A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2021 Sep 27, 02:01 -0700
I'm glad I could help.
When you are into the lunars - try to fine-tune your sextant the best you can. The perpendicularity of the index mirror is very important. It is best done not by looking at the arc's limb (the reflection to continue the actual arc) but with two identical diopters - one near the end of the arc, the other - placed so it just appears from behind the index mirror. You look parallel to the sextant's frame and adjust the index's mirror screw to bring diopters' images into perfect coincidence.
Only after that adjustment you may go into IE and side error zeroing.