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The Sh2-155 (Sharpless 155), or Cave Nebula, is a faint but large region of double ionized hidrogen, surrounded by dust, that lie in the constellation Cepheus. The area is rich in detail and very colourful, due to the red emission from ionized hidrogen and the blue of reflection nebulae. The area is populated by many dark nebulae, some very prominent and detailed. One of these is the the central "cave-like" structure.
In order to produce the color image
seen here, I worked with data coming from 2
different photographic plates taken at Palomar Observatory between 1989
and 1991. The original file is 6,220
× 6,632
pixels with a resolution of about 1 arcsec per pixel. The image show an
area of sky large
1.7°
× 1.8° (for
comparison, the full-Moon is about 0.5° in diameter). Other images of the same celestial field found online
This image is a composite from black and white images taken with the Palomar Observatory's 48-inch (1.2-meter) Samuel Oschin Telescope as a part of the second National Geographic Palomar Observatory Sky Survey (POSS II). The images were recorded on two type of glass photographic plates - one sensitive to red light and the other to blue light and later they were digitized. Credit: Caltech, Palomar Observatory, Digitized Sky Survey. |
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