This animation is of two images of the open cluster NGC7789 taken over a year apart, and was created by Noel Carboni, Florida, U.S.A.
Just below the cluster there is a star whose brightness has changed from a very dim magnitude 14-15 to something around magnitude 7 over the space of a year! Although at first sight this looks like a classic example of an alien attempt at bringing their existence to our attention - it is actually the variable star WY Cas in Cassiopeia. I had no idea variable stars could undergo such huge changes in magnitude - thank you Roger Pickard of the BAA for educating me about these fascinating objects.
Nexstar 11 GPS, 2 x Sky 90, M25C, MaximDL, Photshop CS3, Noel Carboni's Photoshop actions, 7 foot Pulsar fibreglass dome, Canon 40D, 100mm macro lens, 28-200mm zoom lens, 17-55mm f#2.8 zoom lens, 100-400mm zoom lens, 1.4x converter, 2x converter.