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ERIC Number: EJ1002774
Record Type: Journal
Publication Date: 2012-Sep
Pages: 4
Abstractor: As Provided
Reference Count: 4
ISSN: ISSN-0031-9120
Measuring the Apparent Size of the Moon with a Digital Camera
Ellery, Adam; Hughes, Stephen
Physics Education, v47 n5 p616-619 Sep 2012
The Moon appears to be much larger closer to the horizon than when higher in the sky. This is called the "Moon illusion" since the observed size of the Moon is not actually larger when the Moon is just above the horizon. This paper describes a technique for verifying that the observed size of the Moon is not larger on the horizon. The technique can be performed easily in a high-school teaching environment. Moreover, the technique demonstrates the surprising fact that the observed size of the Moon is actually smaller on the horizon due to atmospheric refraction. For the purposes of this paper, several images of the Moon were taken with it close to the horizon and close to the zenith. The images were processed using a free program called ImageJ. The Moon was found to be 5.73 [plus or minus] 0.04% smaller in area on the horizon then at the zenith. (Contains 4 figures.)
Institute of Physics Publishing. The Public Ledger Building Suite 929, 150 South Independence Mall West, Philadelphia, PA 19106. Tel: 215-627-0880; Fax: 215-627-0879; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: High Schools
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A