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FrankReedCT@aol.com wrote:

> And let's not forget
> _http://www.analemma.com/_ (http://www.analemma.com/) .
> It's a detailed site on all aspects of the analemma and the equation of
> time, and also one of the oldest amateur web sites on the Internet with really
> good graphic content on a technical subject. It dates back to the late 20th
> century (!).
>

Thanks, Frank, for the reference.  A great site, very well done.

Now, perhaps the historians and/or old timers can help with the
following.

My first exposure to celestial navigation was many years ago as an
undergraduate in applied mathematics. Navigation at sea was disposed of
in perhaps one lecture during a semester course on spherical astronomy
taught by dons who generally looked down on anything of practical use
and certainly never showed us how to use an almanac.

We were taught that right ascension was tabulated and converted to GHA
knowing Greenwich Sidereal Time (GHA Aries):

GHAMS (Mean Sun) + RAMS = GST (GHA Aries).
GHA star + RA star = GST

When I became interested in practical celestial navigation forty years
later right ascension had disappeared from the scene and GMT had almost
disappeared as well.

In some old texts I have noted excerpts from almanacs where for the sun
two quantities R and E were tabulated (together with declination) as a
function of GMT where R was defined as RAMS + 12h
and E was defined as 12h - ET (Equation of Time). So GHAS = GMT + E.

Thus during the period from the early 1900s sun data in the nautical
almanacs seem to have evolved from tabulations of RA, through
tabulations of R and E, to today's tabulations of GHA (or SHA in the
case of stars).

I assume the almanacs have always been subject to fads in the schools
including fads in notation, academic astronomers versus practical
navigators, competition among publishers of almanacs for sales based on
improved ease of use, politics, and so forth. Can anyone share with us
the history of this evolution?

John Cole


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