NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calibrating a sextant scale
From: Alexandre Eremenko
Date: 2007 Nov 22, 10:46 -0500
From: Alexandre Eremenko
Date: 2007 Nov 22, 10:46 -0500
Dear Bill, 1. I am very interested in the results of your testing, especially for SNO-T. Do you have a factory certificate of this sextant to compare? 2. If I understand your first procedure correctly, a collimator creates a beam of parallel light rays. (As you say, it is "focused at infinity"). You measure the angle between these two beams with a theodolite, and then with a sextant. Now, how wide is this beam for a typical collimator? I mean, if you place your collimators only few meters away from the theodolite, how large is the space from which both these beams from the collimators are visible? If I understand correctly you then replace the theodolite by a sextant; the sextant has to be roughly on the same place where the theodolite was. But the typical distance between the two mirrors of the sextant is few centimeters. Will you be able to catch the beams from both collimators into the sextant mirrors? In other words, how wide are these beams? Another problem I see with this setting is that even the smallest LED light is not a point source at the distance of few meters. Alex. As I understand from the journal description of the arrangement in the Kew observatory, the collimators there are of very large diameter, and the distance to them is not few meters but something like 15 meters. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---