relative fluxes

[Douglas Tody]

Hi Guys -

Having a multiplicity of formats would be a problem as well.  I would
prefer to encourage client apps to update to the more powerful Spectrum
DM and its formats now that we have this.  We can down-convert on a
case by case basis to support legacy apps if necessary, but with the
introduction of the VO why not try to move to another level.

We can address the data provider issue with service frameworks.
If a data provider has a lot of spectra in 1D image format, lets add
support to a service framework (we could do this in the VAO DALServer
framework for example), and get those spectra up via SSA.  What major
spectral archives do we have that would benefit from such support?

 	- Doug


On Fri, 26 Jun 2009, Petr Skoda wrote:

>
> Good hit !!
>
> I am glad that this question is coming again. I consider this the most 
> critical issue for easy conversion of ground based optical archives.
> The rejection of opening 1D FITS in VOSpec is one of the  obstacle for 
> optical astronomers but no one wants to hear that !
> In fact it prevented me to use ESA SSA server and only with collaboration 
> with Phillipe Prugniel (who has on-the-fly 1D FITS  to BINTABLE convertor as 
> part of Pleinpot pipeline) I could finally see my spectra in VOSPEC. (it took 
> 2 years to notice this)
>
>> One example that comes to mind is that ground based spectra are very often
>> published using a 1D image FITS format, where the 1 axis is the wavelength
>> (using CDELT1, CRVAL1, CPIX1 to specify the wavelength wcs).
>
>> That format is NOT supported by the SSA, and that might cause indeed
>> problems to the ground based data providers. Sure, they could translate
>> FITS files on the fly, but we shall not forget that data providers have 
>> many other
>> things to do than try to twist their data into the VO.
>
> Another issue - there is no simple tool for the conversion of 1D FITS to 
> BINTABLE so its now easy to make archive for VOSpec consumption.
>
> Just looking at any 
>> registry
>> the number of space-based SSA services greatly outnumber the ground-based 
>> ones
>> At the level of about 90 vs 10 (or worse).
>
> And still some are giving strange outputs...
>
>
>
>
> The one I stated is certainly not 
>> the only reason
>> for this (calibrating a ground-based spectrum is much more difficult), but 
>> the format problem
>> exists (and I can tell, now that I work for a grond base archive!)
>
> YES !!!  Many smaller observatories would be eager to publish spectra in VO 
> and they have already web based archives but the spectra should be used as 
> they are.
>
> The 1D FITS is the format where all astronomers know how to get it (e.g. from 
> IRAF or MIDAS) in worst case over ASCII tables - but its is what they are 
> forced to do every day. But I have met only about 10% of stellar astronomers 
> who know what is BINTABLE FITS.
>
> Petr
>
> *************************************************************************
> *  Petr Skoda                         Phone : +420-323-649201, ext. 361 * * 
> Stellar Department                         +420-323-620361           *
> *  Astronomical Institute AS CR       Fax   : +420-323-620250           *
> *  251 65 Ondrejov                    e-mail: skoda at sunstel.asu.cas.cz  *
> *  Czech Republic                                                       *
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>