ObsCore: o_ucd for uncalibrated data?

[Petr Skoda]

On Wed, 22 Jul 2015, Alberto Micol wrote:
>
> Dear ObsCorers,
>
> At ESO we are serving spectra very well calibrated in wavelength, but uncalibrated in flux.
> What would be the correct o_ucd value for such data?
> I cannot find a UCD that could fit… something like: phot.uncalibrated would be nice to have…
> Any idea?

Hi Alberto,

In stellar astronomy we formally describe the vertical axis as integrated 
flux in ADU or counts ....
It is in principle produced by summing all pixels values in given 
wavelength but modified by various sensitivies of detetror (flat-field 
etc) . So perhaps something like flux in counts may be used??
So UCD="phot.count"
?????


Than the problem comes with continuum normalization made by some 
pipelines. For this was already a suggestion by Mirellei for SDM

Char.FluxAxis.CalibrationStatus='NORMALIZED'
Char.FluxAxis.unit=NULL  or 'unitless'
Char.FluxAxis.ucd=phot.flux;arith.ratio;


Is there any other suggestion ?

Just my practical view for intended usage of obscore:  I am either 
interested in getting SOME form of spectra of my object - so I am 
perfectly happy with the RAW extracted spectrum - in counts (or ADUs) or 
in a SPECIFIC form for analysis - than I prefer the FLUXCALIB=normalized 
or ABSOLUTE - if I already know about many spectra of the same object in 
given form. But more flexible approarch is to use DataLink.


OTOH - it is not sometimes obvious the spectra are normalized to 
continum without visual inspection - you see the most values are at level 
1.0 and there is not visible skew of the spectra ....

BTW - I am glad that the ESO is still considering the VO as a viable 
technology for presenting data ....

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*  Petr Skoda                         Phone : +420-323-649201, ext. 361 *
*  Stellar Department                         +420-323-620361           *
*  Astronomical Institute AS CR       Fax   : +420-323-620250           *
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