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helical rising
The first observable rising of a celestial object late in morning twilight after conjunction with the Sun. The heliacal rising of Sirius heralded the Nile floods and marked an important point in the ancient Egyptian calendar (see Egyptian astronomy). Helical setting is the last visible setting of a celestial object in the evening sky before conjunction.
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• CELESTIAL MECHANICSAlso on this site:
Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History