Flashing Light Hells Canyon. 4 witnesses. Airline Captain.I have been an airline pilot for 26 years and Captain for 15 years.Amatuer astronomer for 30 years and meteorologist.In Hells Canyon on Snake River night of July 23, 2016.Clear very dark night. Many satellites. I was giving 3 other witnesses a “Star Tour” when my brother and I saw a white light flash with the brightness of Saturn. This was to our NW and about 45 degrees up. Distance unknown. Not real close.After a few flashes it appeared to our NE and then all 4 of us watched this light flash numerous times while moving rapidly in about a 40 degree spread. Again about 45 degrees up.For 10 minutes while this light moved and flashed I told the group I have never seen anything like this in my 30 years of looking at the night sky.This was not an aircraft, drone, balloon, satellite.It moved rapidly from one position to the next sometimes flashing twice in quick succession.It finally stopped and after another half hour we retired to camp.No drugs or alcohol by myself or my brother. No one drunk.I've seen a few things over the years as I spend a great deal of time at night watching the sky. But this was 10 minutes of observation in a VERY remote part of the country.Thanks for taking this report.