Gum Nebula
Color version selected as Astronomy Picture of the Day on 19 May 2006

Image versions: 1000×591 Hα2500×1477 H&alpha1000×591 HαRGB2500×1477 HαRGB1000×591 HαRGB (annotated)

With a diameter of 36° the Gum nebula (named after the Australian astronomer Colin Gum) is one of the largest Hα emission regions in the sky. It is located in the southern constellations of Puppis and Vela. Relatively little is known about the origin of this object, although it is thought to be the remnant of a supernova explosion one million years ago. The Vela Supernova Remnant appears to be embedded in this nebula, although the two are considered separate objects.

22 narrow-band H&alpha images were combined into a mosaic covering approx. 41°×23°. In addition, a 4-frame color mosaic was assembled from images taken with a Canon EOS 350D digital SLR camera. In the color mosaic, the R channel was "enhanced" with the Hα data ("lighten only" mode); in addition, contrast-stretched copies of the Hα image were superimposed on the G and B channels, resulting in a "semi-false-color" HαRGB image.

Camera Ha: Starlight Xpress SXV-H9, Color: Canon EOS 350D
Lens Ha: Minolta 1.4/50 mm lens, stopped down to f/2.4.
Color: Canon 1.8/50 mm, stopped down to f/4.
Filter Astronomik Ha (13 nm FWHM)
Mount Vixen Super Polaris DX
Guiding manual
Dates Ha: 21/22 Mar. 2004, 24-27 Feb. 2006
Color: 03 Mar. 2006
Exposure Ha: 2x15 min; Color: 6x5 min
Site Ha: Cederberg Observatory;
Color: Koornlandskloof Guest Farm
Processing Bias, dark frame, flat field correction, registration and digital development: IRAF;
mosaic assembly: SExtractor, Match, custom software and Swarp;
post-processing: Gimp

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