California Nebula
The California Nebula (NGC 1499/Sh2-220) is an emission nebula located in the constellation Perseus. Its name comes from its resemblance to the outline of the US State of California in long exposure photographs. It is almost 2.5° long on the sky and, because of its very low surface brightness, it is extremely difficult to observe visually. It can be observed with a H"α" filter (isolates the H"α" line at 656 nm) or H"β" filter (isolates the H"β" line at 486 nm) in a rich-field telescope under dark skies. It lies at a distance of  about 1,000 light years from Earth. Its fluorescence is due to excitation of the H"β" line in the nebula by the nearby prodigiously energetic O7 star, Xi Persei . The California Nebula was discovered by E. E. Barnard in 1884. By coincidence, the California Nebula transits in the zenith in central California as the latitude matches the declination of the object.