Morning Twilight

Last Wednesday morning after a productive night of observing, the twilight grows bright as sunrise approaches. Some distant clouds are lit orange and the Earth's shadow sinks in the last moments of twilight. The Spacewatch 36 inch dome is still open (that was my next stop before heading to bed) and the Steward Observatory 90 inch Bok telescope dome and Kitt Peak 4-meter Mayall telescopes are at right. This image was taken with my 24mm lens at f/2.8 with an exposure of 1/250 seconds, ISO 400.