Archived posting to the Leica Users Group, 1999/12/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Original messages, in part: <<<<<<<< The moon probably has close approaches to the earth at different times ofthe year andthese close approaches occur at different parts of the world. The large apparent size of the moon, like the occasional sunset where the object seems to be largeer than normal is due to a phenomena related to "optical lensing" in the atmosphere. The object viewed at the horizon is seen as it passes through the greatest layer of atmosphere (from the viewers perspective). The atmosphere acts like a lens and magnifies the object's size......... - ------- The moon seems larger at the horizon as we can compare it to familiar reference points: buildings, trees, cows... High in the sky, without reference points, it seems to shrink. This is a psychological/optical illusion that is easily verified by using your thumb at the end of your extend arm as a reference point. Try covering the moon with your thumb when the moon is low in the sky and when it is at its zenith. Alas, how life's illusions fall away. John Collier <<<<<<<<<<<<<< The moon CERTAINLY has close approaches to the earth at different times ofthe year (remenber Keller's laws) but the (relative) small difference has not significant effect on its size (at least with 35 mm photo or naked eye observation). I completely agree with the explanation of John .... and the advice of Ted saying it's better to shoot when the moon is not too much far away the horizon, at least for an esthetic approach - it's easier to include in the landscape with a small tele. But when the moon is high in sky, the picture is sharper (less atmosphere, less difraction, less smog, less dust and so on) when you use a long tele for astronomical purpose (the moon is brighter so exposure time is shorter - less vibration and so on) Bernard bernard.degaute@village.uunet.be