[AstroPy] TAN--SIP -> TAN PV WCS projection conversion

[Octavi Fors]

Hi Guang,

I understand that wcs-resample requires a second (target) image file with
the WCS you want to apply to the input image, which has different WCS
projection.

In my case, I only have one image with TAN--SIP projection (which
SExtractor doesn't seem to understand), and my aim is to get an output
image with the TAN PV_i_j projection (which is of one the projections
SExtractor understands).

Thanks,

Octavi.



On Thu, Jul 24, 2014 at 10:33 PM, Guang Yang <yg1991 at mail.ustc.edu.cn>
wrote:

> Hi Octavi,
>
> The astrometry.net group has some related codes. (
> http://astrometry.net/doc/readme.html#fits-utilities ) You may try
> wcs-resample in them, But I'm not sure it works for your case.
>
> Are you trying to correct astrometry of an image so that it matches well
> with another? If so, we can discuss this, since that's what I did last year.
>
> Thanks,
> Guang
>
>
> -----Original email-----
> *From:* "Octavi Fors" <octavi at live.unc.edu>
> *Sent Time:* Jul 25, 2014 7:47:11 AM
> *To:* astropy at scipy.org
> *Cc:*
> *Subject:* [AstroPy] TAN--SIP -> TAN PV WCS projection conversion
>
>
> Dear all,
>
> I've been struggling with this for two weeks ago, but no luck so far.
>
> I'm getting the astrometry plate solution of images from a 40ºx40º FoV
> camera-lens CCD with Astrometry.net 0.49, TAN--SIP projection, and *5th*
> order SIP distortion polynomials.
>
> If I overplot with ds9 the Tycho2 stars in the field in J2000 coordinates
> (Analysis->Catalogs->Optical->Tycho2 menu), the green circles match the
> positions of all the stars in the FoV.
>
> *However*, after running SExtractor 2.19.5 over the plate solved image,
> while the pixel coordinates (XWIN_IMAGE,YWIN_IMAGE) *do* match the stars,
> the precessed celestial (ALPHAWIN_J2000,DELTAWIN_J2000) ones *do not* (they
> show offsets of several arcmins).
>
> I've asked SExtractor developers if such software does support TAN--SIP
> WCS convertion. Still waiting, but my guess is it does not.
>
> So a TAN--SIP->TAN-PV projection converter is what I'm looking for.
>
> Caltech PTF team (see SPIE paper
> <http://web.ipac.caltech.edu/staff/shupe/reprints/SIP_to_PV_SPIE2012.pdf>)
> made these SIP<->PV converters to 4th order (not to 5th order, which is
> what I need). For license issues, they can only release the binaries here
> <http://data.astrometry.net/pv2sip-binaries-intel/> , but not the source
> code (which would allow me to extend the conversion formulas to 5th order).
>
> Is there anybody in astropy community who is planning to implement a
> method in WCS class for converting from SIP to PV projection?
> I would be more than happy to provide testing images.
>
> Thanks in advance,
>
> Octavi.
>
> --
> Octavi Fors
> Postdoctoral Research Associate
> Department of Physics and Astronomy
> The University of North Carolina at Chapel Hill
> CB #3255, #157 Phillips Hall
> Chapel Hill, NC 27599
>
>
>
> _______________________________________________
> AstroPy mailing list
> AstroPy at scipy.org
> http://mail.scipy.org/mailman/listinfo/astropy
>
>


-- 
Octavi Fors
Postdoctoral Research Associate
Department of Physics and Astronomy
The University of North Carolina at Chapel Hill
CB #3255, #157 Phillips Hall
Chapel Hill, NC 27599
Office: (919) 962-3606
Fax:    (919) 962-0480
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