Star Trails

This is a first light image with my new Canon 14mm lens, using the modified Canon 50D, captured at the blue/grey LP boundary south of Foymount. The camera was pointed about midway between the pole and the zenith. The mouseover image has some labeled points for reference. The vertical extent is about 76 degrees of arc.

Exposures were 60 seconds at ISO800 and f/5.6, for a total time of about 70 minutes. A slight gap between exposures (it takes time to download to the computer!) is evident toward the top of the image, where the stars move faster. There is one meteor trail present.

The mouseover image is the original, distorted image generated by the lens. I selected this lens because it lacks barrel distortion (straight lines are uncurved) and has relatively low chromatic abberation. However, areas are progressively increased away from the center of the image. As a result, circles are pulled into ellipses. Photoshop contains the necessary data for both the lens and the camera and can correct this distortion with a single menu selection. The corrected image (mouse off, and link) demonstrates this beautifully. The uncropped image has small gaps in the corners as a result of contracting the image there.

March 8, 2013; south of Foymount, Ontario; 14mm lens on modified Canon 50D; 69x60s with no noise reduction; ISO 800 and f/5.6; no filters; temperature was 0 to -5 C; seeing /transparency average.

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