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I need to perform accurate pixel to world coordinate transformations on FITS files that were originally created using Maxim DL. Maxim uses Pinpoint for plate solving which generates TRi_j distortion coefficients. These are incompatible with the astropy.wcs coordinate transformation functions which I was proposing to use as these assume SIP distortion coefficients.

I'm therefore looking for options to re-platesolve the FITS files to generate SIP coefficients.

So far all I've found is astrometry.net but this is an on-line service. I'm really looking for offline platesolving (preferably against a local copy of the GSC) that I can perform synchronously as part of my app's workflow.

Are there any Astropy-affiliated (or other) Python packages that perform SIP-compatible platesolving against the GSC?

Alternatively, are there any equivalents to wcs.all_pix2world that can use TRi_j distortion coefficients so I can work with the Maxim DL data?

Many thanks

Nigel

nakb
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2 Answers2

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In addition to SIP coefficients, the astropy.wcs methods will work with TPV distortion coefficients. This means you can use the output of the SCAMP astrometric solver directly with astropy.wcs. If you wish to convert TPV coefficients to the SIP form, you can use the sip_tpv package for which I am the lead contributor. I don't know of a Python package wrapping SCAMP -- I have wrapped it for the Zwicky Transient Facility pipeline but that code is not public.

user1795553
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You could do:

from astropy.io import fits
from astropy.wcs import WCS

hdul = fits.open(fitsfilename)[0]

wcs = WCS(hdul.header)

ax = fig.gca()
ax.scatter([34], [3.2], transform=ax.get_transform('world'))

(Based on this Q.)

zabop
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