Next: Attributes which Qualify Spectral Up: ss_specframesSpectral Coordinate Systems (SpecFrames) Previous: Creating a SpecFrame
Selection of a particular coordinate system is performed simply by setting a value for the SpecFrameSpecFrame's (character string) SystemSystem attribute. This setting is most conveniently done when the SpecFrame is created. For example, a SpecFrame representing Energy would be created by:
Note that specifying ``System
Energy'' also changes the associated
Unit (from metres to Joules). This is because the default value
of the SpecFrame's Unit attribute depends on the System attribute setting.
You may change the System value at any time, although this is not usually needed. The values supported are set out in the attribute's description in Appendix C and include a variety of velocity systems, together with frequency, wavelength, energy, wave-number, etc.