Guest guest Posted November 17, 2004 Report Share Posted November 17, 2004 Here's some helpful information for anyone who's curious about the crescent moon phase: skymap , " Bamm " <bamm@a...> wrote: > > I think the data you are looking for is the " elongation " , > defined as the angle between the object and the sun. > (Technically, I think the term really refers to the > difference in ecliptic longitude between the object > and the sun.) > > Get an hourly table of the elongation of the moon, and when > it exceeds 7.5, then it is big enough to be visible. Hope > this helps. > > Bamm Bamm is correct in that elongation is the term you are looking to search on, however it is not the only facttor that will affect at what age a cresent Moon can be seen. The inclination of the Ecliptic to the local horizon plays a large role. During the late summer & fall, the ecliptic lies at a very shallow angle to the horizon at sunset, thus although the elongation of an object with relation to the Sun may be large, that object may never be high enough above the horizon in twilight to see before it sets. This is the same reason we have the " harvest moon " . During the Spring, particularly around the Vernal Equinox, the ecliptic stands almost vertical to the horizon, maximizing the effect of elongation as far as visibility goes. So essentially the best time to view a young cresent moon would be in late winter early Spring, when the a moon 7.5 degrees elogated at sunset would actually be close to 7.5 degrees above the horizon. Hope this helps. Clear Skies Rick Tejera Editor SACNews Saguaro Astronomy Club SaguaroAstro www.saguaroastro.org Quote Link to comment Share on other sites More sharing options...
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