[AstroPy] fits coordinate system keyword
Paul Kuin
npkuin at gmail.com
Tue Oct 6 11:20:24 EDT 2015
Hi Tom,
Correct. I did first read then pass the header to WCS.
The way I interpret the parameter fix-False description, it seems like the
WCS header with the warning is that it will fail ? I'll give it a try
later.
Thanks, Paul
On Tue, Oct 6, 2015 at 1:15 PM, Thomas Robitaille <
thomas.robitaille at gmail.com> wrote:
> Hi Paul,
>
> As far as I'm aware, the error shouldn't be happening when you open
> the file, but when you pass the header to the WCS class from
> astropy.wcs. I think you can get rid of the warnings by simply doing
>
> wcs = WCS(header, fix=False)
>
> See
> http://docs.astropy.org/en/stable/api/astropy.wcs.WCS.html#astropy.wcs.WCS
>
> Cheers,
> Tom
>
> On 6 October 2015 at 09:15, Paul Kuin <npkuin at gmail.com> wrote:
> > It seems that WCS RADECSYS was not dropped then; it just ended up in the
> > standard in a different way. Probably to preserve backward compatibility
> to
> > old FITS files. It did throw me off, with just one letter difference! I
> > think there must be some old software that is still being used to create
> > fits files that do use RADECSYS. I was using it (not bothering to check
> > the standard all the time, - yes bad!) and I suspect that Swift UVOT
> > software uses it (which is built on the HEASARC FTOOLS - so that might
> use
> > it also). I'll bring it up in the UVOT group, but with the kind of very
> > limited software support that is left after 10 years of Swift mission, it
> > might not be possible to make the changes.
> >
> > To get back to my original issue. I think this means the WCS keywords
> are a
> > historical set that is still supported, but non-standard. I also think
> that
> > getting a warning each time a file is opened is wrong.
> >
> > In my software I'd like to disable that warning. I guess I'll need to
> have
> > a good look at the error handling in Astropy as I have somewhere another
> > warning pop up with loads of verbage, opening an ascii file. It actually
> > worked, just is very loud. I hope there is a way to get a different
> > response for errors and warnings to be used during testing and actual
> use.
> >
> > Thanks again for all the responses.
> >
> > Paul Kuin
> >
> >
> >
> > On Mon, Oct 5, 2015 at 11:03 PM, Tim Jenness <tim.jenness at gmail.com>
> wrote:
> >>
> >> RADECSYS is a very common historic header that was used before support
> was
> >> added for multiple WCS definitions in a single header. I think it was
> >> dropped before the official paper II standard was published was was
> part of
> >> the initial draft:
> >>
> >> See e.g. http://www.adass.org/adass/proceedings/adass99/P1-29/
> >>
> >> --
> >> Tim Jenness
> >>
> >> On Mon, Oct 5, 2015 at 2:47 PM, Paul Kuin <npkuin at gmail.com> wrote:
> >>>
> >>> That is so. You're absolutely right! I'm so sorry! I did not catch
> that
> >>> one.
> >>>
> >>> That is probably an error that sneeked into the FITS headers from
> Swift.
> >>> Perhaps its a Heasarc thing, but somehow I think its a bug.
> >>>
> >>> Thank you all for helping with this.
> >>>
> >>> Paul
> >>>
> >>> On Mon, Oct 5, 2015 at 10:17 PM, Thomas Robitaille
> >>> <thomas.robitaille at gmail.com> wrote:
> >>>>
> >>>> I think there is a misunderstanding:
> >>>>
> >>>> RADECSYS is not valid
> >>>>
> >>>> RADESYS is valid
> >>>>
> >>>> (note the extra C). We are not debating that RADESYS is valid - it is
> -
> >>>> but the warning concerns the common mis-spelling of RADE*C*SYS. Does
> >>>> this make sense?
> >>>>
> >>>> Cheers,
> >>>> Tom
> >>>>
> >>>> Paul Kuin wrote:
> >>>> > In the WCS II standard paper ( M. R. Calabretta and E. W. Greisen:
> >>>> > Representations of celestial coordinates in FITS
> >>>> > http://www.aanda.org/articles/aa/pdf/2002/45/aah3860.pdf) on page
> 1079
> >>>> > the is a table defining some variables used. In particular 'a' is
> >>>> > alternate version code 'blank or [A-Z]. In table 2 on page 1082, the
> >>>> > definition is RADESYSa, meaning that valid versions are either
> >>>> > RADESYS,
> >>>> > RADESYSA, RADESYSB, ... , RADESYSZ.
> >>>> >
> >>>> > So it always was defined as a valid. Similar, EQUINOXa/. I've seen
> >>>> > that
> >>>> > mostly used as just EQUINOX. If the header has just one WCS block,
> or
> >>>> > a
> >>>> > preferred one, that is useful to have.
> >>>> >
> >>>> > Let's see what Bill Pence says. Maybe there were some changes after
> >>>> > all.
> >>>> >
> >>>> >
> >>>> >
> >>>> > On Mon, Oct 5, 2015 at 8:34 PM, Thomas Robitaille
> >>>> > <thomas.robitaille at gmail.com <mailto:thomas.robitaille at gmail.com>>
> >>>> > wrote:
> >>>> >
> >>>> > Hi Paul,
> >>>> >
> >>>> > Just out of curiosity, was RADECSYS ever a keyword in the FITS
> >>>> > standard,
> >>>> > as opposed to RADESYS? (which is the currently valid keyword).
> If
> >>>> > so, in
> >>>> > what version of the standard?
> >>>> >
> >>>> > Cheers,
> >>>> > Tom
> >>>> >
> >>>> > Paul Kuin wrote:
> >>>> > > Actually, one of the basic tenets of FITS is to be completely
> >>>> > backward
> >>>> > > compatible, so any keyword that was valid in the past is valid
> >>>> > now. So
> >>>> > > that warning is also inaccurate. If it was standard, it still
> >>>> > is, and
> >>>> > > ever will be.
> >>>> > >
> >>>> > >
> >>>> > >
> >>>> > > On Mon, Oct 5, 2015 at 5:25 PM, Erik Bray <embray at stsci.edu
> >>>> > <mailto:embray at stsci.edu>
> >>>> > > <mailto:embray at stsci.edu <mailto:embray at stsci.edu>>> wrote:
> >>>> > >
> >>>> > > On 10/05/2015 12:17 PM, Paul Kuin wrote:
> >>>> > >
> >>>> > >
> >>>> > >
> >>>> > > I am getting very annoyed of the warning that keeps
> >>>> > popping up
> >>>> > >
> >>>> > > WARNING: FITSFixedWarning: RADECSYS= 'FK5' / default
> >>>> > > RADECSYS is non-standard, use RADESYSa.
> >>>> > [astropy.wcs.wcs]
> >>>> > >
> >>>> > > I'm not sure when the FITS standard changed, but MOST
> >>>> > legacy
> >>>> > > fits files (I use)
> >>>> > > will have the RADECSYS keyword. It works, and I do not
> >>>> > see why
> >>>> > > someone felt the
> >>>> > > need to keep this warning being popped up all the
> time.
> >>>> > >
> >>>> > >
> >>>> > > Probably as a warning to remind authors of new files that
> >>>> > they
> >>>> > > shouldn't be using that keyword. I don't know that it
> >>>> > necessarily
> >>>> > > needs to be displayed every time reading in a WCS except
> >>>> > maybe to
> >>>> > > head off cases of ambiguity. But I don't know this
> >>>> > particular
> >>>> > issue
> >>>> > > well enough to be sure if the warning is appropriate in
> all
> >>>> > cases or
> >>>> > > not.
> >>>> > >
> >>>> > > I think that by default it should be off.
> >>>> > >
> >>>> > > Since you all probably think it should be there, I
> would
> >>>> > like to
> >>>> > > know how to
> >>>> > > turn it off ? any suggestion on how to do that?
> >>>> > >
> >>>> > >
> >>>> > > http://docs.astropy.org/en/stable/warnings.html
> >>>> > >
> >>>> > >
> >>>> > > Erik
> >>>> > >
> >>>> > > _______________________________________________
> >>>> > > AstroPy mailing list
> >>>> > > AstroPy at scipy.org <mailto:AstroPy at scipy.org>
> >>>> > <mailto:AstroPy at scipy.org <mailto:AstroPy at scipy.org>>
> >>>> > > https://mail.scipy.org/mailman/listinfo/astropy
> >>>> > >
> >>>> > >
> >>>> > >
> >>>> > >
> >>>> > > --
> >>>> > >
> >>>> > > * * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
> >>>> > > Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk <mailto:
> n.kuin at ucl.ac.uk>
> >>>> > <mailto:n.kuin at ucl.ac.uk <mailto:n.kuin at ucl.ac.uk>>)
> >>>> > > phone +44-(0)1483 (prefix) -204927 (work)
> >>>> > > mobile +44(0)7806985366 <tel:%2B44%280%297806985366> skype
> ID:
> >>>> > npkuin
> >>>> > > Mullard Space Science Laboratory – University College
> London –
> >>>> > > Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
> >>>> > >
> >>>> > > _______________________________________________
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> >>>> >
> >>>> >
> >>>> >
> >>>> >
> >>>> > --
> >>>> >
> >>>> > * * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
> >>>> > Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk <mailto:n.kuin at ucl.ac.uk>)
> >>>> > phone +44-(0)1483 (prefix) -204927 (work)
> >>>> > mobile +44(0)7806985366 skype ID: npkuin
> >>>> > Mullard Space Science Laboratory – University College London –
> >>>> > Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
> >>>> >
> >>>> > _______________________________________________
> >>>> > AstroPy mailing list
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> >>>
> >>>
> >>>
> >>>
> >>> --
> >>>
> >>> * * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
> >>> Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk)
> >>> phone +44-(0)1483 (prefix) -204927 (work)
> >>> mobile +44(0)7806985366 skype ID: npkuin
> >>> Mullard Space Science Laboratory – University College London –
> >>> Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
> >>>
> >>> _______________________________________________
> >>> AstroPy mailing list
> >>> AstroPy at scipy.org
> >>> https://mail.scipy.org/mailman/listinfo/astropy
> >>>
> >>
> >>
> >> _______________________________________________
> >> AstroPy mailing list
> >> AstroPy at scipy.org
> >> https://mail.scipy.org/mailman/listinfo/astropy
> >>
> >
> >
> >
> > --
> >
> > * * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
> > Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk)
> > phone +44-(0)1483 (prefix) -204927 (work)
> > mobile +44(0)7806985366 skype ID: npkuin
> > Mullard Space Science Laboratory – University College London –
> > Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
> >
> > _______________________________________________
> > AstroPy mailing list
> > AstroPy at scipy.org
> > https://mail.scipy.org/mailman/listinfo/astropy
> >
> _______________________________________________
> AstroPy mailing list
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--
* * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk)
phone +44-(0)1483 (prefix) -204927 (work)
mobile +44(0)7806985366 skype ID: npkuin
Mullard Space Science Laboratory – University College London –
Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
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