-- SFLIP---Flip Data or Dispersion Coordinates in Spectra

SFLIP---Flip Data or Dispersion Coordinates in Spectra

A new task called sflip, for flipping spectra has (re)appeared in IRAF V2.10.3BETA / V2.11. The task has four parameters, an input list of spectra, an output list, a parameter to select whether to flip the dispersion coordinates, and a parameter to select whether to flip the data (storage order in the image) along the dispersion axis. The task allows the output to be the same as the input to modify images rather than create new ones.

Besides providing an easily identifiable task for spectroscopy users this task's principal purpose is to separate flipping of the data and the coordinate system. Using image sections to flip spectra, say with imcopy, flips both the dispersion coordinates and data. To only flip the data or the coordinate system using the general system tasks requires several steps and some knowledge of the WCS coordinate system.

Actually this task is not entirely new since there was a task by that name in V2.9. The new task has much the same function but is implemented differently because of changes in how dispersion coordinate systems are handled. In principle this task should never be needed since the spectral software (V2.10 and beyond) works in dispersion coordinates, but there are rare cases, mainly to do with interfacing to user programs outside of IRAF, when it may be of use.

Frank Valdes

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