William Optics MiniCat 51 WIFD OTA — 51 mm Petzval astrograph The 6-element optical system provides a 178 mm focal length at f/3.5, with a 43.2 mm image circle. Its Petzval design does not require an external field flattener.
Manufacturer model: William Optics MiniCat 51 WIFD OTA · Specifications checked against manufacturer data on 2026-11-03
William Optics MiniCat 51 WIFD OTA — 51 mm Petzval astrograph
The 6-element optical system provides a 178 mm focal length at f/3.5, with a 43.2 mm image circle. Its Petzval design does not require an external field flattener.
Focus and camera alignment
The WIFD rack-and-pinion focuser provides 28 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 supplied adapter does not contain an internal M48 filter thread. Petzval focus depends on the complete camera train remaining within the telescope's focusing range.
Size and mounting
The tube length is 210 mm. OTA weight is 1.67 kg and the manufacturer lists 2.29 kg total weight. The mounting plate is 210 mm Vixen-style / Arca-Swiss dual-sided.
The six-element Petzval system includes two Super ED elements. Its 178 mm focal length and f/3.5 focal ratio suit wide-field imaging of large nebulae and star fields. Field correction is built into the telescope, so a separate flattener is unnecessary.
Compatibility notes
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
84908
Data sheet
Aperture (mm)
51
Camera adapters
Tilt adjuster; camera rotator; M54 to M48 adapter
Camera format
Full frame compatible; APS-C recommended; 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)
178
Focal ratio
3.5
Focuser
WIFD rack-and-pinion
Focuser travel (mm)
28
Focusing mask
Bahtinov mask incorporated in lens cover
Image circle (mm)
43.2
Internal m48 filter thread
No
Lens elements
Six-element Petzval including two Super ED elements
Mounting plate
210 mm Vixen-style / Arca-Swiss dual-sided
Optical design
6-element Petzval
OTA weight (kg)
1.67
Sensor tilt adjustment
Sensor tilt adjuster
Total weight (kg)
2.29
Tube length (mm)
210
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William Optics MiniCat 51 WIFD OTA — 51 mm Petzval astrograph The 6-element optical system provides a 178 mm focal length at f/3.5, with a 43.2 mm image circle. Its Petzval design does not require an external field flattener.
Manufacturer model: William Optics MiniCat 51 WIFD OTA · Specifications checked against manufacturer data on 2026-11-03
