Besides the eye, the astronomers use a photographic plate, bolometer, a photo-electric cell, and other instruments.
"Lectures on Stellar Statistics"
Carl Vilhelm Ludvig Charlier
"A bolometer, invented by the late Professor Langley," he replied, his attention riveted on it.
"The Exploits of Elaine"
Arthur B. Reeve
As I moved over to look at the bolometer, I happened to glance into the busybody and saw that a crowd was rapidly collecting on the sidewalk.
"The Exploits of Elaine"
Arthur B. Reeve