Lightweight & Compact - Designed for Both Visual Observation and Astrophotography

*Focus can be achieved within a back focus range of 45-75 mm, measured from the M54-M48 interface shoulder.

Main Features

Flexible Connectivity for Multiple Configurations

Lightweight & Compact
The ZWO FF90 APO features a 90 mm aperture and 609 mm focal length (f/6.8), offering an excellent balance between portability and performance.
The optical tube weighs just 3.92 kg, with a total system weight of 4.52 kg including mounting rings and dovetail plate.
Four-Element Optical Design
The FF90 APO features a four-element, fully air-spaced apochromatic optical design. All four elements work together to deliver a flat imaging field without the need for an additional field flattener.
One ED (extra-low dispersion) glass element is incorporated to effectively reduce chromatic aberration, resulting in improved color correction and image clarity.
44 mm Image Circle - Full-Frame Support
With a 44 mm image circle, the FF90 APO fully supports full-frame sensors and a wide range of imaging setups.
It delivers sharp star fields with excellent edge-to-edge performance, ensuring consistent image quality across the entire frame.
Native Flat-Field Design
The FF90 APO features a native flat-field optical design, eliminating the need for an additional field flattener.
No complex back focus calculations or spacing adjustments are required -- simply attach your imaging setup and start capturing once focus is achieved.

Course & Fine Focus Adjustment
Equipped with a rigid 3-inch rack-and-pinion focuser, the FF90 APO offers precise control with a 1:10 course & fine focus adjustment mechanism.
A built-in 360° rotator at the rear allows for smooth and accurate camera angle adjustments.
Retractable Dew Shield
The FF90 APO features a retractable dew shield, reducing overall length for improved portability.
Precision CNC machining and a high-quality painted finish, combined with an internal anti-reflection coating, help minimize stray light and enhance image contrast.
Quick-Release Mounting Rings
The mounting rings are detachable, allowing for quick and easy setup or teardown of the telescope.
Photography Extension Tube
The FF90 APO includes a photography extension tube with a 2-inch filter thread, along with rear adapters in M48x0.75 and M54x0.75 standards. This allows for easy integration with a wide range of imaging accessories.