A Routine Descriptions

  ECH_BLOCKBLOCKDATA to initialise spectrograph configuration
  ECH_COLLIMATOR— Determine which collimator to use at a given wavelength
  ECH_DISP— Determine the dispersion in mm for a given wavelength
  ECH_FORMAT_CENTRE— Determine the appropriate spectrograph settings
  ECH_FRSPR— Determine the free spectral range in Angstroms
  ECH_INIT— Initialise COMMON blocks for a specified instrument combination
  ECH_LOAD— Load COMMON blocks describing spectrograph parameters
  ECH_ORDERNUM— Determine the order number of a specified wavelength
  ECH_PRISMPOS— Determine the optimal prism rotation and position
  ECH_REFINDEX— Determine the refractive index of fused silica
  ECH_SLITANGLE— Determine the optimum slit angle
  ECH_WAVECEN— Determine the central wavelength of the order
  ECH_WCENTRAL— Determine the central wavelength in Angstroms
  ECH_XDISPFS— Determine the cross-dispersion in mm for a given wavelength

This section contains details of each routine. In particular, refer to the descriptions of the ECH_LOAD and ECH_INIT routines for details of how to create and use spectrograph parameter files, and refer to the description of the ECH_FORMAT_CENTRE routine for details of how the spectrograph configuration for a specified wavelength is determined.