Standard orientation

The frames, as they appear on the monitor with the command LOAD/IMAGE, are in general not oriented properly. All reduction programs assume that on the monitor the wavelength increases from left to right and that the spectral orders increase from top to bottom. This means that the frames have to be rotated in such a way that:

• orders are more or less horizontal, but slightly climbing from left to right.
• orders separation are narrower at the bottom than at the top.

The images have to be rotated, depending on the way the CCD chip has been mounted. To do this, prepare again a catalogue containing all files which have to be rotated using CREATE/ICAT. Next run the program

ROTATE/ECHELLE inputspec outframe mode

Note rotation is usually required for CASPEC, EFOSC, ECHELLEC, and EMMI spectra. The command ROTATE/ECHELLE sets descriptor values START and STEP to 1.,1. for all images and updates the session keyword CCDBIN to the original steps of the images. These operations must be performed by the user if another command than ROTATE/ECHELLE is applied.

As in PREPARE/WINDOW, inputspec is either a single input frame or a catalogue; outframe is either a single output frame or a two character identifier which will replace the first two characters of the name of each input frame; mode decides if the images are just rotated over -90 degrees (mode ROTATE, data obtained before April 1984) or rotated over 90 degrees and flipped in the x-direction (mode FLIP) for frames obtained later. This command will also read the exposure time from the descriptor O_TIME, prompting for it if the descriptor is not present.