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include <math.h>
# The sun's velocity with respect to the local standard of rest is:
define RAVSUN 18. # RA of sun's velocity
define DECVSUN 30. # DEC of sun's velocity
define VSUN 20. # VLSR of sun
define EPOCH 1900. # Epoch of sun's velocity
# AST_VSUN -- Projection of the sun's velocity along the given direction.
procedure ast_vsun (ra, dec, epoch, v)
double ra # Reference right ascension (hours)
double dec # Reference declination (degrees)
double epoch # Epoch (years)
double v # VLSR of sun along reference direction
double ravsun, decvsun, vx, vy, vz, cc, cs, s
begin
# Precess VLSR direction to current date.
call ast_precess (double (RAVSUN), double (DECVSUN), double (EPOCH),
ravsun, decvsun, epoch)
# Cartisian velocity components of the sun's velocity.
vx = VSUN * cos (DEGTORAD (15. * ravsun)) * cos (DEGTORAD (decvsun))
vy = VSUN * sin (DEGTORAD (15. * ravsun)) * cos (DEGTORAD (decvsun))
vz = VSUN * sin (DEGTORAD (decvsun))
# Direction cosines along the reference direction.
cc = cos (DEGTORAD (dec)) * cos (DEGTORAD (15. * ra))
cs = cos (DEGTORAD (dec)) * sin (DEGTORAD (15. * ra))
s = sin (DEGTORAD (dec))
# Project sun's motion along the reference direction.
v = -(vx * cc + vy * cs + vz * s)
end
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