This attribute holds refractive index of the grism material at the reference wavelength (given by attribute GrismWaveR). The default value is 1.0.

Note, the value of this attribute may changed only if the GrismMap has no more than one reference. That is, an error is reported if the GrismMap has been cloned, either by including it within another object such as a CmpMap or FrameSet or by calling the AST_CLONE function.

GrismMap