Allan Rex Sandage (June 18, 1926 – November 13, 2010) was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He determined the first reasonably accurate values for the Hubble constant and the age of the universe. Clyde William Tombaugh ( February 4, 1906 – January 17, 1997) was an American astronomer. He discovered Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper belt. At the time of discovery, Pluto was considered a planet but was later reclassified as a dwarf planet in 2006. Tombaugh also discovered many asteroids.
Sandage has signed and inscribed an index card. Tombaugh has signed first day of issue envelope Palomar Mountain Observatory post card. Postmarked Aug 30, 1948.