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    Re: Celestial Navigation at NEAF
    From: Paul Dolkas
    Date: 2015 Apr 20, 13:40 -0700

    Mercury is really nice for AHs, but hard to get a hold of these days. The thermometer folks have come up with a non-toxic alternative silver fluid that’s actually an alloy of some low-temp melting metals (-19oC). It’s called Galinstan: wikipedia.org/wiki/Galinstan   It’s fairly corrosive with metals, but since it goes in your mouth (or elsewhere) it has to be fairly benign with your body parts.


    Other than smashing a few hundred thermometers, where you would get a few ounces is beyond me.


    Paul Dolkas


    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Stephen N.G. Davies
    Sent: Monday, April 20, 2015 12:17 PM
    To: paul@dolkas.net
    Subject: [NavList] Re: Celestial Navigation at NEAF


    What was 'obvious' was the need for someone with the relevant knowledge  of what might seem to the uninitiated (like me) a puzzle about the difference between a mirror and a pan of engine oil to clarify why Lt Cmdr John Bingham was right, supposing he was. That has now been provided. Thank you.

    Stephen D


    Sent from my iPhone

    On 20 Apr, 2015, at 9:06 pm, Paul Beckmann <NoReply_Beckmann@fer3.com> wrote:

    Despite initial impressions, the proportion of incident light that is specularly reflected by a particular fluid/air interface is far from "obvious" and is only loosely associated with the overall absorption of light  ("darkness") of the fluid. (See: http://en.wikipedia.org/wiki/Specular_reflection.) For example, highly-polished deep black marble can exhibit a very strong specular reflection. The specular reflection of the celestial body is what we're looking at in an artificial horizon. Used engine oil and molasses *could* do a very fine job of it!


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