After coasting for a few minutes in the parking orbit, the Lockheed Martin Atlas 5 rocket's Centaur second stage was re-ignited to propel New Horizons out of Earth orbit. This movie covers the completion of Centaur's second burn, spin up, separation and firing of the solid-fuel ATK Star 48 third stage provided by Boeing, and then deployment of New Horizons to conclude the launch.
Source: NASA TV (5 min 58 sec QuickTime 6 file)
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