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How are sunrise, sunset, moon rise and moonset defined?
Looking at various websites that cite sunrise and set times had me wondering what is the official definition of"sun rise" or "sun set" etc??? (Likewise for the moon)
Is it defined by assuming you are on a flat plane with unobstructed horizon? Does the full disc have to be above the horizon to be "risen" or only part of the disc?? I was hoping a met guy or savvy pilot may have the answer. This question in no way indicates I have too much time on my hands...honest |
Colonial ideas on the subject. :)
It could be that the UK definitions are similar. Sunrise and sunset conventionally refer to the times when the upper edge of the disk of the Sun is on the horizon, considered unobstructed relative to the location of interest. Atmospheric conditions are assumed to be average, and the location is in a level region on the Earth's surface. Moonrise and moonset times are computed for exactly the same circumstances as for sunrise and sunset. However, moonrise and moonset may occur at any time during a 24 hour period and, consequently, it is often possible for the Moon to be seen during daylight, and to have moonless nights. It is also possible that a moonrise or moonset does not occur relative to a specific place on a given date. |
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