Equipped with a home-made astrolabe and Kepler's laws, one can arrive at accurate estimates of the orbits of planets. Over the past three years, I have used an astrolabe to collect sightings of celestial bodies visible from my backyard. This paper shows that it is possible to measure one's latitude and longitude, the current time, locations of celestial bodies, and the sizes of the orbits of nearby planets. When the astrolabe is used to collect both daytime and nighttime observations of Venus, one can also demonstrate that Venus orbits the Sun.
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