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
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.
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.
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.
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.
William Optics manufacturer manual
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.
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.
| Recommended camera backspacing | 55 ± 3 mm recommended; Petzval focusing range, not a fixed flattener spacing |
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Data sheet
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
