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In astronomy how is image registration done? Is there some sort of astronomic dead reckoning system? Or is it just image based with some kind of Homography technique?

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Most images are registered by finding the location of known stars from a high resolution catalog such as GAIA. So you fit centroids of all stars in an image, then do a search of Gaia sources in that location and do some sort of linear or higher order polynomial mapping of pixel space to the celestial sphere reference coordinates ICRF.

Astrometry.net is a service that does an approximate version of this on the web.

I am glossing over many details here, but this is roughly what happens.

Very cool to learn about other areas of knowledge. Astrometry.net really made this quite visual thanks.

For the curious wanting to go down this rabbit hole here seems to be an ESA archive dataset of 'GAIA Data Release 3' (released 3 June 2022) :

https://cdn.gea.esac.esa.int/Gaia/gdr3/

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