The central position of interest in a dual sideband spectrum
"
observed"
sideband, and the other sideband as the "
image"
sideband.
The value is accessed as a position in the spectral system represented by the SpecFrame attributes
inherited by this class, but is stored internally as topocentric frequency. Thus, if the System attribute of
the DSBSpecFrame is set to "
VRAD"
, the Unit attribute set to "
m/s"
and the StdOfRest attribute set
to "
LSRK"
, then values for the DSBCentre attribute should be supplied as radio velocity in units
of "
m/s"
relative to the kinematic LSR (alternative units may be used by appending a
suitable units string to the end of the value). This value is then converted to topocentric
frequency and stored. If (say) the Unit attribute is subsequently changed to "
km/s"
before
retrieving the current value of the DSBCentre attribute, the stored topocentric frequency
will be converted back to LSRK radio velocity, this time in units of "
km/s"
, before being
returned.
The default value for this attribute is 30 GHz.