GrismMap

Transform 1-dimensional coordinates using a grism dispersion equation

Description:

A GrismMap is a specialised form of Mapping which transforms 1-dimensional coordinates using the spectral dispersion equation described in FITS-WCS paper III " Representation of spectral coordinates in FITS" . This describes the dispersion produced by gratings, prisms and grisms.

When initially created, the forward transformation of a GrismMap transforms input " grism parameter" values into output wavelength values. The " grism parameter" is a dimensionless value which is linearly related to position on the detector. It is defined in FITS-WCS paper III as " the offset on the detector from the point of intersection of the camera axis, measured in units of the effective local length" . The units in which wavelength values are expected or returned is determined by the values supplied for the GrismWaveR, GrismNRP and GrismG attribute: whatever units are used for these attributes will also be used for the wavelength values.

Constructor Function

AST_GRISMMAP

Inheritance

The GrismMap class inherits from the Mapping class.

Attributes

In addition to those attributes common to all Mappings, every GrismMap also has the following attributes:

Functions

The GrismMap class does not define any new routines beyond those which are applicable to all Mappings.