% @(#)refracopto.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:54:57
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT      (c) 1991 European Southern Observatory
%.IDENT          atref.hlq
%.AUTHOR         A. Gemmo     Padova Department of Astronomy
%.KEYWORDS       MIDAS, help files, REFRACTION/OPTOPUS
%.PURPOSE        On-line help file for the command: REFRACTION/OPTOPUS
%.VERSION        1.0 16-SEP-1991 : Creation, AG
%----------------------------------------------------------------------
\se
SECTION./OPTO
\es\co
REFRACTION/OPTOPUS                              16-SEP-1991 AG
\oc\su
REFRACTION/OPTOPUS [inp_tab] [out_tab] [year,month,day] [exp] [lambda1,lambda2]
                   [start_st_slot,end_st_slot] [opt_st] [ast_flag]
	correct for atmospheric refraction X and Y coord. on Optopus plate.
\us\pu
Purpose:    
            Correct for atmospheric refraction effects X and Y
	    coordinates of objects on Optopus plate. For given
	    plate-center coordinates (they must the same used by 
	    the command HOLES/OPTOPUS), specified observation time
	    slot and wavelength range of interest, REFRACTION/OPTOPUS
	    determines: (a) an optimal differential correction vector,
	    (b) an optimal chromatic correction vector for the
	    guidestars.
            In the end, all the relevant parameters determined by 
	    REFRACTION/OPTOPUS are written into descriptors of the 
	    output table, so that they can be read by READ/DESCRIPTORS
	    or printed by PRINT/DESCRIPTORS commands.
\up\sy
Syntax:     
            REFRACTION/OPTOPUS [inp_tab] [out_tab] [year,month,day] [exp] 
              [lambda1,lambda2] [start_st_slot,end_st_slot] [opt_st] [ast_flag]
\ys\pa      
	    [inp_tab]           = table created by the command HOLES/OPTOPUS,
			          which contains X and Y coordinates of
			          positions of holes on Optopus plate. Default
			          name is "opto2.tbl".
\ap\pa      
	    [out_tab]           = output table, with corrected X and Y
			          coordinates and column :NUMBER, which
			          sequentially identifies holes on starplate.
                                  Its descriptors contain all relevant
			          parameters created or updated by 
			          REFRACTION/OPTOPUS. Default name is
			          "opto3.tbl".
\ap\pa     
	    [year,month,day]    = \\date of the observation. The permitted
			          input formats are:\\
			          (1) YEAR,MONTH(number),DAY or\\
			          (2) YEAR.yyyyy,0,0\\
			          Default value is "1999.,12.,31.".
\ap\pa
	    [exp]               = Exposure time in minutes of Optopus
	                          plate. Default value is "0.".
\ap\pa      
	    [lambda1,lambda2]   = \\Wavelength range to optimize the
				  corrections for atmospheric refraction.
				  Input format must be: LAMBDA1,LAMBDA2
				  both in Angstroem. Default value is:
	                          "3800,8000".
\ap\pa
	    [st_st_sl,en_st_sl] = \\Sidereal time slot, that is sidereal
				  time interval during which a given
				  Optopus plate will probably be used.
				  Input format must be:
				  ST1.ss,ST2.ss. Default value is:
				  "00.00,00.00".
\ap\pa
	    [opt_st]            = Optimal sidereal time for correction
				  determinations, that is sidereal time
				  for which the corrections for
				  atmospheric refraction are calculated.
				  Input format must be: ST.ss.
				  Default value is: "00.00".
\ap\pa
	    [ast_flag]          = Y or y (for yes) and N or n (for no)
				  are the alternatives. An [ast_flag]
				  set to Y enables the automatic
				  determination of the optimal sidereal
				  time for correction determinations 
				  (see parameter [opt_st]). An input
				  from the user is otherwise requested.
                                  Default value is "Y".
\ap\no
Note:     
          Any parameter of REFRACTION/OPTOPUS command can be defaulted.
	  It is actually possible to default all of them having
	  previously used the SET/OPTOPUS command (see documentation) to 
	  select convenient values which will be stored in keywords 
	  initialized in Optopus context.
\\
          To correctly determine the sidereal time slot, it is useful to
	  have a test run of the command REFRACTION/OPTOPUS before
	  actually using it. This way one gets the sidereal times of the
	  beginning and end of the night, that is its duration, which
	  can be divided by 4 or 5, depending on how many Optopus plates
	  one wants to use, to get the 4 (or 5) sidereal time slots
	  (take care to allow for some 15-20 minutes of "warming up" at
	  the beginning of the night, of course).
\\
	  It is a good idea always to save all the parameters used in
	  an Optopus session by writing them into the descriptors of
	  the last created table, typically the output table of
	  REFRACTION/OPTOPUS, with the command SAVE/OPTOPUS tablename,
	  (see documentation). It will be possible later to retrieve
	  them by using RESTORE/OPTOPUS tablename (see documentation).
\\
          We consider useful to remind here that it is possible to 
	  have a print-out of the descriptors of any table by using the
	  commands:\\
	  (1) ASSIGN/PRINTER FILE filename\\
	  (2) PRINT/DESCRIPTORS table *\\
          The descriptors values will be in the ASCII file "filename".
\on\exs
Examples:
\ex
	  REFRACTION/OPTOPUS op2 op3
\xe\ex
	  REFRACTION/OPTOPUS op2 op3 1991,10,9 60 4000,8000 20,22 21 n
\xe\ex
	  REFRACTION/OPTOPUS op2 op3 1991,10,9 60 4000,7500 20,22 ? y
\xe\ex
	  REFRACTION/OPTOPUS op2 op3 1991,10,9 60 ? 20,22 ? Y
\xe\sxe