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Gary, 
mind that mercury will freeze at -38�C and you will 
likely encounter lower temperatures on your way to the 
pole. A strong argument for mirror type horizons.
;o)

http://en.wikipedia.org/wiki/File:Pole-observation.jpg
Nansen carried one on his sledge attempt for the pole, 
too.

Wolfgang


Am Mittwoch, 5. Oktober 2011 00:38 schrieb Gary LaPook:
> But many real navigators on sledges and elsewhere
> did carry liquid (including mercury) AHs.
>
> gl
>
> --- On Tue, 10/4/11, Geoffrey Kolbe
>  wrote:
>
> From: Geoffrey Kolbe 
> Subject: [NavList] Re: Home made artificial horizon
> To: NavList@fer3.com
> Date: Tuesday, October 4, 2011, 10:37 AM
>
>
>
> Robert wrote:
>
>
> I can't take it
> anymore!
>
> �
>
> Seems like you folks are going to a great deal of
> hassle and looking in every hidden corner for the
> perfect levelling mechanism and/or to make an
> effective artificial horizon. Short of using a pan
> of motor oil or getting hold of some mercury, the
> best option is, in my opinion, to just go out and
> purchase a Freiberger artificial horizon which comes
> with all you need to obtain pinpoint accuracy (as
> much as is possible with a sextant).
>
>
> No no, you don't understand Robert. There is a
> satisfaction in the process of spending a great deal
> of time and effort to build an AH as cheaply as
> possible using plastic, string and sealing wax. ;-)
>
>
> But on the matter of practicality, I have no doubt
> that you are correct. Could you take the plastic
> string and sealing wax AH to navigate your sledge to
> the middle of the Antarctic? Or your camel to the
> middle of the Sahara desert? Possibly, but people
> have certainly been there and done that with a
> Freiberger AH. I took the short cut many years ago
> and bought one.
>
>
> One note on the use of levels. Just because the
> graduation on the level is only one mil say, (about
> 3 MOA), does not mean that you are limited to an
> accuracy of 1 mil in level adjustment. By turning
> the level end for end for comparison and estimating
> the bubble position to one tenth of a graduation, it
> is possible to get an accuracy in level-ness at
> least an order of magnitude better than the level
> graduations would suggest.
>
>
> Geoffrey Kolbe

   

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