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Question
Why, at certain times does the moon appear to be larger than other times? Does it have anything to do with dust or amount of atmosphere you look through?
Hello,
When an astronomical object is on the horizon at rising or setting, the numerical value of the refraction suffered is about 34' or 34 minutes of arc. This is just over a half -degree. The refractive effect is a direct result of the thickness of the atmosphere through which one observes.
For the case of the full Moon, this effect combined with the tendency of the typical human eye to see an object *near the horizon* as larger - will, in effect, make the Moon *seem* larger. (Though I have known some folks, including my wife, who are not the least fooled by this effect!)
I don't think that dust in the atmosphere will make that much difference to the apparent *size* though it may well make the Moon appear with a darker hue.
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Answers by Expert:
Philip Stahl
Expertise
I have forty years of experience in Astronomy, specifically solar and space physics. My specialties include the physics of solar flares, sunspots, including their effects on Earth and statistics as applied to astronomical investigations.
Experience
Astronomy: more than forty years experience starting with construction of my own simple telescopes. Worked at university observatory in college, doing astrographic measurements. M.Phil. degree in Physics/Solar Physics and more than ten years as researcher.
Organizations
American Astronomical Society (Solar Physics and Dynamical Astronomy divisions), American Mathematical Society, American Geophysical Union
Publications
Solar Physics (journal), The Journal of the Royal Astronomical Society of Canada, The Proceedings of the Meudon Solar Flare Workshop (1986), The Proceedings of the Caribbean Physics Conference (1985). Books: 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level'.
Education/Credentials
B.A. Astronomy, M. Phil. Physics
Awards and Honors
American Astronomical Society Studentship Award (1984), Barbados Government Award for Solar Research
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