AST101L5 - Astronomy 101 Online: Retrograde Motion...

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Astronomy 101 Online: Retrograde Motion Retrograde motion is the apparent backward motion of the planets in the night sky. As you watch the planets move through the background stars, you'll find that they generally travel in the same direction as the sun - from west to east or counter-clockwise. However, there are times when the planets appear to stop, change their direction for a short while, before stopping again to resume their normal course through the sky. This is the period of retrograde motion for the planet. In this project, you'll be using the Starry Night Enthusiast program to watch the retrograde motion of several of the planets, paying particular attention to the retrograde motion of the planet Mars. Start by opening up Starry Night. Under the "View" menu, select the "Hide Daylight" option. Open up the Options tab on the left edge of the screen (not the Options menu at the top of the screen). Select "Local View" and turn off the "Local Horizon (flat)". You should now have a view of the entire night sky, without ever having to worry about the ground blocking your view. We'll start by looking at which of the planets undergoes retrograde motion. Start by finding and centering on the sun. Since Mercury and Venus are closer to the sun than Earth, they never stray far from the sun in the sky. Set the time step to 1 day and run time forward for roughly 6 months of time. 1)
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This note was uploaded on 10/06/2008 for the course ASTRO 100 taught by Professor Kaler during the Fall '08 term at University of Illinois at Urbana–Champaign.

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AST101L5 - Astronomy 101 Online: Retrograde Motion...

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