NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: How far is polaris?
From: Gary LaPook
Date: 2007 Nov 22, 23:01 -0800
From: Gary LaPook
Date: 2007 Nov 22, 23:01 -0800
Gary writes: No, it accounts for the apparant movement of Polaris due to the changing position of the earth's pole. If you look in the Almanac you find that the positions of the stars change during the year. Most of the change of coordinates of the stars published in the almanac are not due to the stars' proper motions but are due to a change in the coordinate system used to define the stars' positions, a coordinate system that changes with the earth's movement. The zero point of the stellar coordinate system is the vernal equinox. Since the earth is precessing and wobbling on its axis this zero point moves along with it making it appear that the stars have moved. Since the earth completes on cycle of precession every 26,000 years, the vernal equinox moves eight tenths of a minute of arc every year and this accounts for most of the changes seen in the stars' coordinates. On Nov 22, 1:39 am, Isonomiawrote: > In other words, A2 accounts for the finite distance of the star! That > is to say, the star wobbles with respect to the background galaxies > (can't say stars because they are too near!!!) > > It is absolutely mind boggling to think that a handheld instrument > like a sextant could possibly be affected by the distance to the > stars. > > It completely turns history on its head. I've always been led to > believe that astronomers looked at the stars as an end in itself - the > great scientists pushing back the frontiers of knowledge - knowledge > for the sake of knowledge's sake! > > In fact, it seems to me that knowledge of the stars and motion of the > planets was a necessary but fairly god-forsaken task mainly undertaken > as a part of the production of accurate navigation tables. > > Engineers produced the equipment necessary to take the measurements, > engineers then took the measurements and then some self-publicist > scientist came along took what was already known by the engineers and > gave it a grand title of the grand theory of space, etc. and claimed > it was entirely his work! --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---