Determine the cross-dispersion in mm for a given wavelength ECH_XDISPFS
Calculate the refractive index at the given wavelength. Then calculate it at the point where the cross-dispersion is by definition zero. Knowing the focal length of the camera, calculate the cross-dispersion in mm on the assumption that the light enters and leaves the prisms at the same angles of incidence (a first order approximation is used).
ECH_INIT must be called before calling this routine.
CALLECH_XDISPFS (WAVE, GAMMA, DEL, STATUS)
READ | WAVE | REAL | Wavelength of point at which cross-dispersion is to be calculated (Angstroms) |
READ | GAMMA | REAL | Echelle gamma angle corresponding to the current configuration (radians) |
WRITE | DEL | REAL | Cross-dispersion (mm) |
READ, WRITE | STATUS | INTEGER | Global status value |
C.J. Hirst UCL (ZUVAD::CJH)