This attribute is a boolean value which controls how a SpecFrame behaves when it is used (by AST_FINDFRAME or AST_CONVERT) as a template to match another (target) SpecFrame. It determines whether alignment occurs between the offset values defined by the current value of the SpecOffset attribute, or between the corresponding absolute spectral values.

The default value of zero results in the two SpecFrames being aligned so that a given absolute spectral value in one is mapped to the same absolute value in the other. A non-zero value results in the SpecFrames being aligned so that a given offset value in one is mapped to the same offset value in the other.

SpecFrame