NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Calibrating a sextant scale
From: Fred Hebard
Date: 2007 Nov 20, 12:30 -0500
From: Fred Hebard
Date: 2007 Nov 20, 12:30 -0500
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. On Nov 20, 2007, at 11:01 AM, Isonomia wrote: > >> Then calibrate for index error as you already know. If any large >> errors >> are found and corrected for you should repeat the last two steps. >> >> Nicol�s >> >> cal_index_mirror.jpg >> 49KViewDownload > > Nicol�s, thanks - I should have said that I had done the basic > calibration as you suggested. > > The real question I was asking is having done the zero calibration, > how would I check the error at other readings? > > ... the answer must be to take readings between two known stars (not > risking life an limb off a cliff!) which I presume will be very > accurate - but perhaps its not that simple because each will have some > refraction through the atmosphere. > > Has anyone tried this? > > Mike > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---