The Askar FRA600 represents a major evolution in the Flat-Field Refractive Astrograph (FRA) series. With a 108mm aperture, 600mm focal length, and fast f/5.6 focal ratio, it is a dedicated imaging instrument designed to deliver exceptional performance across a massive 66mm image circle, far surpassing standard full-frame requirements.
Built on a sophisticated quintuplet Petzval design, the optical system consists of a front triplet and a rear doublet, incorporating two elements of ED (Extra-low Dispersion) glass. This configuration ensures superior color correction and a naturally flat field, eliminating the need for external flatteners and complex back-focus spacing. Simply reach focus, and your stars are sharp to the edge.
The FRA600 features a massive 4.2-inch rack-and-pinion focuser, robust enough to handle heavy full-frame imaging trains without slipping. It includes a high-precision 1:10 dual-speed adjustment knob and comes with a conical extension adapter set (M90, M54, M48) for versatile camera connections.
Despite its large aperture, the FRA600 remains portable with a retractable dew shield that brings the total length down to just 493mm. The tube rings are multifunctional, offering mounting points on three sides for easy attachment of accessories like guide scopes or control units. It also excels as a high-contrast visual instrument for planetary and deep-sky observation.
For even faster imaging, an optional dedicated reducer is available to bring the focal ratio down to f/3.9, further enhancing its capability as a wide-field light bucket.