A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2016 Dec 17, 10:27 -0800
The double Sun limb to limb observation in the artificial horizon should have the two Suns shaded to match in brightness. I like the images on the dim side. Check focus each time since putting the eye to the scope can change focus slightly. Pre-calculate the PM observations to match AM observations if not using Frank's graphing method. This will save your arm. Expect 1' precision or better from GPS for each individual observation (not average) with artificial horizon if doing everything right using a metal sextant. The average should be better than 1' precision.
You might also try splitting the difference between an upper and lower limb observation. If you wear glasses then try some observations with scope focused with and without glasses on to see what shows best to the eye.