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The California Nebula (NGC 1499) is a large emission nebula in Perseus, situated next to the bright 4th magnitude star ξ Persei (the bright star below the nebula in this image). It is huge in size, spanning over 145 x 40 arcminutes in the sky, and was named for its slight resemblance in shape to the US West Coast state. The main emission line of the nebula is Hα, that is hydrogen emitting at the wavelength 656.3 nm, at the red end of the visible light spectrum. Because of its low surface brightness, the California Nebula is primarily a photographic object, although it can be glimpsed visually in a rich-field telescope using a Hβ filter.
NGC 1499 - California Nebula in Hα, which is part of this image.
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