Iridium Flare and Arcturus

Iridium is a constellation of more than 70 communications satellites that are continuously circling the Earth. Iridium flares occur when sunlight reflects off an antenna of one of the satellites; they last only a few seconds and look like a slow-moving meteor. These flares can be as bright as magnitude -8, and can easily be seen even from the city, but when seen in truly dark skies they are a brilliant sight against the background stars! I photographed this magnitude -8 flare in a remote part of the Arizona desert. I left the shutter open for 10 minutes and let the stars drift through the frame; the brightest star at lower left is Arcturus in the constellation of Bootes.

Iridium flares are much easier to view and photograph than meteors, because they can be accurately predicted! The Heavens Above web site can tell you what flares will be visible from your location. You can pick from a list of major cities, but since Iridium flares are very location-sensitive, enter your exact location in latitude and longitude (preferably within 0.01 degree of latitude and longitude, or about 1 kilometer). The site will tell you exactly when and where to look for each flare, as well as how bright it will appear. One hint: the orbits do change over time, so be sure to download a fresh prediction within a day or two of when you plan to observe. Good luck and good viewing!

Location: Sentinel, Arizona
Date: April 29, 2000
Time: 8:41 to 8:51 p.m. MST
Camera: Olympus OM-1 35mm SLR on fixed tripod
Film: Fuji Provia 100F slide
Focal length: 50 mm
Aperture: f/2
Exposure time: 10 minutes
Scanner: Nikon Coolscan LS-2000 (cropped)