I took a 50-minute RGB image (50:50:80 minutes in RGB) of the Cocoon just the other night at New Mexico Skies. I have been trying to get a good color picture that would reveal the structure of the various layers of nebulosity that are present in this area. By chance, one of my fellow imagers walked in a moment ago and helped me understand what is going on in this image.
First, he suggests that this is a "Stromgren" sphere (spelling uncertain). That is a sphere of Hydrogen gas that is ionized by a central star, emitting deep red (H-alpha). Outside the sphere, the radiation from the star isn't bright enough to ionize the Hydrogen, so it glows with light reflected from the star. In this image, you can see the deep red of the ionized hydrogen, and a faint white glow around this (with a slight blue cast) that is reflected light.
Second, the dust lane that extends outward from the Cocoon is dark but also bright enough to be imaged. The dust is a deep rust-red color. An analysis of the individual R, G, and B images shows that there is a thick cloud of dust at lower right (perhaps a Bok Globule?), a lane of dust that is thinner and shows some stars through it, and a light haze of red dust generally over the lower half of the image.
My goal is always to use color to reveal structure in an image, and this example is one that really does that well. This a roughly half-size version of the image. I am on the road, and I cannot post a full-size version to my web site until I return home.
Ron Wodaski
author of "The New CCD Astronomy"
http://www.newastro.com
First, he suggests that this is a "Stromgren" sphere (spelling uncertain). That is a sphere of Hydrogen gas that is ionized by a central star, emitting deep red (H-alpha). Outside the sphere, the radiation from the star isn't bright enough to ionize the Hydrogen, so it glows with light reflected from the star. In this image, you can see the deep red of the ionized hydrogen, and a faint white glow around this (with a slight blue cast) that is reflected light.
Second, the dust lane that extends outward from the Cocoon is dark but also bright enough to be imaged. The dust is a deep rust-red color. An analysis of the individual R, G, and B images shows that there is a thick cloud of dust at lower right (perhaps a Bok Globule?), a lane of dust that is thinner and shows some stars through it, and a light haze of red dust generally over the lower half of the image.
My goal is always to use color to reveal structure in an image, and this example is one that really does that well. This a roughly half-size version of the image. I am on the road, and I cannot post a full-size version to my web site until I return home.
Ron Wodaski
author of "The New CCD Astronomy"
http://www.newastro.com
Attached Image:
Ron Wodaski
New Astronomy Press
http://www.newastro.com
