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| author | Joseph Hunkeler <jhunkeler@gmail.com> | 2015-07-08 20:46:52 -0400 |
|---|---|---|
| committer | Joseph Hunkeler <jhunkeler@gmail.com> | 2015-07-08 20:46:52 -0400 |
| commit | fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4 (patch) | |
| tree | bdda434976bc09c864f2e4fa6f16ba1952b1e555 /noao/obsutil/src/pairmass/airmass.x | |
| download | iraf-linux-fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4.tar.gz | |
Initial commit
Diffstat (limited to 'noao/obsutil/src/pairmass/airmass.x')
| -rw-r--r-- | noao/obsutil/src/pairmass/airmass.x | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/noao/obsutil/src/pairmass/airmass.x b/noao/obsutil/src/pairmass/airmass.x new file mode 100644 index 00000000..8e9c585d --- /dev/null +++ b/noao/obsutil/src/pairmass/airmass.x @@ -0,0 +1,23 @@ +include <math.h> + +# AIRMASS -- Compute airmass from DEC, LATITUDE and HA + +# Airmass formulation from Allen "Astrophysical Quantities" 1973 p.125,133. +# and John Ball's book on Algorithms for the HP-45 + +double procedure airmass (ha, dec, lat) + +double ha, dec, lat, cos_zd, x + +define SCALE 750.0d0 # Atmospheric scale height + +begin + if (IS_INDEFD (ha) || IS_INDEFD (dec) || IS_INDEFD (lat)) + call error (1, "Can't determine airmass") + + cos_zd = sin(DEGTORAD(lat)) * sin(DEGTORAD(dec)) + + cos(DEGTORAD(lat)) * cos(DEGTORAD(dec)) * cos(DEGTORAD(ha*15.)) + x = SCALE * cos_zd + + return (sqrt (x**2 + 2*SCALE + 1) - x) +end |