NAME

ymkmu -- Create a MULTISPEC WCS based on wavelength tables for FOS.

USAGE

ymkmu input output

DESCRIPTION

This task takes input spectra and wavelength tables, uses the IRAF curfit routines to fit the wavelength table, creates a MULTISPEC world coordinate system (WCS) description of the fit, and creates a new copy of the input spectrum with the new WCS.

This task is intended to be used with the Hubble Space Telescope (HST) spectrographic data from Faint Object Spectrograph (FOS) to merge the wavelengths that result from the calibration into the data itself so that other IRAF tasks, such as splot, may be used.

This particular task is a cl script design specifically for FOS data to be used with the mkmultispec task. To get more information about mkmultispec, see the help for that task.

What the script does is use the "weight" option of mkmultispec to mask out those regions of FOS data that contain no wavelength information. This allows FOS PRISM mode spectra and other gratings which do not illuminate the entire diode array to be used with mkmultispec.

PARAMETERS

input [file name template]

Input files that are to have the new MULTISPEC WCS applied.

These should be FOS ACCUM or RAPID mode data.

output [file name template]

The names of the output spectra.

If this parameter is blank, the spectra will be modified in-place. If file names are specified, there must be the same number of output spectra as input spectra.

(wave = "") [file name template]

List of wavelength images or tables to use in determining the function pixel-to-wavelength transformation.

If no wavelength images/tables are specified, it is assumed that the wavelength images can be found by taking the rootname of the input images and appending the extension .c0h to the name.

If only one wavelength table is specified, the resulting MULTISPEC WCS will be applied to all input spectra. If more than one input wavelength is specified, there must be the same number of wavelength specifications as input spectra. The files may either be a tables or images. If a file is a table, the columns to use are specified as follows: tablename[columnname1,columnname2,...]. If no columns are specified, mkmultispec assumes all columns contain wavelength information.

(function = "legendre") [string, Allowed values: legendre | chebyshev |

spline3 | spline1 | table]

The type of function to fit to the wavelength tables. If "table" is specified, the wavelength data are written directly into the input file headers. If the input is multigroup and "table" is specified, only one table will be applied to all the groups of the input. If interactive mode were chosen, the parameter will be set to the last function specified by the ":function" command.

(nterms = 4) [integer]

The number of terms or spline pieces to fit. For legendre and chebyshev, this is the number of coefficients the fit will have. For spline3, the number of coefficients will be nterms + 3. For spline1, the number of coefficients will be nterms + 1. If interactive mode were chosen, the parameter will be set to the last value specified by the ":order" command.

(label = "Wavelength") [string]

The label to use for the wavelength axis in plots generated using the MULTISPEC information, such as those produced by the task splot.

(units = "Angstroms") [string]

The units the wavelength solution is in. This will be displayed by tasks which use the MULTISPEC information, such as splot.

(low_reject = 2., high_reject = 4.) [real, min = 0.]

Rejection limits below and above the fit in units of the residual sigma. Unequal limits are used to reject spectral lines on one side of the continuum during continuum fitting. If interactive mode were chosen, the parameters will be set to the last values specified by the ":low_reject" and ":high_reject" commands.

(niterate = 0) [integer]

Number of rejection iterations. If set to "0", then no rejection is done while fitting. If interactive mode were chosen, the parameter will be set to the last value specified by the ":niterate" command.

(grow = 1.) [real]

When a pixel is rejected, pixels within this distance of the rejected pixel are also rejected. If interactive mode were chosen, the parameter will be set to the last value specified by the ":grow" command.

(format = "%g") [string]

The format to use to write the coefficients to the image header. The main use is when the table function has been specified and the user wants to conserve header space by specifying a more restrictive format.

(interactive = no) [boolean]

Use the icfit task to interactively fit the wavelengths?

The following parameters apply only for interactive fitting.

(device = "stdgraph") [string]

The graphics device to use for the interactive curve fitting.

(markrej = yes) [boolean]

Mark rejected points?

If you are rejecting many points, you might not want to mark rejected points. If interactive mode were chosen, this parameter will be set to the last value specified by the ":markrej" command.

(verbose = yes) [boolean]

Display names of input and output files while operating on files?

EXAMPLES

1. Convert a series of FOS observations. The wavelengths will be found in the corresponding .c0h images for the input list of images. The output images will have a "_ymkmu" appended to the rootname.

	cl> ymkmu y*.c1h y*%.c1h%_ymkmu.c1h%

REFERENCES

Jonathan Eisenhamer

HELP

For assistance using this or any other tasks, please contact help@stsci.edu or call the help desk at 410-338-1082.

SEE ALSO

mkmultispec, curfit, icfit, splot, onedspec