getimage -- Extract an image from the CD-ROM all sky survey
The task getimage is a program for accessing the compressed image data from the CD-ROM set of the Digitized Sky Survey. Given the center coordinates and size of a field, getimage will extract the corresponding data from the CD-ROM discs, uncompress the data, and write them to an image file. The output images may be written as FITS files or GEIS (hhh/hhd) images.
The output filename is formed from a text string, up to four characters in length, that is one of the input parameters. The output filename is a concatenation of this text string and the 4-character plate-id that identifies the plate from which the image was extracted. If the output file is a FITS file, the filename extension is fits; for GEIS files, it is the usual hhh and hhd. Examples of output filenames are Test01d2.fits, or smag01d2.hhh/smag01d2.hhd.
The GetImage software, that comes with the CD-ROM set, must be installed on your system independently of STSDAS. It can be executed in a stand-alone mode or from within the GASP package. The task getimage executes the GetImage software as a foreign task. If you attempt to execute the getimage task and you get an error of the form "getimage: Command not found," you must make certain that the GetImage software directory is in your login path. This will enable you to execute the GetImage software by entering getimage both in stand-alone mode or from within the GASP package of STSDAS.
The mount point of your local CD-ROM reader is one of the hidden parameters of this task. If you are running under UNIX, it must be properly set before executing this task. This parameter is ignored on VMS systems.
If you plan to run the GetImage software both in a stand-alone mode as well as from within the GASP package, you should keep in mind that some of the default values for the parameters of this task are not the same as the default execution options in the stand-alone mode.
- name [string]
- A text string, at most four characters long, that serves as the name of the extracted image. This string is also used as a prefix to form the name of the output file containing the image.
- ra [real]
- The right ascension in the form of hh:mm:ss.sss.
- dec [real]
- The declination in the form of -dd:mm:ss.ss.
- hsize [real]
- The width, or horizontal size, in arcminutes. The default is 14.5 arcminutes, which corresponds to 512 pixels.
- vsize [real]
- The height, or vertical size, in arcminutes. The default is 14.5 arcminutes, which corresponds to 512 pixels.
- equinox [string]
- The equinox of the user specified ra and dec, either J2000 or B1950. The default is J2000.
- filtype [string]
- The format of the output file, either fits or geis. The default is geis.
- exitopt [bool]
- This option determines whether the CD-ROM disk is left mounted or not after getimage has been executed. If you have many images to extract from the same CD-ROM disk, it is convenient to leave that disk mounted. A response of no, leaves the disk mounted. The default is yes.
- cntropt [bool]
- Because the plates overlap somewhat, it is possible for the specified field to be on more than one plate. If this option is yes, only the field closest to a plate center will be extracted. If it is no, all the fields will be extracted.
- mnt_pnt [string]
- The path name of the directory that serves as the mount point for your local CD-ROM reader.
1. Extract an image from the CD-ROM all sky survey
ga> getimage "SMAG" 0:51:5.0 -73:0:15.5 equinox=J2000