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On 26/03/16 07:03, Frank Reed wrote:
> The plastic Davis Mk 3 sextant is an incredibly basic, yet
> fully-functional, navigation-quality sextant. You could cross oceans
> with one of these things. They look flimsy, distractingly cheap, but as
> proper instruments of reflection they do work, and they are capable of
> measuring altitudes within three or four minutes of arc with just a
> little care in the observation process.

Do you know the Berque twin brothers? They've crossed the Atlantic a
couple of times in self-built small boats, once without any instruments
at all (see e.g. here, in French:
http://www.expemag.com/recit/traversee-de-l-atlantique-en-pirogue.html )

They use this second hand Davis Mk 3, glued to a wooden backboard with a
door handle attached to it. I'm not sure why they did this - increased
inertia maybe? I'll ask them.

On the blog of one of their ocean crossings, they call the Davis Mk 3 'a
marvel of precision', getting to within 0.44 milles of the GPS point,
after averaging 7 sun height observations. In another post they're
pleased with 3 milles. I'm not sure what kind of 'mille' this is.

http://emmanueletmaximilienberque.blogspot.be/2012_01_01_archive.html

Anyway, not an answer to your question at all, but I thought it was fun.

Luc

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