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    Re: An azimuth nomogram: what's under the hood?
    From: Sean C
    Date: 2018 Mar 12, 22:35 -0700


    Perhaps this will help ...

    From Bowditch, Chapter 17: Azimuths and Amplitudes:

    "A celestial body's amplitude angle is the compliment of its azimuth angle [...] The [amplitude] angle is computed by the formula:

    sin A = sin Dec. / cos Lat.

    This formula gives the angle at the instant the body is on the celestial horizon. The angle is prefixed E if the body is rising and W if it is setting. A body with northerly declination will rise and set North of the prime vertical. Likewise, a body with southerly declination will rise and set South of the prime vertical. Therefore, the angle is suffixed N or S to agree with the name of the body's declination. The Sun is on the celestial horizon when its lower limb is approximately two thirds of a diameter above the visible horizon. The Moon is on the celestial horizon when its upper limb is on the visible horizon. Stars and planets are on the celestial horizon when they are approximately one Sun diameter above the visible horizon."

    Sounds a lot like the diagram you posted. :)


    Sean C.

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