NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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!
--Paul
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