In view of the importance of the high redshift studies in today radio-astronomy, it is desirable to handle the observation of high redshift sources in a better way than just replacing the rest frequency by the redshifted frequency at observation time as it is done today at IRAM. It would be better to generalize the formalism to handle both the local and high-redshift universe observations.
In this generalization, the spectral axis would be described with 3
parameters (
,
,
) with the convention that
when
, and vice-versa. This would enable
to keep the information about the redshift and the rest frequency when
observing the high-redshift universe.