NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Centring Error Detector
From: George Huxtable
Date: 2007 Jan 13, 20:46 -0000
From: George Huxtable
Date: 2007 Jan 13, 20:46 -0000
Phil wrote- | | Here is another model of "calibrator", more recent manufacture : | http://www.hiboox.com/image.php?img=8eb1dd05.jpg | I do not have any information on this instrument. Does anybody knows ? I can try a guess. There seem to be three collimators; going clockwise, in order, call them A,B,C. In this context a collimator is likely nothing more than a straight-filament lamp, at the focal point of a lens, the whole assembly rigidly assembled in a way that allows precise positioning. It produces a broadish beam of parallel light, in a very well-defined direction. The sextant is placed, side on, with its index arm pivot aligned roughly (no call for great precision here, as I see it) with the cenre of the sweep-arc of movable collimator C. A shines into the horizon mirror. B, exactly parallel with A, and looking into the same point as the centre of arc C, provides the index error. And then you just swing C around to whatever scale angle you like, and take the reading of the sextant when the two bright lines, corresponding to A and C, align. Of course, the whole thing depends crucially on exact caliration of the arc that C is mounted on. How that calibration is obtained, I have no idea. The other thing that puzzles me a bit is why B is necessary. Why couldn't that angle, at zero degrees, be catered for by just swinging C into the position that B occupies? Any ideas? Anyone understand it better? George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---