[AstroPy] Astroquery Using Vizier: How Do I Retrieve SDSS Photo Object Attribute "flags"? (Adam Ginsburg)

[Adam Ginsburg]

Set vizier.ROW_LIMIT = 5000.  You can also do `Vizier(row_limit=5000,
columns=['**']).query...`, iirc.

On Sat, Jul 25, 2020 at 8:19 PM Robert Carr <rspencercarr at gmail.com> wrote:

> Thank you, Prof Ginsburg.  Your advice was very helpful.  It was good to
> know that the flags were accessible.  The tweak worked fine on a standalone
> basis but within my code perhaps it hit another constraint.
>
> When I run    *calibrators = Vizier.query_region(coord.SkyCoord(ra=TRA,
> dec=TDEC, unit=(u.deg, u.deg),frame='icrs'), radius=field_of_view * u.deg,
> catalog = 'SDSS12')*
> I get 3361 calibrators for my parameters, which I subsequently whittle down
>
> When I run    *calibrators =
> Vizier(columns=['**']).query_region(coord.SkyCoord(ra=TRA, dec=TDEC,
> unit=(u.deg, u.deg),frame='icrs'), radius=field_of_view * u.deg, catalog =
> 'SDSS12') *
> I get only 50 calibrators for my parameters, which leaves me with nothing
> to whittle!
>
> Am I running afoul of a constraint?  Vizier pulls down 23 default columns
> and there are 140 or so total, so the cut seems a bit too dramatic.  If I
> am hitting a constraint, I will need to specify each of my columns up front.
>
> Thanks again,
>
> Bob C.
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 21 Jul 2020 10:44:16 -0400
> From: Adam Ginsburg <adam.g.ginsburg at gmail.com>
> To: Astronomical Python mailing list <astropy at python.org>
> Subject: Re: [AstroPy] Astroquery Using Vizier: How Do I Retrieve SDSS
>         Photo Object Attribute "flags"?
> Message-ID:
>         <CAEBNSwbh1HEbsz3mRSVBFN0dq=
> BCfUV2+o6VOmwaAm_zCjaCRA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> If you want to include additional columns in vizier queries, follow these
> instructions:
>
> https://astroquery.readthedocs.io/en/latest/vizier/vizier.html#specifying-keywords-output-columns-and-constraints-on-columns
>
>
> for example, to get *all* columns, you would do:
> Vizier(columns=["**"]).query_region(coordinates.SkyCoord(180*u.deg,
> 0*u.deg, frame='fk5'), radius=field_of_view * u.deg, catalog = 'SDSS12')
> note the double-asterisks
>
> On Tue, Jul 21, 2020 at 10:30 AM Robert Carr <rspencercarr at gmail.com>
> wrote:
>
> > I hope that this question is "in bounds," Astroquery being an Astropy
>  affiliated
> > package.
> >
> > I am querying the SDSS-12 catalog for photometric data using Vizier.  The
> > SDSS field "flags" would be ideal to help me assess the photometric
> quality
> > of the SDSS measurements for each object: this field includes a
> hexadecimal
> > code that captures issues with the photometry such as pixel saturation,
> > etc.
> >
> > My query line is:
> >         targetobj = Vizier.query_region(STAR_NAME, radius=field_of_view *
> > u.deg, catalog = 'SDSS12')
> >
> > The line in my code to collect 'flags' does not work (where
> > targetobjresults is my results from querying SDSS):
> >
> > targetobjresults.append({'flags': targetobj[0]['flags'][0]})
> >
> >
> > I receive the following error message, which I have discovered is
> because Vizier
> > returns only 23 columns of the SDSS data.
> >          Traceback (most recent call last):
> >
> >   File "<stdin>", line 32, in <module>
> >
> >   File
> >
> "C:\Users\mawgui\AppData\Local\Programs\Python\Python36\lib\site-packages\
> > astropy\table\table.py", line 1222, in __getitem__
> >
> >     return self.columns[item]
> >
> >   File
> >
> "C:\Users\mawgui\AppData\Local\Programs\Python\Python36\lib\site-packages\
> > astropy\table\table.py", line 106, in __getitem__
> >
> >     return OrderedDict.__getitem__(self, item)
> >
> > KeyError: 'flags'
> >
> >
> > Is there a way to query SDSS through Vizier to get the hexadecimal
> 'flags'
> > for each object?  Or is there another workaround?  I appreciate guidance
> on
> > how to make this happen.
> >
> > Thank you!
> >
> > Bob C
>
>
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-- 
Adam Ginsburg
Assistant Professor, Department of Astronomy
University of Florida, Gainesville
http://www.adamgginsburg.com/
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