O.K. so not aliens trying to signal us by modifying a star's output (mind you that isn't a bad idea) - but actually a very variable, variable star called WY Cassiopeia near the open cluster NGC7789. This is an animation of two images taken 6 months apart showing the enormous change in brightness magnitude in this star over just 6 months. And yes I did think it was something a lot more exotic than a variable star when I first saw it. Digital image processing as usual by Noel Carboni, image acquisition by Greg Parker at the New Forest Observatory.
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.