I already asked this question in the Astronomy community, but there it was recommended to me to also try my luck here.
I would like to know the original description of point sources and point spread functions. They are well-known concepts (in particular in astronomy e.g.), but every source that I could find so far that discusses them doesn't mention who actually discovered or came up with them.
The closest thing that I found for now is the work by Airy, who mathematically described the diffraction pattern generated by a perfect optical system. So I guess that is very close. However, according to the wiki article, the phenomenon was described by Herschel at least seven years prior. But that is just regarding the outer rings of the diffraction pattern. So I would guess astronomers must have been aware of the blob-like appearance of poin sources even earlier.