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These contain the multiple spectra, and any further reduced data or calibration frames. One might also have direct images for use with target selection and astrometry.
Images can be READ into slots in the LEXT image stack. When an image is read into LEXT, a copy of the disk image is made, and it is this copy which is then worked on. For this reason, many of the LEXT commands work on the data in situ. In order to save a modified image it must be written out again with the WRITE command.
Within the image structure, along with the data-array itself, is a descriptive and a . is a description of the contents, purely for user information. The is used by LEXT in certain instances which will be described in the appropriate sections below.