The next step is to scrunch the wavelength calibrated OBJE and ARCE files, using SCRUNCH (not ISCRUNCH), which uses the 2D .X.DATA array produced by ECHARC as its source of wavelength information.
Since echelle have a fixed velocity interval per pixel irrespective of wavelength, a logarithmic wavelength scale will have bins that each correspond to the same number of pixels, whereas a linear wavelength scale will give bins at the red end that significantly oversample the resolution element relative to bins at the blue end. Nevertheless, a linear scrunch is usually the favoured option.
Use EXAM to look at the .X structure to find out the minimum and maximum wavelengths before running SCRUNCH.
$ SCRUNCH
(SPectrum) Spectrum to be scrunched [OBJE] -
(LOg) Bin into logarithmic wavelength bins? [NO] -
(WStart) Wavelength of center of first bin [4000] -
(WEnd) Wavelength of center of last bin (or increment) [5000] -
(BIns) Number of bins for scrunched spectrum [25001] -
(Mean) Conserve mean value (as opposed to flux)? [NO] -
(Quad) Use quadratic interpolation for data? [YES] -
(OUtput) Name of scrunched spectrum [ ] - OBJS
Every order will be scrunched into the full wavelength range (4000 to 5000Å with an increment size of 0.04 Å in the above example), so most pixels will be zero.