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% @(#)extracopti.hlq 19.1 (ESO-IPG) 02/25/03 14:18:33
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%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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%.COPYRIGHT (c) 1990 European Southern Observatory
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%.AUTHOR MP, IPG/ESO; SW, DMD/ESO
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%.KEYWORDS MIDAS, help files, EXTRACT/OPTIMAL
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%.PURPOSE On-line help file for the command: EXTRACT/OPTIMAL
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%.VERSION 1.0 28-NOV-1991 : Creation, MP
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% 2.0 09-SEP-1999 : cosmic ray rejection, variance calculation
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% and calc parameter added.
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%----------------------------------------------------------------
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EXTRACT/OPTIMAL 09-SEP-1999 MP/SW
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EXTR/OPT input output slit,ord1,ord2 [ron,g,sigma] [table] [coeffs] [calc]
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weigthed extraction of echelle orders
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Extract echelle orders. Position of the orders are defined
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in the auxiliary table order.tbl, generated with the command
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DEFINE/ECHELLE or DEFINE/HOUGH. Orders are extracted by
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calculating a weighted sum of the pixels values across the
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profile of the object. The algorithm is based on a paper from
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Koji Mukai(1990, Optimal Extraction of Cross-Dispersed Spectra,
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Pub. of Astr. Soc of the pacific,102:183-189).
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Syntax: EXTR/OPT in out slit,ord1,ord2 [ron,g,sigma] [table] [coeff] [calc]
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in = input image sampled in the usual pixel-pixel space
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out = extracted image sampled in the space pixel-order
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slit = numerical slit length in pixels
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ord1,ord2 = number of the first and last order to extract.
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Relative order numbers are displayed by the
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ron,g,sigma = read-out-noise(e-), inverse gain factor (e-/ADU),
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threshold for the removal of cosmic ray hits
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(in units of the standard deviation calculated
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for each pixel from the number of electrons and
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If not provided on the command line, these values
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are read from echelle keywords RON, GAIN, EXTSIGMA.
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table = name of the input table providing the order
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definition. Default: order.tbl
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coeff = name of the descriptor providing the coefficients
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of the order definition. Default: COEFF.
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calc = determine/apply weights for optimal extraction.
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Y,name: do an optimal extraction and store the
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N,name: do an optimal extraction using the weights
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name of a previously performed extraction.
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The parameter slit defines the integer length of the numerical
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extraction slit centered on the current order center at every
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position along the dispersion direction. (We suppose that the
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command DEFINE/ECHELLE or DEFINE/HOUGH has been used previously
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to find the position of the orders )
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The weigths are proportional to the mean order profile
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perpendicular to the dispersion direction.
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This version of this command is now able to remove cosmic rays.
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Furthermore, a variance frame of the extracted orders will be
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produced. The variance frame has the same name as the extracted
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data with the prefix 'var_'.
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EXTRACT/OPTIMAL produces averaged spectra in the pixel-order
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space. In order to get the integral extracted orders you only have
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to multiply your result frame by the slit parameter and the
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variance frame by the squared slit parameter.
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EXTRACT/OPT raw extract 6,1,15 40,10.,3.
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Do an optimal extraction of the object
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EXTRACT/OPT obj extrobj 15,1,20 ? ? ? Y,objwght.bdf
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Do an optimal extraction of the flatfield using the same weights
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as for the optimal extraction of the object.
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EXTRACT/OPT flat extrflat 15,1,20 ? ? ? N,objwght.bdf