[Dachs-support] Assistance Required for SSAP Service Issue
Markus Demleitner
msdemlei at ari.uni-heidelberg.de
Wed Jun 5 10:56:01 CEST 2024
Hi Ildana,
On Mon, Jun 03, 2024 at 04:44:13PM +0500, Ildana Izmailova wrote:
> I tried to register at
> https://lists.g-vo.org/cgi-bin/mailman/listinfo/dachs-users to write to
> Dachs-support, but I seem to be having trouble... I haven't received any
You're at the right list; dachs-users is just release announcements.
> I'm writing to you regarding an issue with the SSAP service. We have
> published spectral images in FITS format, not in the wavelength-flux
For folks just following this thread: "FITS format" here means that
it's the raw exposures, with the spectrum and the calibrators in a 2D
image, *not* anything like SDM in FITS or the SDSS-style 1D images.
Incidentally, if anyone can recommend software for generating nice,
wavelength-calibrated spectra from that kind of thing, that would
certainly be interesting (because I don't know of anything publicly
available outside of IRAF or MIDAS).
> Currently, my question concerns the search functionality on the web service
> (https://dachs.fai.kz/spectra_agn_archive/q/web/form). When I perform a
> search by coordinates, the service responds with "Your query did not match
> any data," even though there is definitely data within the specified search
> radius. I don't understand how to fix this and have tried several different
> approaches. The headers of the frames are correctly populated with
> coordinate data in degrees, so I believe the issue is not with the headers.
> Could you please advise on how to resolve this issue?
The problem is that you are (correctly) saying:
<condDesc buildFrom="ssa_location"/>
but then, in the rowmaker, only fill the target_ra/target_dec; thus,
I'd predict that
SELECT ssa_location FROM spectra_agn_archive.raw_data
will only return NULLs, and hence any condition against that column
will always be false (and the result set empty).
Looking at the tutorial chapter on SSA, this should perhaps be made a
bit clearer: to fill ssa_location, you have fill the column,
preferably using the //ssap#fill-plainlocation apply (it's in the
template). In your case, I suppose you'd have something like this in
the rowmaker:
<apply procDef="//ssap#fill-plainlocation">
<bind key="ra">@RA_DEG</bind>
<bind key="dec">@DEC_DEG</bind>
<bind key="aperture">0.001</bind> (or whatever a sensible
estimate is)
</apply>
Also note that SSAP has two positions: ssa_location is where the
telescope was pointed, but there's also ssa_targetpos, which gives
the location of the target object. In general, they would largely be
identical, and so I'm not aware of any services that do something
sensible with ssa_targetpos. Anyway, the position DaCHS SSAP
services work against is ssa_location, and I think you can drop your
target_ra and target_dec columns without impacting anything
negatively.
Incidentally, on the ssap service, I'm pretty sure your
<condDesc>
<inputKey name="POS" ucd="pos.eq" xtype="adql:POINT"/>
</condDesc>
will actually break things, as there is no database column POS this
could work against; so, I'd say just drop it -- or am I being dumb
and this actually does something useful?
Thanks,
Markus
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