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.
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Stephen N.G. Davies
Sent: Monday, April 20, 2015 12:17 PM
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.
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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