COADD-Form the spectrum which is the mean of the rows in an image

Description:

COADD takes a 2-D file as produced by FIGS322 or RCGS2 and combines scans to generate a spectrum with error bars

Parameters:

IMAGE

The name of a 2-D file (wavelength by scan number) as produced, for example, by FIGS322 or RCGS2.

TSTART

The first t-value to be used.

TEND

The last t-value to be used.

YSTART

The first y-value to be used.

YEND

The last y-value to be used.

CUTOFF

Values more than CUTOFF times sigma away from the mean value for the spectral point will not be included in the final spectrum.

SPECTRUM

The name of the resulting single spectrum produced by collapsing down the image.

NORM

NORM=YES causes the data for each cycle to be normalized so that the mean value for each cycle is the same. This gives more reasonable errors when data are taken in the presence of cloud. It should not be used on very faint sources, as the mean level may go negative under these circumstances.

Source comments:

 C O A D D

 Form a spectrum which is the mean of all the rows in an image
 or form an image which is the mean of all the planes in a cube.
 The errors on the result are the standard errors of the mean
 (i.e. SIGMA/SQRT(N) when N rows or planes are combined). Any error
 information in the original image or cube is ignored.

 An XY image is collapsed along the Y direction to give a spectrum,
 and an XYT cube is collapsed along the T direction to give an XY image.

 Typical uses include the combination of the various cycles of a
 CGS2 or FIGS observation as output by the FIGS322 or RCGS2 programs,
 or coadding of CGS4 observations (for this purpose the individual images
 must be first grown into a cube using GROWXY).

 If the NORM keyword is set the errors are calculated after
 normalizing each row or plane so that the mean value is the same
 for all rows (planes). This does not effect the output data but
 generates errors which are determined only by the noise level in the
 data and are not influenced by any general trend in the data.

 If the CUTOFF parameter is specified, points which deviate from the
 mean by more than CUTOFF times the standard error for the mean are
 excluded from the calculation. The mean is recalculated until no
 points exceed the CUTOFF limit. This procedure allows spikes in the
 data to be removed.

 Command parameters -

 'IMAGE'    The name of the input 2-D or 3-D file.
 'YSTART'   (or TSTART) The first Y or T value to use.
 'YEND'     (or TEND) The last Y or T value to use.
 'SPECTRUM' The name of the resulting spectrum or image.
 'CUTOFF'   The level (in sigma) at which a point will
            be ignored.

 Command keywords -

 'NORM'     Normalize data to mean level.

 Input data -

                                 JAB / JAC 7th Dec 1990