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Circumpolar Star Trails

Circumpolar stars appear to rotate around the north celestial pole due to the Earth's rotation.

The Sun, Moon, planets and stars seem to rise in the east and set in the west in the northern hemisphere. This apparent motion is not because these objects actually move across our sky, but because the Earth rotates on its own axis like a spinning top as it revolves around the Sun.

This image is a composite made of 58 individual frames taken on a fixed tripod pointed north. Each exposure was 6 minutes long for a total of 348 minutes (5.8 hours) of rotation.

Over time, the exposures trace out the paths of individual stars.

Exposure Data
  • Lens: Canon 18 - 55mm f/3.5 to f/5.6 EF-S IS Zoom lens
  • Focal Length: 18mm
  • Focal Ratio: f/5
  • Exposure: 58 x 360 seconds = 348 minutes total exposure
  • Mount: Fixed tripod
  • Guiding: Unguided
  • Camera: Canon EOS 20Da DSLR
  • Mode: JPEG
  • ISO: 400
  • White Balance: Custom
  • In-Camera Noise Reduction: Off
  • Filter: None
  • Date: September 14, 2010
  • Start Time: 10:04 p.m. EDT
  • Location: Maxwell, NJ
  • Calibration: None
  • Processing: Composited in StarTrails, adjusted and enhanced in Photoshop CS5



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