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Hi
Here's one you or anyone can do - Measuring the Sidereal Day (day using stars as opposed to a Mean Solar day of 24 hours). The Sidereal Day is only 23 hours, 56 minutes and 4 seconds.
You need a tall building, preferrably with a straight vertical edge and a star (or group of stars) that passes behind the building or object. You will also need to use the same location to observe the star from as it passes behind the building. Obviously a good digital watch that shows HH:MM:SS is a good bet for timing the disappearance.
Over a few weeks or months, go out on as many nights that you can and note the time in Hours Minutes and Seconds that the chosen star(s) disappears from view behind the building. Do your best adopt the same pose when you observe the star. Record your times.
Plot your times on a graph with days along one axis and times along the other. What you will note is that the star appears to disappear a few minutes earlier than the previous night. This is because the Sidereal Day is shorter than our 24 hour day by a few minutes. Draw the best line through the points on the graph to work out the Mean Sidereal day. You will get slightly different results to friends, but you should all be in the same ball park of a few minutes shorter than the Mean Solar Day.
All the best!
Pete
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