1. Sailing by Starlight: the Lost Art of Celestial Navigation Andrew Thaler

2. Do you know where you are?

3. Finding your way home

4. Finding your way home Southern Sky Northern Sky

5. Finding your way home How do you travel in a straight line? Latitude hook Must be calibrated to a specific location Polaris above the loop, head south Polaris below the loop, head north Kamal Why does this work?

6. Determining Latitude Polaris tan θ = x/y θ = Latitude X θ Horizon y

7. Determining Latitude Accurate to within 1 Degree 1 degree of latitude = 60 minutes 1 minute = 1 nautical mile Polaris is 430 light years away 2.5 X 1015 miles If surveyors were as accurate as Polaris - 0.0000000002 inches If Polaris was as accurate as a surveyors - 4,000,000,000 miles

8. Latitude is θ Cross staff Quadrant Astrolabe Octant Sextant

9. Longitude The X-Prize of the millennium No accurate method until 19th century 3 puzzle pieces Rotation of the earth = 15o per hour Time the sun peaks at prime meridian = 1200 Time (GMT) the sun peaks at your location

10. Relative Longitude Not very accurate! Find a star near the eastern or western horizon Measure the altitude of that star at the same time every night Changes in degrees correspond to movement east or west 2 Caveats Need to correct for latitude Need to know what time it is

11. What time is it? The sky is a clock, too Mariner’s Nocturnal Measures the angle between Polaris and Ursa Major or Ursa Minor

13. Set the dial to the date

14. Sight Polaris through the center hole

16. Questions?