A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Greg Rudzinski
Date: 2017 Nov 14, 08:15 -0800
I'm not sure of the optical reasons for this but I do notice a benefit from the unsilvered half acting like a whole horizon mirror. If the Sun is filtered to be a little bright to the eye then when it is shifted over to the unsilvered half you will see a dim reflection that can be directly set on the horizon.
From: Peter Monta
Date: 2017 Nov 13, 13:19 -0800