Welcome the brand new ASKAR FRA series! The FRA, which stands for “FLATFIELD REFRACTIVE ASTRAGRAPH”, is a refractive astrograph designed for built-in flat field correction. FRA also used in visual observation, this series creates versatile high-quality flat frame images for astrophotography, is the few great telescope of versatile optical tube.
For easy parameter conversion between different lenses, the first-come of the FRA family features a Petzval-like quintuplet design (two pieces of which are special ED glass) with an aperture of 72mm, a focal length of 400mm and a focal ratio of f/5.6, providing a 44mm image circle.
The FRA400 quintuplet astrograph has adopted modern optical design with a retractable dew shield, a 3″ rack-and-gear-based high-precision reducer containing a 360-degree rotator, M68×1 thread, a 2″ adapter ring and a 1.25″ visual adapter. The reducer is equipped with fine focal adjustment function for more precise calibration in practical observation or sky imaging.
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