NGC 6960, otherwise known as the Western Veil Nebula or the Witches' Broom, is one arc of an expanding shockwave caused by a supernova exploding around 10,000 years ago in the direction of the constellation of Cygnus. The arcs trace out the boundaries of a sphere around 60 light years in diameter where the force of the explosion cleared out most of the gas and dust in the region. A quick look at the difference in star density in the lower right and upper left parts of the image clearly demonstrates this.
ASA DDM60 Pro, Pentax 125SDP, Canon 5D Mk II. 72 minutes total exposure.