Isadore Epstein (October 23, 1919 in Tallinn, Estonia – September 17, 1995 in New York City)[1] was an astronomer.
He was the first, in this connection, to recognize the importance of the opacity of matter in terms of its resistance to the flow of solar radiation, leading to the first models of the Sun to give sensible values for its energy output.
Epstein was a leader in the first modern surveys to find sites for observatories in the Southern Hemisphere.
He studied the clarity and stability of the atmosphere and accessibility of sites in Australia, South Africa, Chile, and Argentina during the 1960s.
A long term study of stellar motions was instituted there, and Argentina's national observatory was moved to the site.