I used the Sputnik App on my iPad to determine the location of the Flare and then used my Canon 80D on Manual mode for a 20 second exposure with a Tokina 11-16mm focusing to infinity.
Iridium Flares are caused by the Iridium Satellites which circle the globe providing communication to the world. More information can be found at http://www.skyandtelescope.com/observing/celestial-objects-to-watch/observing-iridium-flares/ The 100 satellites in the family that create unique flares because of how the satellites are built, the sun hits the solar panels reflect sunlight towards the ground which can be seen at night. There are numerous resources to track when the flares will be visible over an area. Photo taken at Stub Stewart State Park, in Buxton, Oregon.