Astronomy Lesson 1
Some useful astronomical facts and knowledge.
- The sun tracks around the sky at the same angular rate as the earth goes around its orbit
- Every day the same star comes to your meridian, where is the sun?
- Throughout the year the sun would go in a circle
- The vernal equinox is a fixed point on the celestial sphere. (occurs about March 1st)
- Chosen to be 0 hours of right ascension, 0 longitude.
- On the equinoxes, day and night are of equal length.
- On a certain date the meridian goes through the vernal equinox and is directly overhead at the zenith at midnight. Every day after that it takes another 4 minutes for the vernal equinox to get to the zenith position
- After 1 year the vernal equinox will intercept the zenith at Greenwich a whole day later at exactly midnight again.
- E.g. if on a certain day of the year at an observatory a star is at zenith then 6 months later that star will come through the zenith of the observatory 12 hours later.
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