Three examples of the combination of red, green, and blue filtered grayscale images into one of color using the technique I described previously.
NGC 2440
When a star similar to our sun reaches the end of its life, it blows off the material near the surface in a colorful “last hurrah” nebula. The grayscale images I used for this picture were taken on Feb. 6, 2007, by the Hubble Space Telescope. See their color image. The outer layers of gas had formed a cocoon around the star core. Ultraviolet light from the star now makes the debris glow. Different colors indicate elements of hydrogen, helium, oxygen, nitrogen, etc. The white dot burned-out star in the center is called a white dwarf. Our sun will do the same in about 5 billion years. Follow this link to a short video describing the location in Puppis southeast of Sirius and Orion. Click images to embiggen.
From original grayscales |…
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Our View From Iowa 