NavList:

Byron, you wrote:
"When the body, sun is rising, it's relative movement is almost zero in horizon motion."

Only in tropical latitudes, of course. At 45 degrees latitude, the motion in azimuth is generally equal to the motion in altitude. So if you select a specific altitude for the amplitude sight (e.g. you have a rule that says "wait til it's half a degree high" while another navigator says "wait til it's 1 SD high") then the difference in altitude will yield a nearly identical difference in azimuth. Of course, a quarter of a degree may not amount to anything worth worrying about. But then there are still higher latitudes...

The above applies only to cases where the traditional amplitude tables are used. If the Sun's altitude is measured, with a sextant or even with a crude device (like an index card held at arm's length), then a proper calculation for azimuth can be done regardless of any details of specific altitude choices or latitudes. Since computation is dirt cheap today, in every sense of the word "cheap", the old amplitude tables really could be set aside (except for emergency use).

-FER

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