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    Re: Home made artificial horizon
    From: Gary LaPook
    Date: 2011 Oct 5, 13:21 -0700
    Sorry, I did the conversion wrong, it was -30° F, -34° C.


    --- On Wed, 10/5/11, Gary LaPook <garylapook@pacbell.net> wrote:

    From: Gary LaPook <garylapook@pacbell.net>
    Subject: [NavList] Re: Home made artificial horizon
    To: NavList@fer3.com
    Date: Wednesday, October 5, 2011, 1:11 PM

    The coldest temperature I ever encountered was minus 22° C (-30° F) while delivering mail in Chicago a long time ago. Based on this experience, I am fairly certain that I will freeze long before my mercury does.


    --- On Wed, 10/5/11, Wolfgang Hasper <wolfgang.hasper@web.de> wrote:

    From: Wolfgang Hasper <wolfgang.hasper@web.de>
    Subject: [NavList] Re: Home made artificial horizon
    To: NavList@fer3.com
    Date: Wednesday, October 5, 2011, 12:28 PM

    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.

    Nansen carried one on his sledge attempt for the pole,


    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
    > <geoffreykolbe@compuserve.com> wrote:
    > From: Geoffrey Kolbe <geoffreykolbe@compuserve.com>
    > 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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