- NAME
VACTOAIR
- PURPOSE
Convert vacuum wavelengths to air wavelengths
- EXPLANATION
Corrects for the index of refraction of air under standard conditions.
Wavelength values below 2000 A will not be altered. Accurate to
about 10 m/s.
- CALLING SEQUENCE
VACTOAIR, WAVE_VAC, [WAVE_AIR]
- INPUT/OUTPUT
WAVE_VAC - Vacuum Wavelength in Angstroms, scalar or vector
If the second parameter is not supplied, then this will be
updated on output to contain double precision air wavelengths.
- OPTIONAL OUTPUT
WAVE_AIR - Air wavelength in Angstroms, same number of elements as
WAVE_VAC, double precision
- EXAMPLE
If the vacuum wavelength is W = 2000, then
IDL> VACTOAIR, W
yields an air wavelength of W = 1999.353 Angstroms
- METHOD
Formula from Ciddor 1996 Applied Optics , 35, 1566
- REVISION HISTORY
Written, D. Lindler 1982
Documentation W. Landsman Feb. 1989
se Ciddor (1996) formula for better accuracy in the infrared
Added optional output vector, W Landsman Mar 2011