This subject is treated in the article Photometry, Celestial.
He was elected a fellow of the Royal Society in 1840, and in 1892 was awarded one of the royal medals for his work on photometry and stellar parallax.
In 1882 Pritchard commenced a systematic study of stellar photometry.
He found the light of the sun to be 300 times more intense than that of the moon, and thus made some of the earliest measurements in photometry.
It has thus come about that astrophysics owes its recent development, and its recognition as a distinct branch of astronomical science, to the combination of the processes involved in the three arts of spectroscopy, photography and photometry.