Deneb and emission nebulae. Deneb (Alpha Cygni, lower left) is a blue giant, and one of the most powerful stars known. It is the 19th brightest star in the night sky despite its huge distance from Earth. This is estimated to be between 1600 and 3200 light years, exact measurements being difficult at such distances. If the latter is correct, then Deneb is around 250,000 brighter than the Sun. It would be brighter than the full Moon if it was at the same distance as Sirius, the brightest star, which is 8.6 light years away. The bright emission nebulae Sh2-112 (lower right) and Sh2-115 (upper right) are also seen. These objects all lie in the constellation Cygnus. Photographed by the 1.22-metre Oschin Telescope at Mount Palomar, California, USA.