Gearbox 0.7x FRA400/500

Askar F3.9 0.7x Full-Frame Reducer for FRA400 – Specifications and Features

The reducer Askar F3.9 0.7x is designed to optimize the performance of the FRA400 astrograph, reducing its original 400mm focal length while lowering the focal ratio for shorter exposures and a wider field of view. This model is perfectly compatible with full-frame sensors, enabling extended image coverage without vignetting and meeting the requirements of most deep-sky astrophotographers.

Askar F3.9 0.7x gearbox specifications

• Focal ratio reduction : The 0.7x reduction factor reduces the focal ratio from f/5.6 to f/3.9, increasing brightness and speed for capturing celestial objects with shorter exposures.
• Reduced focal length : The focal length is shortened to 280 mm, ideal for fast capture and a wide field of view, especially for diffuse objects such as nebulae and star clusters.
• Back focus : The rear focal length is a standard 55 mm, ensuring compatibility with a wide range of accessories and astrophotography cameras.
• Full-frame compatibility : This reducer is optimized for full-frame sensors, offering even coverage and vignetting-free images.

Dimensions and Technical Design

• Outside diameter : 72 mm, offering a robust and stable construction for astrophotography configurations.
• Total length : 63 mm, with a compact design that facilitates mounting on FRA400 systems.
• Front thread : M61*1, providing a stable and secure connection to the FRA400 astrograph.
• Rear thread : M48*0.75, designed to accommodate 2" filters directly, making filter installation quick and easy for users.

Benefits for Astrophotographers

By reducing exposure time and increasing field of view, this reducer is ideal for astrophotographers wishing to capture high-quality deep-sky images. The ability to add 2" filters via the built-in M48*0.75 thread facilitates observations of nebulae and other celestial objects requiring specialized filters.