ZWO FF90 APO — 90 mm flat-field refractor A 609 mm, f/6.8 optical tube for astrophotography and visual observing. Its four air-spaced elements include ED glass for colour correction. The native flat field covers a 44 mm image circle without a separate flattener.
Manufacturer model: ZWO FF90 90/609 APO Refractor OTA · Specifications checked against manufacturer data on 2026-11-03
A 609 mm, f/6.8 optical tube for astrophotography and visual observing. Its four air-spaced elements include ED glass for colour correction. The native flat field covers a 44 mm image circle without a separate flattener.
The 3-inch rack-and-pinion focuser has 1:10 fine adjustment. A 360° rear rotator sets camera orientation. ZWO specifies an imaging focus range of 45–75 mm from M54–M48 shoulder; this is a usable focusing range, rather than a fixed reducer-spacing requirement.
M48 × 0.75 and M54 × 0.75 interfaces accommodate imaging trains. The photographic extension accepts a 2-inch threaded filter. Eyepiece interfaces support visual use.
A retractable dew shield shortens the tube for transport. Detachable rings support mounting. Body weight is 3.92 kg; the standard configuration with handle, rings and dovetail weighs 4.52 kg.
ZWO FF90 manufacturer specifications
These specifications describe the telescope component only. Native flat field design does not require an added flattener; the imaging train must still fit the available focus travel and interface. Package mount/tripod specifications are not inferred from telescope data.
| Focuser size inches | 3 |
|---|---|
| Camera rotator degrees | 360 |
| Mounting rings | Detachable |
| Length visual retracted (mm) | 513 |
| Length imaging retracted (mm) | 550 |
| Length visual extended (mm) | 599 |
| Length imaging extended (mm) | 636 |
Data sheet
ZWO FF90 APO — 90 mm flat-field refractor A 609 mm, f/6.8 optical tube for astrophotography and visual observing. Its four air-spaced elements include ED glass for colour correction. The native flat field covers a 44 mm image circle without a separate flattener.
Manufacturer model: ZWO FF90 90/609 APO Refractor OTA · Specifications checked against manufacturer data on 2026-11-03
