History and Astronomical Significance of Halloween


Halloween (October 31), along with All-Saints Day (November 1) and All-Souls Day (November 2), marks the approximate midway point between the Autumnal Equinox (the astronomical beginning of the season of Autumn or Fall: ~September 22) and the Winter Solstice (the beginning of Winter: ~December 21).


As such, Halloween is considered a traditional “cross-quarter day,” the day that crosses the seasonal quarter from the first half of Autumn to the second half of Autumn. Halloween is probably the best known of the four cross-quarter days each year. Other traditional cross-quarter days occur on February 2 (better known as Groundhog Day), May 1 (better known as May Day), and August 1.


The celebration of Halloween began in the 5th century B.C. with the Celtic peoples of Ireland, who called the day Samhain. In A.D. 835, the Catholic Church named November 1 All-Saints Day, and the previous day, October 31 became “All-Hallows’ Eve” or  Halloween, the eve or evening before All-Saints Day.


And, each Halloween at about Midnight, if the sky is clear, you can see the Pleiades star cluster (also known as the Seven Sisters) almost directly overhead.




Friends of the Zeiss

P.O. Box 1041                                                                             

Pittsburgh, Pennsylvania 15230-1041 U.S.A.

Telephone: 412-561-7876

Electronic Mail: < friendsofthezeiss@planetarium.cc >

Internet Web Site: < http://www.friendsofthezeiss.org >


Promoting preservation and restoration of the historic building, equipment and artifacts of Pittsburgh’s original Buhl Planetarium and Institute of Popular Science. This includes the historic Zeiss II Planetarium Projector, which, prior to dismantling in 2002, was the oldest operable major planetarium projector in the world ! To learn more about the history of Buhl Planetarium, go to this Internet web site:

< http://www.planetarium.cc >.