May 26, 2010
On a beautifully clear evening in eastern Kansas, I was trying out a relatively new transparency film (Fujichrome Provia 400F) in an all-sky camera that I built three years earlier. While, at first glance, it looks like any other all-sky image with the summer Milky Way, further consideration will reveal the image is made up of light from no less than six different sources. Click on this photo to see a labeled image. These light sources include:
1. scattered artificial light from various mercury and sodium vapor sources (light pollution) in the Kansas City metropolitan area (about 65 mi or 105 km to the north and northeast);
2. galactic light from our home galaxy the Milky Way -- seen as individual stars and distant star clouds;
5. sources of light from ionized hydrogen in the Milky Way;
6. airglow light from oxygen in Earth's upper atmosphere.
Photo details: 20-30 minute exposure; 16 mm fisheye-NIKKOR at f/5.6; on an old Mamiya 120 film back; film speed pushed 2 stops to ISO 1600. Photographed from Linn County, Kansas, at the time of the autumnal equinox, in 2001.