NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calibrating a sextant scale
From: Paul Hirose
Date: 2007 Nov 20, 12:03 -0800
From: Paul Hirose
Date: 2007 Nov 20, 12:03 -0800
Fred Hebard wrote: > Yes, for star-to-star distances, you have to correct for spherical > aberration when clearing the observed distance, just like the moon. > It's been tried. The problem is getting a precise star-to-star > distances. I don't believe anybody claims to have solved that > problem. The only solution seems to be to take it to somebody who > has a calibrating machine, or roll your own if you have access to > tens or hundreds of thousands of dollars of optical equipment. The subject of star separation angles has been discussed on the list, so I'm sure several programs exist to compute accurate values. Here's a quick and dirty one that I wrote: http://home.earthlink.net/~s543t-24dst/sofajpl/star2star.html The whole package is free, but it's no good unless you have a Windows machine and a C or C++ compiler. And there's no user interface to speak of. To change input values you have to edit the source code and recompile. However, the program is pretty thorough. It corrects for effects such as proper motion, aberration (not spherical aberration -- that's something else), and refraction. In the example, refraction decreases the Deneb - Vega separation angle by 30 seconds of arc. -- I block messages that contain attachments or HTML. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---