111F Flat-Field4 1 2" Apo Refractor, Good for Imaging and Visual Description Askar's new 111F quad refractor offers sharp images and versatility at a reasonable price. The 111F's optics cover a full frame imager, without the need for a field flattener. Backfocus distance doesn't need to be precise, making astrophotography simpler with filter drawers, OAGs, and other accessories. The 111F's 766mm focal length gives you a 2. 7 field of view on the long side of your