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Friday, June 26, 2009

Solstitial Midnight Panorama at 54° North


Click image to view monster panorama.

I didn't get as far north around the time of the June Solstice this year as I managed last summer, but although I didn't get to see the midnight sun, even at the modest latitude of 54° North it still doesn't really get dark at night—the sky along the northern horizon is distinctly blue, with twilight colours extending toward the East and West. I had hoped to photograph the Northern horizon at local solar midnight on the day of the solstice, but as often happens, the weather didn't cooperate, so here's a picture taken a few days before, on the night of June 17–18, at about 23:00 local solar time (civil time was just past midnight, but as summer time was in effect, the wall clock was an hour ahead of the Sun).

Because both the curve of light and dark and the apparent path of the Sun around midnight are close to flat around the date of the solstice, a few days early and one hour before midnight don't make a lot of difference in how the sky appears, so this is pretty close to how the sky would have appeared were it visible at all at midnight on the 20th or 21st. Low-altitude clouds are visible against the sky, but toward the North high-altitude noctilucent clouds remain in the grazing sunlight in the high mesosphere, 76 to 85 km above the Earth's surface.

The panorama was assembled from 13 photographs taken with a Nikon D300 digital camera and Nikkor 18–200 mm zoom lens at a focal length of 18 mm and aperture of f/3.5. Exposure was 2 seconds at a sensitivity of ISO 200; the lens was scale focused to infinity. The panorama was assembled from the individual frames with Hugin, Panorama Tools, and Enblend, then postprocessed with The GIMP. The assembled panorama is 6230×1720 pixels, for an aspect ratio of 3.6:1. Click the image above to view the full panorama, then use your browser's scroll bars to explore it. Since human vision perceives intensity logarithmically, I have applied a “gamma correction” to better approximate the visual perception with a dark adapted eye. The colour in the image is not an artefact of long exposure time: it was just as apparent to the eye; in fact, more detail was visible in the dark portions of the scene than was captured by the camera. Maybe next time I'll try to combine panorama assembly with high dynamic range imaging.

If you enjoy panoramic images, check out those previously posted of Lignières and the Alps, Hall Island in Franz Josef Land, and the North Pole.

Posted at June 26, 2009 20:38