A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2018 Apr 19, 08:33 -0700
For telephoto lenses over 200mm it is good enough to use the Sun diameter as the yard stick. A high altitude image is best. Then divide minutes of Sun diameter for the date by measured pixels of the diameter. This gives minutes of arc per pixel good through the limited field of view on telephotos. Wide angles are much more difficult. See archives for that problem.
From: Ed Popko
Date: 2018 Apr 19, 03:15 -0700