NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Bauer's book, was Re: Newton and Halley
From: Frank Reed
Date: 2007 Dec 03, 00:24 -0500
From: Frank Reed
Date: 2007 Dec 03, 00:24 -0500
Alex, you wrote: "Let me recall that Bauer's book contains several misleading statements and this is not only about history. This was discussed on the old list several years ago, when I just joined the list. I tried to test my new sextant with the star distances following Bauer's recommendations. As the list members immediately pointed to me these recommendations contain a substantial gap: he gives a table of distances, specially for sextant testing, but fails to mention that one has to correct for refraction. Refraction distorts star distances substantially, even if two stars have the same altitude." Well, not quite. He does indeed describe how to correct for refraction for stars in a vertical line. He also says that when stars are at the same altitude "refraction can be ignored" and that's not true, though the effects are usually smaller then. In this case, he was only repeating an error which was also present in venerable Bowditch at that time. And that's the case with most of the small errors in this book. They were common errors for most books on navigation written 20-30 years ago. They weren't his errors personally. Incidentally, except for rather gross checks on angles, the biggest problem with that table (and also the one in Letcher's book from a few years earlier) is that it ignores aberration which changes the star-star distances by as much as 0.6 minutes of arc during the course of the year. Of course, as you noted in another post, all of this is unimportant today since computation is dramatically cheaper today than it was back then and we can easily do the correct calculation when needed. The small mis-statement that most bothers me in Bauer is his recommendation that one should only shoot "mid-altitude bodies" because of the difficulty of swinging the arc at relatively low or relatively high altitudes. This is a misconception, but once again, it was an overwhelmingly common misconception at that period of time. -FER --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---