1.1 About units and UCDs

Though there's a heavy struggle in the Virtual Observatory Community to cover all kinds of astronomical data with a convenient model that supports a heuristic and automatic unit recognition and conversion feature, no such unit conversion software is currently available.

Spectrum Services are able to store spectra with flux values in any unit, but no interpretation of the unit strings is implemented. Thus, when calling scientific function (ie. continuum fitting), always specify values in the following units:

• Wavelength: A (Angtroms)
• Flux density: 10^-17 erg cm^-2 s^-1 A^-1
• Flux: 10^-17 erg cm^-2 s^-1
• Ra, Dec: degrees in decimal format
• Search radius: arcmins in decimal format

UCDs are designed to describe physical quantities in data models. ***