functions in doppler.i -

             vacwl=airvac(airwl)  
 
    Compute vacuum wavelength from air wavelength in Angstroms.  
    Information found in;  
    http://www-obs.univ-lyon1.fr/hypercat/pleinpot/imdwaxisc1.html  
    "The IAU standard for conversion from air to vacuum wavelengths is given in  
    Morton (1991,  ApJS, 77, 119).  For vacuum wavelengths (VAC)  in Angstroms,  
    convert  to air wavelength  (AIR) via:  
    AIR =  VAC /  (1.0 +  2.735182E-4 + 131.4182 / VAC^2 + 2.76249E8 / VAC^4)"  

             lambdaofv(v,lambda0)  
 
     
    Returns observed  wavelength corresponding to  lambda0 Doppler-shifted with  
    velocity v.  Wavelength are in vacuum unless AIR is set to non void and non  
    null. If AIR is specified, wavelengths  must be in angstroms, or MICRONS or  
    COEF must be specified too (see airvac and vacair). Velocities are in m/s.  
    If VLSR keyword is  set to the real velocity in the  local standard of rest  
    of an  object which radial  velocity relative to  the earth is zero  at the  
    time of observations, V is considered a velocities in the local standard of  
    rest and apparent wavelengths at  the time of observations are computed. If  
    not, V  should not  be in the  local standard  of rest but  at the  time of  
    observations for the return wavelengths to be accurate.  
    Example:  
    say you have a spectrum of  an object, which velocity in the local standard  
    of rest is 0 but at the time of observations, an observed velocity of 0m/s  
    would indeed  correspond to  a velocity  in the local  standard of  rest of  
    VLSR(m/s).   AXIS contains  the  observed wavelength  in  micron for  this  
    spectrum.   Then, lambdaofv(voflambda(AXIS,vlsr=VLSR),vlsr=0)  would return  
    the axis, corrected for the earth's  motion. Now, if radial velocity of the  
    object in the LSR is not 0,  but Vobj, then the axis corrected for both the  
    earth's       and       object's       motions      is       given       by  
    lambdaofv(voflambda(AXIS,vlsr=VLSR),vlsr=-Vobj). (Note:  don't trust me, at  
    the time I'm writing these lines, I'm quite tired...)  

              LightSpeed  
 
     The  velocity of  light in  vacuum and in m/s.  

             airwl=vacair(vacwl)  
 
    Compute air wavelength from vacuum wavelength in Angstroms.  
    Information found in;  
    http://www-obs.univ-lyon1.fr/hypercat/pleinpot/imdwaxisc1.html  
    "The IAU standard for conversion from air to vacuum wavelengths is given in  
    Morton (1991,  ApJS, 77, 119).  For vacuum wavelengths (VAC)  in Angstroms,  
    convert  to air wavelength  (AIR) via:  
    AIR =  VAC /  (1.0 +  2.735182E-4 + 131.4182 / VAC^2 + 2.76249E8 / VAC^4)"  

             voflambda(lambda,lambda0)  
 
     
    Attention: ALL velocities, including VLSR, are in m/s (NOT in km/s).  
    Returns   radial   velocity   necessary   to   Doppler-shift   lambda0   to  
    lambda. Wavelengths  are in vacuum  unless AIR is  set to non void  and non  
    null. If AIR is specified, wavelengths  must be in angstroms, or MICRONS or  
    COEF must be specified too (see  airvac and vacair). Velocities are in m/s.  
    VLSR keyword can be  used to shift the returned value: VLSR  must be set to  
    the real velocity  in the local standard of rest of  an object which radial  
    velocity relative  to the earth  is zero at  the time of  observations.  In  
    that case, VOFLAMBDA  returns velocities in the local  standard of rest. If  
    not, it returns velocities relative to the observer.