Should the SideBand attribute be taken into account when aligning this DSBSpecFrame with another DSBSpecFrame?


This attribute controls how a DSBSpecFrame behaves when an attempt is made to align it with another DSBSpecFrame using AST_FINDFRAME or AST_CONVERT. If both DSBSpecFrames have a non-zero value for AlignSideBand, the value of the SideBand attribute in each DSBSpecFrame is used so that alignment occurs between sidebands. That is, if one DSBSpecFrame represents USB and the other represents LSB then AST_FINDFRAME and AST_CONVERT will recognise that the DSBSpecFrames represent different sidebands and will take this into account when constructing the Mapping that maps positions in one DSBSpecFrame into the other. If AlignSideBand in either DSBSpecFrame is set to zero, then the values of the SideBand attributes are ignored. In the above example, this would result in a frequency in the first DSBSpecFrame being mapped onto the same frequency in the second DSBSpecFrame, even though those frequencies refer to different sidebands. In other words, if either AlignSideBand attribute is zero, then the two DSBSpecFrames aligns like basic SpecFrames. The default value for AlignSideBand is zero.

When AST_FINDFRAME or AST_CONVERT is used on two DSBSpecFrames (potentially describing different spectral coordinate systems and/or sidebands), it returns a Mapping which can be used to transform a position in one DSBSpecFrame into the corresponding position in the other. The Mapping is made up of the following steps in the indicated order:

Integer (boolean).


All DSBSpecFrames have this attribute.