ZWO FF90 APO Flat-Field Apochromatic Refractor

Article number:	ZWO FF90-APO
Availability:	More on the Way to us
Delivery time:	More on the Way to Us

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

Uniqueness

1. 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.

2. 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.

3. 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.

4. 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.

Convenient Design

5. Coarse & fine focus adjustment

Equipped with a rigid 3-inch rack-and-pinion focuser, the FF90 APO offers precise control with a 1:10 coarse & fine focus adjustment mechanism.
A built-in 360° rotator at the rear allows for smooth and accurate camera angle adjustments.

6. 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.

7. Quick-Release Mounting Rings

The mounting rings are detachable, allowing for quick and easy setup or teardown of the telescope.

8. Photography Extension Tube

The FF90 APO includes a photography extension tube with a 2-inch filter thread, along with rear adapters in M48×0.75 and M54×0.75 standards.
This allows for easy integration with a wide range of imaging accessories.

Performance

Optical Layout

Star Field Map

Product Diagram

Specifications

Product Name	FF90 APO
Effective Aperture	90mm
Focal Length	609mm
Focal Ratio	f/6.8
Objective Type	Four-element air-spaced APO (includes 1 ED element)
Image Circle	44mm
Maximum Rear Connection Length (Focuser Retracted)
Imaging Mode	75 mm (measured from M48×0.75 male thread) 93 mm (measured from M54×0.75 male thread)
Observation Mode	112 mm (measured from 1.25″ eyepiece holder) 122 mm (measured from 2″ eyepiece holder)
Overall Length	513 mm (with 1.25″ interface retracted) 550 mm (with photography extension tube retracted) 599 mm (with 1.25″ interface extended) 636 mm (with photography extension tube extended)
Telescope Body Weight	3.92 kg
Standard Configuration Weight	4.52 kg (including handle, mounting rings, and dovetail plate)
Rear Interfaces	M64×1-M54×0.75 M54×0.75-M54×0.75 M54×0.75-M48×0.75 (built-in M48×0.75 filter thread)

What’s in the box?

FF Series Telescope Comparison