NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Metal versus plastic or better telescope?
From: Alexandre Eremenko
Date: 2012 Mar 27, 20:15 -0400
From: Alexandre Eremenko
Date: 2012 Mar 27, 20:15 -0400
Lu, You wrote: > Something never discussed is the accuracy achievable -- > even with the best > of sextants -- on the heaving deck of a small craft at sea. In 2005 I posted my results obtained from a 40ft yacht while sailing around England from Kiel. Next year I posted some results obtained from a similar yacht sailing in the Baltic. Of course two 2-week or so trips is not much of experience, but my limited experience agrees with what I read in the literature. Taking a sight from a small boat is very hard, because it is rocking. It is hard to catch a star or Sun, it is hard to keep it in view for few seconds. In many cases I observed without a telescope, as some experienced yachtsmen recommend. In this case the "zero tube" probably helps but I did not have one. Here is a picture: http://www.math.purdue.edu/~eremenko/Navigation/sext.jpg I agree that 0'3 index error (which my SNO permanently has, for years) is totally irrelevant in these conditions:-) And one has to wash the mirrors splashed with salt water after every observation. Alex.