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The Rosette Nebula is a large, circular H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way. The open cluster NGC 2244 is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter. It was imaged here using with the Starlight Xpress H16 CCD camera on the piggy-back mounted Skywatcher refractor and with the f6.7 Astro Physics focal reducer. Guiding was by the M7C camera on the 14" telescope. This arrangement was necessary because of the angular extent of the nebula (1.3 degree). Exposure was 20 minutes via the H-alpha filter, used as the Luminance, and 5 minutes each for the R, G and B. The image was processed in Maxim DL and Photoshop.
I was disappointed at the amount of noise associated with the nebulous part of the image which may have been due to the slight mistiness in the atmosphere masking the nebulosity. However, the Neat Image software plug-in to Photoshop was quite effective in reducing the noise. The slight vignetting in the corners and the coma distortion of the stars at the edge of field may be caused by the focal reducer, possibly not being at the correct spacing. [Jefferis]