atmospheric correction

Frank Valdes wrote on Jan 29, 1998

Q:  I am doing some slit spectra reduction and have completed the
extraction
and wavelength calibration. I have to preserve the flux information for
all the stars I observed at the Siding Spring Observatory.
Therefore, I would like to correct for the atmospheric features and
overall extinction, as well as subsequently doing the calibration using
standard stars. No mention of how to do this is made in my guide to IRAF
(a user's guide to reducing slit spectra with IRAF), where only the
overall extinction is considered. 
In fact, I wanted to use B-stars(flat spectrum) to do this task, but I
cannot find any command relating to this doing.
Please help

P.S: I ahve followed the steps mentionned in my guide for a sample of
stars and I manage to get calibrated ones, but their spectra  contain
just too many atmospheric absorption features.



A: There is a task in V2.11 IRAF called "telluric" which uses B-stars to
remove telluric features.  This task was written after the user's
guide and so it is not mentioned or described.  Prior to the new task
you would have to do all the scaling and ratioing using general
image/spectrum processing tools such as SPLOT.  Let me know if you
need more information.

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Last post on Jan 29, 1998