`ECH_PRISMPOS`

Determine the optimal prism rotation and position

Determine the prism rotation and position by direct calculation. The rotation is such that a ray of the specified wavelength will fall on the centre of the detector. The position is such that the echelle is fully illuminated by rays of the specified wavelength.

`ECH_INIT`

must be called before calling this routine.

`CALL`

`ECH_PRISMPOS`

(`WC`

, `GAMMA`

, `POS`

, `STATUS`

)

`READ` | `WC` | `REAL` | Desired central wavelength (Angstroms) |

`WRITE` | `GAMMA` | `REAL` | Optimal prism rotation (radians) |

`WRITE` | `POS` | `REAL` | Optimal prism position (mm) |

`READ` , `WRITE` | `STATUS` | `INTEGER` | Global status value |

C.J. Hirst `UCL`

(`ZUVAD`

::`CJH`

)