[obs-tap]observable quantities in observations and their UCDs

[Anita M. S. Richards]

>
> As I already mentioned in our discussion here at CDS, I do not think that 
> "velocity" is observable in any sense. I would agree that it can be a 
> spectral coordinate, but we NEVER directly observe velocities. Velocities are 
> results of the [model-dependent] data analysis.
>
> With best regards,
> 						Igor

Hm, but what about proper motions?

Anita