FocalGap

FocalGap helps telescope users understand how an optical setup distributes magnification across available eyepieces. Add a telescope, eyepieces, and an optional Barlow lens to examine the spacing between viewing powers and the effect of different combinations. The app presents a clear visual map of coverage, highlights larger gaps, and supports thoughtful equipment planning before an observing session, whether you are reviewing a familiar setup or considering a new eyepiece.