[AstroPy] Compute approximate WCS for a given wide-field photo

[Christoph Deil]

Hi,

I’d like to make some images that combine a normal photo with an astronomical survey image, as in this example:
https://de.wikipedia.org/wiki/High_Energy_Stereoscopic_System#/media/File:HESS-Gammastrahlungsquellen_Montage.jpg <https://de.wikipedia.org/wiki/High_Energy_Stereoscopic_System#/media/File:HESS-Gammastrahlungsquellen_Montage.jpg>

I know about http://reproject.readthedocs.io <http://reproject.readthedocs.io/>, but to use it I need a WCS for the photo.

Let’s assume I know the sky position of a few pixels in the photo already (from star finding or by hand).

How can I get an approximate WCS for the photo?

Is there some projection that roughly matches what wide-field (non-astronomical, hand-held, covering ~ 50 deg on the sky) photo cameras do?
I presume the projection reference point should always be at the centre of the image?
Can the pixel scale parameters can be computed from EXIF meta information in the photo?

Is there a good web page with a description, or even a Python package that will help me compute the WCS?

Or is the whole approach of trying to go via a WCS transform for the photo not a great idea, and some other transform should be used?

Any tips would be appreciated!

— Christoph

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