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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 25, 12:26 -0500
From: Alexandre Eremenko
Date: 2007 Nov 25, 12:26 -0500
Dear George, > Not sure that it was me, though it was a good question. I am about 70% sure this were you, but now that you made the question more precise we can safely refer to it as a "George's question" :-) > by measuring star-star distances or by any other > method, ever discovered reproducible errors, > outside the terms of a > calibration certificate or maker's warranty, In this I failed, even if the second part of this question is omitted, I mean the part beginning with the word "outside". > Karl's new book, "Celestial Navigation in the GPS age", devoted several > pages to helping users to calibrate or check their own sextants that way. He > selected 12 pairs of bright stars Let me recall (I already posted this once on the list that a Russian book proposes a simpler scheme for moderate latitudes of Northern hemisphere. The book lists several distances of selected stars from Polaris. Then for each star, a little supplemental table is provided giving refraction as a function of this star altitude and Polaris altitude (=your latitude). As all altitudes are only needed tith 10 degrees accuracy, the whole set of tables occupoies only two pages. I even wanted to post these tables on the list, but they are made for the epoch of 1960. Anyway, everyone can quickly compute such tables for any epoch. But after many attempts I decided that this method of arc correction does not give the results accurate enough for the Lunar business, unless, perhaps you have a very good 12x telescope. Alex. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---