ZWO FF90 APO 90mm f/6.8 Refractor Telescope, OTA Only

ZWO FF90 APO
Flat-Field Apochromatic Refractor

Lightweight, compact, and engineered for both immersive visual observing and high-performance astrophotography.

• 90 mm Aperture
• Full-Frame Compatible
• 609 mm Focal Length
• No Field Flattener Required
• Quadruplet Apochromatic Optical Design
• No Specific Back Focus Requirement
• One ED Glass Element
• 360 Degree Camera Rotator
• Dual Finder Scope Mounting System
• 3-inch Rack-and-Pinion Focuser
• Coarse & fine focus adjustment
• 1.25" / 2" Dovetail Plate

Note: Focus can be achieved within a back focus range of 42-73 mm, measured from the M54-M48 interface shoulder

Flexible Connectivity for Multiple Configurations

Astrophotography Cameras
Compatible with ZWO ASI cameras

DSLR & Mirrorless Cameras
Standard camera compatibility

Visual Observation Setup
Supports diagonal and eyepiece

Uniqueness

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.

Convenient Design

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 Degree 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 M48 x0.75 and M54 x0.75 standards. This allows for easy integration with a wide range of imaging accessories.