ASTR 1101 Lecture Notes - Lecture 2: Retrograde And Prograde Motion, Equant, Semi-Major And Semi-Minor Axes
20 Sep 2017
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For project orbital radius = semi-major axis. The light shone straight down on different days in each city. Hipparchus o o o o o o o . Created a scale to designate the brightness of stars (1 brightest 6 the dimmest that can be seen with the naked eye) 14 000 years the north star will be vega and the seasons will change, in 26 000 years polaris will be north star again. Long term motion; drift slowly eastward around inside of celestial sphere (mercury, venus, mars, jupiter, saturn) Drift slowly westward for a few weeks or months. Ie; moving forwards, then backwards back to beginning o . Planet moves at constant speed around the epicycle. Retrograde motion is a combination of constant speed in a circular motion of epicycle and deferent. They placed they equant at the same distance the earth was from the side, center of equant moves at pace of epicycle (diagram)
