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, etc (see the description of the System attribute for
By setting a value for thr SpecOrigin attribute, a SpecFrame can be made to represent offsets from a given spectral position, rather than absolute
’, STATUS )
’System=VELO, RestFreq=1.0E15, StdOfRest=LSRK
’, STATUS )
") axis with rest frequency 1.0E15 Hz (about 3000 Angstroms), measured in the kinematic Local Standard of Rest (
"). Since the source position has not been specified (using attributes RefRA and RefDec), it will only be possible to align this SpecFrame with other SpecFrames which are also measured in the LSRK standard of rest.
When conversion between two SpecFrames is requested (as when supplying SpecFrames AST_CONVERT), account will be taken of the nature of the spectral coordinate systems they represent, together with any qualifying rest frequency, standard of rest, epoch values, etc. The AlignSystem and AlignStdOfRest attributes will also be taken into account. The results will therefore fully reflect the relationship between positions measured in the two systems. In addition, any difference in the Unit attributes of the two systems will also be taken into account.
A null Object pointer (AST__NULL) will be returned if this function is invoked with STATUS set to an error value, or if it should fail for any reason.