NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: "Vernier acuity" of horizon IC tests
From: Frank Reed
Date: 2009 Jul 6, 20:19 -0700
From: Frank Reed
Date: 2009 Jul 6, 20:19 -0700
Hi Greg. You should try this without the sight tube. The sight tube serves two purposes: it maintains the collimation of the line of sight so that you are looking along a line of sight parallel to the frame, and by providing a tiny aperture to look through, it generally improves the focus of the eye. We don't need to worry about collimation for IC tests (the error resulting from collimation error goes to zero at zero degrees). The focus of the observer's eye can be equally well improved by wearing eyeglasses. With the sight tube removed, hold the instrument at arm's length. Then you will see the straight line of the horizon on each side of the horizon glass with no "merging" or "fading" zone across the middle. By the way, this possibility of a "hyper-acuity task" only applies to standard style horizon glasses, mirrored on one side, clear on the other, with no dividing line between the sides (just the edge of the silvering itself). -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
