51 WIFD · Specifications checked against manufacturer data on 2026-11-03
