1. Celestial Navigation How to determine latitude and longitude using the stars!

2. Celestial Navigation The stars in the sky can aid you in finding your latitude and longitude. The North Star (Polaris) can help you find your latitude (but only in the Northern hemisphere…why?) The Sun can help you determine your longitude

3. Polaris – found in the Little Dipper

4. To find latitude: If you know the altitude of the North Star or Polaris you can find your latitude THE ALTITUDE OF POLARIS IS EQUAL TO THE LATITUDE OF THE OBSERVER!!! Altitude = Latitude

5. Longitude Based on Earth’s rotation The Earth rotates 15°/hour 360° ÷ 15° = 24 hours! People on the same line of longitude have the same local time

6. To find longitude: Must know – your local time and the time at the prime meridian – if you are east or west of prime meridian Determine time difference Multiply difference by 15°

7. How to subtract time: Place the larger time on top of the smaller time. 12:00pm (GMT) -4:00pm(local) 8:00 (difference in hours) Now multiply the difference in hours by 15° If GMT is earlier than local time, your longitude is W. If GMT is later than local time, your longitude is E. W e E l

8. Subtracting time examples: 11:00am (GMT)9:00pm (GMT) -5:00am (local)- 7:00pm (local) 4:00pm (local)6:00pm(local) -3:00pm (GMT)-1:00pm (GMT)