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Subject: Re: Table A4 + elevation?
From: George Huxtable (george@XXX.XXX)
Date: Sat May 03 2003 - 17:08:39 EDT
Marc Bernstein said-
>The sight reduction tables for air navigation do have refraction tables. The
>altitudes are listed in 5000' increments up to 55,000' and there is a
>correction table for non-standard temperatures that goes from +47 to -95 C!
>
>For 2100' and 20C, a little interpolation shows you need to subtract about
>1.5' from Hs
I don't understand this. What is Hs, in this context?
The amount of refraction from a celestial body varies VERY greatly with its
angular altitude in the sky, and so does the additional correction for
height-and-temperature. Marc quotes an interpolated correction of about
1.5', without specifying any angle for the incoming light. Such a large
correction could only apply to a very small apparent angle, of the order of
a couple of degrees, that is, a body just above the horizon, way below what
any self-respecting navigator would choose to observe.
Can Marc explain further, please?
George.
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