NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Mirrored Artificial Horizon
From: George Huxtable
Date: 2003 Nov 2, 19:04 +0000
From: George Huxtable
Date: 2003 Nov 2, 19:04 +0000
Geoffrey Kolbe wrote- >For those following this particular thread, I will just come back and >defend my analysis of Kieran Kelly's problem, to which George took exception. > >George's analysis is quite correct, as far as it goes, but I think his >analysis is too simplistic. He has taken a very particular scenario for the >topology of the mirror, (which we do not know). When he says he has chosen >dished or spherical shape, he has in fact analysed it as a cylindrical form. No, it was INTENDED to deal with the spherical case and I think it does so. It also covers the case of cylindrical distortion, or its component of curvature along the azimuth in which a sextant altitude is measured. > >I think that if a weighted analysis was done over the possible topologies >of the mirror, it would turn out in the end to be quite similar to the >resolution analysis which I used. I think such an analysis would return a >quite similar result in the order of 0.1 arc-minute for the mean angular >deviation we should expect for a random 2cm diameter section of a mirror >having diameter 14cm and flat to 7 wavelengths. I may be out by a factor of >two or so, but I would be surprised if it was more than that. Geoff and I have looked at this matter from rather different viewpoints and have arrived at rather similar conclusions, and I am happy to shake hands with him about that. >That said, George and I both agree that Kieran should not worry about the >flatness of his mirror. We concur! George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================