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SpecFrame - Spectral coordinate system description

Description:
A SpecFrame is a specialised form of one-dimensional Frame which represents various coordinate systems used to describe positions within an electro-magnetic spectrum. The particular coordinate system to be used is specified by setting the SpecFrame's System attribute (the default is wavelength) qualified, as necessary, by other attributes such as the rest frequency, the standard of rest, the epoch of observation, units, etc (see the description of the System attribute for details).

By setting a value for thr SpecOrigin attribute, a SpecFrame can be made to represent offsets from a given spectral position, rather than absolute spectral values.

Constructor Function:
astSpecFrame
Inheritance
The SpecFrame class inherits from the Frame class.
Attributes
In addition to those attributes common to all Frames, every SpecFrame also has the following attributes:

Several of the Frame attributes inherited by the SpecFrame class refer to a specific axis of the Frame (for instance Unit(axis), Label(axis), etc). Since a SpecFrame is strictly one-dimensional, it allows these attributes to be specified without an axis index. So for instance, "Unit" is allowed in place of "Unit(1)".
Functions
In addition to those functions applicable to all Frames, the following functions may also be applied to all SpecFrames:

  • astSetRefPos: Set reference position in any celestial system

  • astGetRefPos: Get reference position in any celestial system


next up previous 264
Next: SpecMap - Sequence of spectral coordinate conversions
Up: AST Class Descriptions
Previous: SpecFluxFrame - Compound spectrum/flux Frame

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
7th December 2012
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2012 Science \& Technology Facilities Council