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Prior to 1933, determination of stellar or planetary hour angle involved
the use of siderial time and right ascension. Thereafter, GHA was
tabulated in the NA until the advent of the current style publication, in
which SHA is employed for stars.  Each subsequent "modernization" has
significantly reduced the navigator's work, particularly in the area of
interpolation. Abstracting the relevant almanac data was at one time a
greater chore than the rest of the solution.

The foregoing speaks only to American convention.

Henry

On Mon, 15 Aug 2005 09:41:02 -0400 Robert Eno 
writes:
> I was looking through some old almanacs over the weekend and noted
> that in the 1940's at least, the almanac provided celestial
> coordinates in terms of right ascension, in hours and minutes.
>
> Can anyone tell me at what point in time navigators moved from using
> right ascension to sidereal hour angle for reckoning celestial
> coordinates?  Why was this done?
>
> My first guess is that SHA is easier because one does not have to
> reckon with hours and minutes but instead, uses the more familiar
> degrees and minutes. Nevertheless, this is the system that I learned
> so it would naturally appear to be easier.
>
>
> Robert

   

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