This image was more of an accident than planned. I was experimenting with the focus of the 500mm lens with the K10D. At the time I was fairly disappointed with the in-camera images as they seemed to have bloated stars. This was due to the lens being an achromat rather than an apochromat. However when I got back home I was able to get sharp red channel images from some shots and sharp green and blue channels from other shots. Using Photoshop I was able to combine the best red, green and blue images to give a much improved image.
The Red, Green and Blue channels were made up of separate stacks of 3 fairly short images, typically 10, 25 and 50 seconds. I wish I had taken some longer shots as the end result was much better than expected.