%% @(#)extinclong.hlq	19.1 (ESO-IPG) 02/25/03 14:24:03
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      extinclong.hlq
%.AUTHOR     JDP, IPG/ESO
%.KEYWORDS   MIDAS, help files, EXTINCTION/LONG
%.PURPOSE    On-line help file for the command: EXTINCTION/LONG
%.VERSION    1.0  13-JUN-1986 : Creation, JDP
%----------------------------------------------------------------
\se
SECTION./LONG
\es\co
EXTINCTION/LONG					    29-MAR-1993    PB
\oc\su
EXTINCTION/LONG  in  out  [scale]  [table]  [col]
	correct spectra for interstellar or atmopsheric extinction
\us\pu
Purpose:      
              Correct spectra for interstellar or atmopsheric extinction.
\up\sub
Subject:      
              Spectroscopy, Calibration, Extinction.
\bus\sy
Syntax:       
              EXTINCTION/LONG in  out  [scale]  [table]   [col]
\ys\pa
              in       = the frame to be corrected for extinction. It must be
                         a 1D rebinned spectrum.
\ap\pa
              out      = the frame to hold the corrected data
\ap\pa
              scale    = the scaling factor: \\
                         a) E(B-V) if interstellar reddening  \\
			 b) AIRMASS if atmospheric extinction. \\
                         If scale=0, the scale will be defaulted to 
                         the AIRMASS descriptors from the frame. Otherwise,
                         the indicated value will be taken as airmasss. \\
                         Default: 0
\ap\pa
              table    = the table with the wavelength dependence of the
                         reddening or the atmospheric extinction. \\
                         Session keyword: EXTAB; default: atmoexan.tbl
\ap\pa
              col      = Number of the transmission column in the  \\
                         atmospheric extinction table; default: 2
\ap\no
Note:         The table supported by MIDAS to correct for interstellar
              extinction is:

              1a) INSTEXAN contains in column \#1 the wavelength in Angstroem
              units and in columns 2-8 seven different extinction laws the
              references for which are as follows:
\\
              col. 2: Savage, B.D., Mathis, J.S.,
                      Ann. Rev. Astron. Astrophys. No. 17, 73 (1979): Galaxy
\\
              col. 3: Nandy et al., MNRAS Vol. 196, 955 (1981): LMC
\\
              col. 4: Prevot et al., Astron. Astrophys. Vol. 132, 389 (1984):
                      SMC
\\
              col. 5: Koornneef, J., Code, A.D., ApJ Vol. 247, 860 (1981): LMC
\\
              col. 6: Seaton, M.J., MNRAS Vol. 187, 73P (1979): Galaxy fit
\\
              col. 7: Howarth, I.D., MNRAS Vol. 203, 301 (1983): Galaxy fit
\\
              col. 8: Howarth, I.D., MNRAS Vol. 203, 301 (1983): LMC fit

              All laws are normalized to A/E(B-V) = 3.1 at 5550 A and
              interpolated and rebinned to constant step in wavelength (10 A).
	      Note that the wavelength coverage is very different for the
              various data sets.

	      1b) The contents of INSTEXNM is the same except for use with
              spectra calibrated in nanometers

	      Correction for atmospheric extinction is possible with:

	      2a) atmoexan.tbl containing the wavelength in Angstroem units
	      in column \#1 and the extinction law for La Silla as described
              by H. Tug in the ESO Messenger No.11, December 1977, and
              listed in the ESO User's Manual.
\\
	      2b) ATMOSNM which is identical to atmoexan.tbl except for
              wavelengths in nm

	      If "scale" is defaulted, descriptor "AIRMASS" is read from
              frame "inframe".

              These tables are stored in MID_EXTINCTION:
\on\exs
Examples:
\ex
              EXTINCTION/LONG observed corrected
\xe \sxe
