Tell Time by the Big Dipper Constellation

If you don’t have or can’t afford a watch, you could still tell time at night. To use the Big Dipper star clusters in telling time (by the line from the pointer stars to Polaris) is not really that hard.

Big Dipper clock face


  • It’s a counter-clockwise running 24-hour clock,  because the earth rotates west to east a full turn every 24 hours, and
  • It turns fast.  Due to the earth’s annual orbit around the sun, it gains 24 hours every year.

So to use the clock you only need to remember two things. 

  • Memorize the 24-hour clock face, shown above, and
  • Adjust the 24-hour or midnight mark on the clock to the current date.  24 hours in 12 months is two hours every month, so shift the midnight mark up by two hours (counter-clockwise) on the clock face each month, or a half-hour each week.  Some key dates to remember are shown on the drawing above.


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