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ZWO FF131 APO with AM5N Bundle
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FF131 APO Refractor
The ZWO FF131 APO Refractor achieves focus within a back focus range of 42–73 mm. This distance is measured from the M54–M48 interface shoulder.
Main Features
Flexible Connectivity for Multiple Configurations
Uniqueness
Four-Element Optical Design
This telescope features a four-element, fully air-spaced design. These elements deliver a flat imaging field without a flattener.
One ED glass element effectively reduces chromatic aberration. This ensures superior color correction and high image clarity for astrophotographers.
44 mm Image Circle — Full-Frame Support
With a 44 mm image circle, this telescope fully supports full-frame sensors. It accommodates a wide range of advanced imaging setups.
It produces sharp star fields with excellent edge performance. Enjoy consistent quality across the entire frame without vignetting.
Native Flat-Field Design
The native flat-field design eliminates the need for an external flattener. This simplifies your optical train for better results.
Forget complex back focus calculations. Attach your imaging setup and start capturing once focal point is achieved.
Convenient Refractor Design
Coarse & fine focus adjustment
The rigid 3-inch rack-and-pinion focuser provides precise control. It uses a 1:10 dual-speed mechanism for perfect sharpness.
A built-in 360° rotator at the rear allows for smooth camera rotation. This makes framing your celestial targets easy and accurate.
5. Retractable Dew Shield
The telescope features a retractable dew shield. This reduces its length for safer and easier portability during travel.
Precision CNC machining and a high-quality finish ensure durability. Internal coatings minimize stray light to enhance image contrast.
6. Quick-Release Mounting Rings
The mounting rings are fully detachable. This allows for rapid setup or teardown of the telescope while in the field.
Photography Extension Tube
The FF131 APO integrates seamlessly with modern cameras. It includes a four-section extension tube with a 2-inch filter thread.
Rear adapters in M48 and M54 formats are included. This provides flexibility for connecting various astrophotography accessories out of the box.
Performance
Optical Layout
Star Field Map
AM5N Harmonic Drive Mount
The ZWO AM5N Harmonic Equatorial Mount is a next-generation harmonic drive telescope mount designed for serious astrophotography and advanced visual observing. Combining strain wave gear technology, lightweight portability, and high-precision tracking, the AM5N delivers professional-level performance without the bulk of traditional equatorial mounts.
If you're searching for a lightweight equatorial mount with no counterweight required, exceptional tracking accuracy, and full ASCOM compatibility, the ZWO AM5N is one of the most advanced portable mounts available today.
Harmonic Drive (Strain Wave Gear) Technology
The AM5N uses a 300:1 reduction ratio strain wave gear system combined with synchronous belts and precision stepper motors to provide smooth, backlash-free tracking.
Periodic Error: < ±10"
Resolution: 0.17 arcseconds
PE Cycle Duration: 288s
Max Slew Speed: 6°/second
This makes the AM5N ideal for long-exposure deep sky astrophotography, high-resolution planetary imaging.
High Payload Capacity – No Counterweight Needed
Despite weighing only 5.5 kg (12.1 lbs), the ZWO AM5N supports:
15 kg (33 lbs) without counterweight
20 kg (44 lbs) with counterweight
This allows you to mount refractors, astrographs, or compact SCT setups without the complexity of heavy counterweight systems. For portable astrophotographers, this is a major advantage.
Dual Mount Modes: Equatorial & Alt-Az
The ZWO AM5N operates in:
Equatorial Mode (EQ) – optimized for astrophotography
Alt-Az Mode – ideal for visual observing and outreach
Latitude adjustment range: 0° – 90° Azimuth adjustment: ±6°
Compatible with both Losmandy and Vixen dovetail saddles.
Full Connectivity & Smart Integration
The AM5N supports:
ASCOM
LX200 protocol
USB connectivity
Wi-Fi
Bluetooth
ST4 Autoguider Port
Integrated cable management keeps your setup clean and organized.
Built for Extreme Conditions
Operating temperature: -20°C to 40°C
Perfect for winter astrophotography sessions.
⚠ Recommended input voltage: 12V If voltage drops below 10.8V, the mount will emit an under-voltage warning beep. For optimal performance, use the official ZWO power adapter and properly rated power cables.
It is recommended to use a counterweight of ≤5 kg. When using a 5 kg counterweight, the lever arm should be installed within the range of 20 cm to 30 cm.
For counterweights of other masses, the installation position can be calculated as follows:
Assume the counterweight mass is m kg. The allowable lever arm length L is defined by:
10 N·m ≤ m × g × L ≤ 15 N·m
where g = 9.8 m/s², which can be approximated as 10 m/s². For example, if a 2 kg counterweight is used, the allowable range of L is from
10 N·m / (2 × 10 m/s²) = 0.5 m to
15 N·m / (2 × 10 m/s²) = 0.75 m.
Technical Specifications
FF131 APO Refractor
AM5N Mount
Parameter
Specification
Mount type
Harmonic Drive Mount
Mount mode
Equatorial/Alt-Azimuth
Drive
Strain Wave Gear + synchronous belt (300:1 reduction ratio)
Periodic error
< ±10"
PE duration
288s*
Drive (RA)
Stepper motor + synchronous belt + 17 type 100 reduction ratio strain wave gear + brake
Drive (DEC)
Stepper motor + synchronous belt + 17 type 100 reduction ratio strain wave gear
