Hi Ellie,
being not versed in radioastronomy, I need to guess a bit here, but:
Is what you want essentially "how much power is there for any Doppler
shift"?
If that's the case, and you're observing some known-frequency emission
(say, a Hydrogen line) would that basically amount to:
1. Frequency-Shifting so that the zero-doppler frequency ends up at 0 Hz
2. transforming your time domain observation to frequency domain
3. labeling the frequency axis so that it tells velocity?
In that case, the Qt GUI frequency case would be a way to go. You can
set the center frequency to do 1., it inherently does 2. and 3. can be
achieved (ignoring wrong physical unit labels) by adjusting the
bandwidth parameter.
Cheers,
Marcus