slist: List spectrum header parameters

Package: onedspec

Usage

slist images

Parameters

images: List of images to be listed.

apertures = "": List of apertures to be selected from the images for listing. A null list selects all apertures. See ranges for the syntax of this list.

long_header = no: If set to yes, then a multiline listing of the header elements is given. If set to no, then a single line per spectrum is given. The contents of the listing depend on the format.

Description

This task lists header information from apertures in a list of input images. There is a short one line per spectrum listing and a more extended listing selected by the long_header parameter.

In both short and long outputs the aperture information consists of lines with the following whitespace separated fields: the image line, the aperture number, the beam number, the dispersion type, the wavelength of the first pixel, the wavelength interval per pixel, the number of valid pixels, and the aperture title. The dispersion type is an integer with a value of -1 if not dispersion corrected, 0 if dispersion corrected to a linear wavelength sampling, 1 if dispersion corrected to a log wavelength sampling, and 2 if dispersion corrected to a nonlinear sampling. The wavelength per pixel is an approximation based on the wavelength endpoints divided by the number of pixels in the case of a nonlinear dispersion function. Also the wavelengths refer to the actual pixels taking any image sections into account and so may differ from the coordinate system information in the header which is defined for the original physical coordinates. The aperture titles may be identical with the image title if individual aperture titles are not defined.

In the short output format the image title is given first followed by the above described information. This format is compact and suitable for easy use in other programs (see the example below). The long output format is blocked by image and gives the image name and title on the first line, the exposure time, universal time, and siderial time on the second line, the right ascention, declination, hour angle, and airmass on the third line, and then the individual aperture information on the remaining lines. If some of the header information is missing a value of INDEF is printed. The keywords used are EXPTIME/ITIME/EXPOSURE (in that order) for the exposure time, and UT, ST, RA, DEC, HA, and AIRMASS for the remaining values.

demoobj.ms: Hydra artificial image EXPTIME = 2133.33 UT = 9:10:09.0 ST = 20:09:34.0 RA = 1:34:02.00 DEC = 30:37:03.0 HA = INDEF AIRMASS = 2.3

Examples

1. List short header for an object and arc from a Hydra multifiber reduction for fibers 36 to 39.

cl> slist demoobj.ms,demoarc1.ms ap=36-39
demoobj.ms 1 37 0 0 5785.85 6.140271 256 Sky fiber
demoobj.ms 2 38 1 0 5785.85 6.140271 256 SS313
demoobj.ms 3 39 1 0 5785.85 6.140271 256 SS444
demoarc1.ms 1 36 2 0 5785.85 6.140271 256 Arc fiber
demoarc1.ms 2 37 0 0 5785.85 6.140271 256 Sky fiber
demoarc1.ms 3 38 1 0 5785.85 6.140271 256 SS313
demoarc1.ms 4 39 1 0 5785.85 6.140271 256 SS444

Note that fiber 37 is the first image line in demoobj.ms and teh second image line in demoarc.ms. The dispersion is the same in all fibers by design.

2. List long headers for the two images of example 1 but restricted to apertures 38 and 39.

cl> slist demoobj.ms,demoarc1.ms ap=38,39 l+
demoobj.ms: Hydra artificial image
    EXPTIME = 2133.33 UT = 9:10:09.0    ST = 20:09:34.0
    RA = 1:34:02.00   DEC = 30:37:03.0  HA = INDEF    AIRMASS = 2.3
    2 38 1 0 5785.85 6.140271 256 SS313
    3 39 1 0 5785.85 6.140271 256 SS444
demoarc1.ms: Hydra artificial image
    EXPTIME = 2133.33 UT = 9:10:09.0    ST = 20:09:34.0
    RA = 1:34:02.00   DEC = 30:37:03.0  HA = INDEF    AIRMASS = 2.3
    3 38 1 0 5785.85 6.140271 256 SS313
    4 39 1 0 5785.85 6.140271 256 SS444

The other header parameters are the same because this is artificial data using the same template header.

3. Dump the set of image headers on a printer in long format.

cl> slist *.ms.imh l+ | lprint

4. The short form of SLIST may be used to get some of the aperture information for use in a script. The following simply prints the image line corresponding to a specified aperture. In a real application something more complex would be done.

procedure example (images, aperture)

string  images          {prompt="List of images"}
int     aperture        {prompt="Aperture"}

begin
        string temp, image
        int     line

        # Use SLIST to print to a temporary file.
        temp = mktemp ("example")
        slist (images, aperture=aperture, long=no, > temp)

        # Scan each line and print the line number.
        list = temp
        while (fscan (list, image, line) != EOF)
            print (image, ": ", line)
        list = ""
        delete (temp, verify=no)
end

Revisions

SLIST V2.10: This task was revised to be relevant for the current spectral image formats. The old version is still available in the IRS/IIDS package.