Blink Comparator
Tombaughs task was to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. Using a machine called a blink comparator
Historical biography archive · Updated 2026-11-03
Clyde Tombaugh Biography and Timeline
Follow Clyde Tombaugh through 8 dated historical records for United States of America.
Clyde Tombaugh, historical timeline
A chronological timeline drawn from matching World History Database records.
8Distinct records
1 of 1Page
1929–1930Years on this page
1929
Discovery of Planet X
The search for Planet X resumes when the Lowell Observatory director, Vesto Melvin Slipher, summarily hands the job of locating Planet X to Clyde Tombaugh
Discovery of Pluto
Tombaugh is assigned to systematically photograph the night sky and compare paired plates with a blink comparator in the renewed search for Planet X.
1930
Discovery of Pluto
Tombaugh exposes one of the photographic plates later used, with the January 29 plate, to identify Pluto's motion.
Discovery of Pluto
Tombaugh exposes the second of the two photographic plates later used to identify Pluto's motion against background stars.
Discovery of Pluto
Tombaugh identifies Pluto as a moving object while comparing photographic plates taken on January 23 and January 29.
Discovery of Pluto
Using a blink comparator, Tombaugh identifies a moving object on plates taken January 23 and January 29, discovering Pluto.
Discovery of Pluto
News of Pluto's discovery is telegraphed from Lowell Observatory to the Harvard College Observatory.
Records, sources and methodology
These dates and descriptions come from the historical_events database. Exact duplicate records have been collapsed. Names are grouped by the country, Name 2 and Name 1 fields; records with missing Name 2 cannot be reliably assigned to an individual biography. Check the underlying sources before formal citation.