### ECH_FRSPR

Determine the free spectral range in Angstroms

##### Description

Determine the central wavelength of the specified order and then use the grating equation directly to calculate the free spectral range.

ECH_INIT must be called before calling this routine.

##### Invocation

CALLECH_FRSPR (M, THETA, GAMMA, FREE, STATUS)

##### Arguments
 READ M INTEGER Order number for which to calculate the free spectral range READ THETA REAL Echelle theta angle corresponding to the current configuration (radians) READ GAMMA REAL Echelle gamma angle corresponding to the current configuration (radians) WRITE FREE REAL Free spectral range (Angstroms) READ, WRITE STATUS INTEGER Global status value

None known.

##### Authors

C.J. Hirst UCL (ZUVAD::CJH)