Description
Askar provides a brand-new F3.9 full frame reducer for FRA400/FRA500 astrograph, further reducing the focal length and thus shortening the exposure time from the original f/5.6 focal ratio. The reduction factor is 0.7×, and the reduced focal length is 280mm with the FRA400 or 350mm with the FRA500, which can satisfy most deep-sky astrophotography. The back focus is standard 55mm. The reducer has built-in M48×0.75 thread, easy for the attachment of 2" filters.
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