[Fwd: VOTimeSeries]

[Francois Ochsenbein]

Hi Raul,

Yes this would be a good solution -- I mean to assign another name than
MJD for a time which is a nomber of days elapsed since a reference date.
DJD (differential julian date) could be a better wording than IJD.

Thanks, Francois

>
>Hello,
>
>I would like to clarify the two aspects Francois is refering.
>
>Francois Ochsenbein wrote:
>>
>> ==> in the TimeObs, the value is a number of days since TimeZero.
>>     The comment says that the value is an MJD value .
>>
>
>As said in the mail sent by Enrique, we developed the OMC SSAP service
>using the the SSAP protocol Version 0.91 and Spectrum Data Model Version
>0.95. There were a big work interpreting the two documents and trying to
>produce a service consistent with them both. For the definition of the
>time frame, three of the fields were Frame.Time.Type, which definition
>is "Time type, always equal to MJD"; Frame.Time.Zero, which definition
>is "Zero point of timescale in MJD, default 0" and
>"Coverage.Location.Time.Value", which definition is "Midpoint of
>Exposure, on JD scale". In the image sent by Roy, there is no reference
>to the utype, but if you try the last URL Enrique sent, you will get the
>actual VOTable the system returns, where:
>TimeObs = Coverage.Location.Time.Value
>TimeZero = Frame.Time.Zero = 51544.0
>
>I am not an astronomer, but my understanding was that once specified the
>Zero point, every time would be added automatically to this zero point
>to obtain the corresponding MJD, if it is not the case, please, make me
>know and I will correct it. Or maybe the problem is just with the
>comment where, maybe, would be better to say "IJD" or "JD" instead of
>"MJD"...
>
>
>
>> ==> in the VOTable, the unit part of the Time field specifies that
>>     the units are 's' (seconds). But the data values (1305.65557 etc)
>>     are most likely days elapsed since TimeZero.
>
>You are right, I have already corrected this.Thanks
>
>
>Raúl
>
>
>

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Francois Ochsenbein       ------       Observatoire Astronomique de Strasbourg
   11, rue de l'Universite F-67000 STRASBOURG       Phone: +33-(0)390 24 24 29
Email: francois at astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 32
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