It is a commonly held belief that the Moon appears larger near the horizon as a result of some kind of magnification effect caused by the Earth's atmosphere. This is not true, although the atmosphere does change the colour of the Moon. Actually, the measured optical angle of the Moon's vertical diameter is smaller for the horizon moon than for the zenith moon, so when the rising moon is on the horizon it appears (both visually and in photographs) to be a bit squashed down (ovoid). 
(source:wikipedia)

Fujifilf finepix E550, S/W 8" - afocally, Left photo:, 22/01/2008 - 18:02, shutter speed 1/80, Aperture Value 2.8, ISO 200, Right photo:, 23/01/2008 - 02:01, shutter speed 1/800, Aperture Value 2.8, ISO 80