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% @(#)offseteche.hlq 19.1 (ESO-IPG) 02/25/03 14:18:37
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%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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%.COPYRIGHT (c) 1993 European Southern Observatory
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%.KEYWORDS MIDAS, help files,
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%.PURPOSE On-line help file for the command: OFFSET/ECHELLE
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%.VERSION 1.0 17-MAR-95 : Creation, PB
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%----------------------------------------------------------------
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OFFSET/ECHELLE 17-MAR-95 PB
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OFFSET/ECHELLE [image] [range] [cover] [ordtab] [mode]
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Determines the offset along the slit between the order
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coefficients and a given echelle spectrum.
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In reason of different positioning along the slit,
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echelle observations might present an offset with respect
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to the image used to define the order positions. The command
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OFFSET/ECHELLE determines this offset by performing a number
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of offset measurement at random positions on a raw spectrum.
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OFFSET/ECHELLE [image] [range] [cover] [ordtab] [mode]
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image = Image name (echelle spectrum at standard orientation).
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By default the image in the display window is used
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for offset measurement.
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range = Range of search for the offset (default 20 pixels)
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cover = Number of measurement points (default 30)
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ordtab = Name of the order table (Default: sess. keyw. ORDTAB)
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mode = Mode of action (Verb, Silent). Default mode is
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Verbose in which the OFFSET keyword is set to the
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measured offset value (the OFFSET keyword is used by
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the EXTRACT/ECHELLE command). In mode Silent
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the offset value is stored in OUTPUTR(1) and the
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OFFSET keyword is left unchanged.
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DEFINE/ECHELLE, DEFINE/HOUGH, EXTRACT/ECHELE, LOAD/ECHELLE
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1) The algorithm involves the measurement of the offset
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at a number of positions selected randomly over the frame.
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Although the algorithm is robust to particle hits, it is
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possible to filter the image before processing. The signal
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to noise of the spectrum should be sufficient to allow the
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unambiguous detection of the central peak of the orders.
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OFFSET/ECHELLE value1 value2