William Optics Pleiades 181 Astrograph OTA — 181 mm seven-element astrograph The Pleiades 181 has a 998 mm focal length at f/5.5. William Optics specifies a 55 mm image circle.
Manufacturer model: William Optics Pleiades 181 Astrograph OTA · Specifications checked against manufacturer data on 2026-11-03
The Pleiades 181 has a 998 mm focal length at f/5.5. William Optics specifies a 55 mm image circle.
Its seven-element astrograph design needs no separate field flattener.
Rack-and-pinion focusing provides 43 mm travel. Connections: Tilt adjuster; rotator; M48, M54 and M68 camera adapters. The camera adapter provides backfocus adjustment; set the imaging train according to the manual.
Tube length is 1231–1496 mm; OTA weight is 15 kg. Manufacturer total weight is 18.7 kg.
William Optics manufacturer manual
William Optics specifies astrophotography use only; this optical design does not support visual observing. The support parts list specifies a 400 mm Losmandy-style dovetail plate.
The current manufacturer technical table specifies a 4.1-inch rack-and-pinion focuser with 43 mm travel.
Unlike a generic Petzval focus-range assumption, Pleiades spacing must follow the model-specific manual. Do not assume compatibility from sensor diagonal alone.
| Sensor tilt adjuster | Yes |
|---|---|
| Camera angle rotator | Yes |
Data sheet
William Optics Pleiades 181 Astrograph OTA — 181 mm seven-element astrograph The Pleiades 181 has a 998 mm focal length at f/5.5. William Optics specifies a 55 mm image circle.
Manufacturer model: William Optics Pleiades 181 Astrograph OTA · Specifications checked against manufacturer data on 2026-11-03
