Sunday, May 13, 2012

Tell Time looking at sky in the night



Time in the Sky: Start at Polaris (http://www.ehow.com/how_2050323_find-polaris.html) and treat it as center. The up direction is for 12:00. Now to find hand, first locate the Big Dipper (http://www.ehow.com/how_17659_locate-big-little.html). Then draw a line through the two stars that are farthest away from the Big Dipper’s handle. The line passes through Polaris, that’s your “hour” hand. Now you can read the time in the sky.
The hour hand in the sky completes a full rotation in about 24 hours. So if you stare at the sky long enough, you can estimate the time you were staring. One more thing, the hand in the sky clock is twice as slow as the hour hand, and it turns counter-clockwise. So you need to double the difference of starting instance and ending instance.
Years in the Sky: To estimate the absolute time, we have to change for the day in the year. A year has twelve months and a clock has twelve hours. You can treat each month as one hour. In addition as a month has about 30 days and an hour has exactly 60 minutes, we should count a day as two minutes. Thus, February 15 is 2:30.
Fact: On March 7th at midnight the clock in the sky shows 12:00. March 7th corresponds to 3:15. So to calculate the solar time you have to add up the time on sky clock and the time on year clock and double it, Subtract the result from 6:30, which is twice 3:15, you get the solar time.
You may have to account for daylight savings time or other peculiarities of your time zone.
Woohooo you are ready to roll!

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