Re: Where is Azimuth = 0?
Alan Pickup (alan@wingar.demon.co.uk)
Fri, 18 Apr 1997 18:00:31 +0100
In message <335761AD.12C0@tt-tech.se>, "Bjoern Gimle@tt-tech.se"
<bjorn@tt-tech.se> writes
>Bram Dorreman wrote :
>...
>>But I do understand the coordinates with respect to the local horizon >better
>describe possible brightness changes. If I should report in
>>AltAz (Altitude and Azimuth) I normally add S=0 or N=0.
>
>I believe astronomy text books use S=0, "everybody else" N=0 ?
>...
No, the overwhelming majority of astronomy texts (I've checked a couple
of dozen today) appear to use N=0. One notable exception is Jean Meeus,
the Belgian astronomer who is the guru of computational astronomy and
the author of the book "Astronomical Algorithms". He uses S=0,
supporting this by quoting from a 19th Century text by William Chauvenet
and another by A Danjon in 1959. As I say, I could quote many more
contrary authorities, including the "Explanatory Supplement to the
Astronomical Almanac" which states unequivocally that "Azimuth is
measured in the plane of the horizon from the north, increasing in
positive value towards the east."
I note that N=0 for azimuth is also the convention in Quicksat.
Alan
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