<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi,<div class=""><br class=""></div><div class="">I’d like to make some images that combine a normal photo with an astronomical survey image, as in this example:</div><div class=""><a href="https://de.wikipedia.org/wiki/High_Energy_Stereoscopic_System#/media/File:HESS-Gammastrahlungsquellen_Montage.jpg" class="">https://de.wikipedia.org/wiki/High_Energy_Stereoscopic_System#/media/File:HESS-Gammastrahlungsquellen_Montage.jpg</a></div><div class=""><br class=""></div><div class="">I know about <a href="http://reproject.readthedocs.io" class="">http://reproject.readthedocs.io</a>, but to use it I need a WCS for the photo.</div><div class=""><br class=""></div><div class="">Let’s assume I know the sky position of a few pixels in the photo already (from star finding or by hand).</div><div class=""><br class=""></div><div class="">How can I get an approximate WCS for the photo?</div><div class=""><br class=""></div><div class="">Is there some projection that roughly matches what wide-field (non-astronomical, hand-held, covering ~ 50 deg on the sky) photo cameras do?</div><div class="">I presume the projection reference point should always be at the centre of the image?</div><div class="">Can the pixel scale parameters can be computed from EXIF meta information in the photo?</div><div class=""><br class=""></div><div class="">Is there a good web page with a description, or even a Python package that will help me compute the WCS?</div><div class=""><br class=""></div><div class="">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?</div><div class=""><br class=""></div><div class="">Any tips would be appreciated!</div><div class=""><br class=""></div><div class="">— Christoph</div><div class=""><br class=""></div></body></html>