A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2021 Jan 23, 18:16 -0800
Here's how I do it.
Leave the center screw for the prism loose so that you have enough motion to disengage the teeth from the threads on the shaft. Set.the altitude to zero. Go outside and looking around the side of the sextant and also through the prism you can line up the star as observed directly along the side with the image as seen in the prism. Wiggle the prism to take the teeth out of engagement and move it with your fingers until the two images are lined up. Then tighten down the screw.