*Focus can be achieved within a back focus range of 42–73 mm, measured from the M54–M48 interface shoulder.
Main Features
Flexible Connectivity for Multiple Configurations
Uniqueness
1. Four-Element Optical Design
The FF131 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.
2. 44 mm Image Circle — Full-Frame Support
With a 44 mm image circle, the FF131 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.
3. Native Flat-Field Design
The FF131 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
4. Coarse & fine focus adjustment
Equipped with a rigid 3-inch rack-and-pinion focuser, the FF131 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.
5. Retractable Dew Shield
The FF131 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.
6. Quick-Release Mounting Rings
The mounting rings are detachable, allowing for quick and easy setup or teardown of the telescope.
Photography Extension Tube
The FF131 APO is designed for seamless integration with modern imaging systems, and includes a standard four-section photographic extension tube with a 2-inch filter thread. Rear adapters in both M48x0.75 and M54x0.75 formats are also included, making it easy to connect a wide range of cameras, filters, and astrophotography accessories for a clean, flexible setup right out of the box.
Performance
Optical Layout
Star Field Map
Product Diagram
Specifications
| Product Name | FF131 APO |
| Effective Aperture | 131mm |
| Focal Length | 983mm |
| Focal Ratio | f/7.5 |
| Objective Type | Four-element air-spaced APO(including one ED element) |
| Image Circle | 44mm |
| Maximum Rear Connection Length (Focuser Retracted) | |
| Imaging Mode | 73 mm (measured from the M48×0.75 male thread) 91 mm (measured from the M54×0.75 male thread) |
| Observation Mode | 131 mm (measured from the 1.25" interface) 142 mm (measured from the 2" interface) |
| Minimum Rear Connection Length (Focuser Retracted) | |
| Imaging Mode | 42 mm (measured from M48×0.75 male thread) 60 mm (measured from M54×0.75 male thread) |
| Observation Mode | 100 mm (measured from 1.25" interface) 111 mm (measured from 2" interface) |
| Overall Length | 878 mm (with 1.25" interface retracted) 941 mm (with photography extension tube retracted) 963 mm (with 1.25" interface dew shield extended) 1026 mm (with photography extension tube dew shield extended) |
| Telescope Body Weight | 7.9 kg |
| Standard Configuration Weight | 9.4 kg (including handle, mounting rings, and dovetail plate) |
| Rear Interfaces | M78 x 1- 55mm Extension Adapter M78 x 1 - M54 x 0.75 M54 x 0.75 - M54 x 0.75 M54×0.75 - M48×0.75 (built-in M48×0.75 filter thread) |
What's in the box?
FF Series Telescope Comparison
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