a135-calendar-notes

# a135-calendar-notes - Astronomy 135 Archaeoastronomy...

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Astronomy 135: Archaeoastronomy Calendar Notes Synodic month (new moon to new moon) = Synodic month = 29.5309 days (This is the month we observe and keep calendars by) Sidereal month = 27.3 days (This is the period of revolution of the moon’s orbit.) 1 Saros = 223 months = 6585.391 days = 18 years, 11 days, 8 hours Tropical solar year = 365.2422 days How many synodic months are there in a solar year? 365.2422/29.5309 = 12.3681= 12 months and 10.87 days Solar Calendars: Egyptian Civil Calendar 12 months of 30 days, 5 days outside of the normal calendar at the end. Roman Julian Calendar, 45 BCE 12 months odd months have 31 days even months have 30 days February has 29 days, except every 4 years is a leap year, when Feb. has 30 days In 8 BCE, “Sextilis” became “August” and stole a day from February 1 year = 365.25 days This year is too long compared to tropical year by 365.2422 - 365.25 = 0.0078 days = 11 minutes. The Julian year slowly creeps ahead of the true tropical year by 1 day every 128

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## This note was uploaded on 10/15/2008 for the course ASTR 135 taught by Professor Michaelfaison during the Spring '08 term at Yale.

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a135-calendar-notes - Astronomy 135 Archaeoastronomy...

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