[BAA Comets] Azimuth

[Shanklin, Jonathan D.]

When measuring the position angle of a comet tail, north is 0, east 90, south 180 and west 270.  Meteorologically the same convention is used for wind direction.  A compass azimuth has east has 90 and west as 270 (or at least my mapping compass does).  I would suggest giving west as azimuth 270 and east as 90.  I'm not sure where the -90 convention comes from, possibly a mis-interpretation.  The astronomical almanac is quite explicit that azimuth is measured clockwise from north through east.  Geomagnetic declination is measured as +90 or -90, and it may come from this.

Jonathan Shanklin

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