% @(#)refraclong.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:55:40
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      refraclong.hlq
%.AUTHOR     Alexander Goerdt, Universitaet Sternwarte Goettingen
%.E-MAIL     agoerdt@uni-sw.gwdg.de  or AGOERDT@USW007.DNET.GWDG.DE
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: REFRACTION/LONG
%.VERSION    1.0  01-DEC-94 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./LONG
\es\co
REFRACTION/LONG					      01-DEC-94  AG
\oc\su
REFRACTION/LONG  inim outim [mode]
	Differential atmospheric correction for slit spectra
\us\pu
Purpose:    
            Long slit observations suffer from differential atmos-
            pheric refraction even at moderate airmass conditions.
            Light losses for all wavelengths of your input image
            are calculated and added to the output spectra,
            which contains the intrinsic flux you would observe
            without any light losses due to diff. refraction and slit size.
            The parallactic angel of the slit you should (have) observe(d) 
            your target with, is given to minimize light losses. 
\up\sy
Syntax:     
            REFRACTION/LONG inim outim [mode]
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\ys\pa
            inim = input  image (one-dimensional)
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\ap\pa
            outim = output image (one-dimensional)
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\ap\pa
            mode  = interaction mode (INTERACTIVE or AUTO)
                    In mode INTERACTIVE, the user is prompted to
                    provide the different parameters. In mode AUTO
                    the values are read from keywords INPUTC, INPUTI, 
                    INPUTR, as indicated in the Note.
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\ap\sa
See also: 
            EXTINCTION/LONG, CALIBRATE/FLUX
\as\no
Note:       
            During calculations you are asked for:

                1) The unit of the spectrum                  [INPUTI(1)]
                   (1=Angstroem, 2=nm, 3=m, 4=other)
                   and if the option other (4) was chosen:
                   The exponent of the unit                  [INPUTI(2)]

                2) Observing site (telescope)                [OUT_B(1:9)]
                     or coordinates
                       a) latitude [degree (-90 to 90)]      [INPUTR(2)]
                       b) longitude [degree (-180 to 180)]   [INPUTR(3)]
                       c) altitude [meter]                   [INPUTR(4)]
                3) Temperature [deg. Celsius] (at observing time) [INPUTR(5)]
                4) Water contents of atmosphere              [INPUTR(6)]
                   (Moisture, see interactiv graphic) 
                5) Target coordinates                      
                       a) right ascension [hh.mmss]          [INPUTR(7)]
                       b) declination [hh.mmss]              [INPUTR(8)]
                6) wavelength [Angstrom] (centered to  the slit) [INPUTR(9)]
                7) Seeing [arcsec]                           [INPUTR(10)]
                8) astronomical angle [degree]               [INPUTR(11)]
                   (of slit you want to observe with)
                9) Slit size
                       a) length [arcsec]                    [INPUTR(12)]
                       b) width [arcsec]                     [INPUTR(13)]
               10) Observing date
                       a) year                               [INPUTI(3)]
                       b) month                              [INPUTI(4)]
                       c) day                                [INPUTI(5)]
                11) Observing time [U.T.] (start of exposure) [INPUTR(14)]
                12) exposure time [min]                      [INPUTR(1)] 
                     (the time the program will use is : 
                      observing time + 1/2 exposure time)
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           References:
               1)  C.W. Allen, Astrophy. Quantities, 3rd edition p.118ff
               2)  De Ball, Lehrbuch der sph. Astronomie, Leipzig 1912 
               3)  Duffett-Smith, Practical Astr. with your Calculater
               4)  Filippenko, A., P.A.S.P. (1982), 94, p.715
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\on\exs
Examples:
\ex
            REFRACTION/LONG  spectrum  spec2
\xe \sxe