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Colors of a Warrior

This is M42, the Great Nebula in Orion. When you look at Orion in the sky, you can actually see this nebula naked-eye. Located between Orion's feet and belt are three stars that make up his sword. The middle "star" is actually this nebula, which is a star-forming region, or "stellar nursery" -- a place where new stars are being born. See also Orion's True Colors and Warrior Blues.

About the Title:
This nebula, M42, is located in the constellation Orion, and is often referred to as "the Great Nebula in Orion". Orion was a warrior, so these are the colors of a warrior.

How we made this picture:
This image began with sixteen exposures: six with the blue filter and five in each red and green (visible). All images were taken through the 16-inch ASKO telescope in the Orson Pratt Observatory. The length of the exposures varied with color, i.e. 30 seconds in blue, 8 seconds in red, and 12 seconds in green. This way the photon counts were approximately equivalent in each filter. We saved these original images as bitmaps in Pictor, allowing it to auto-adjust the grayscale. Then in Corel Photo Paint, we combined the bitmaps for each color by merging the darkest pixels. We found that this process brought out the best detail in the image. It also eliminated noise and, as the images were all offset from each other, it eliminated defects from faulty pixels on the CCD. We then had three images, one in each color. These were merged in a straight 1:1:1 ratio. The resulting image is this: "Orion's True Colors".
I was, however, unsatisfied with this result. Due to variations in surface brightness, very little of the nebula could be seen. So we went back to Pictor, to the original .FTS images. For each of the original 16 images, we adjusted the grayscale four times. We slid it down thirty-three steps to get the Trapezium, five steps to get the nebulosity surrounding the Trapezium, and we slid it up five steps and ten steps to get the outer edges of the nebula. Thus we had 64 new bitmaps.
We took these images back to Corel Photo Paint, and repeated the process mentioned above (i.e. combining the dark pixels, then merging the three colors). We then had five color-images of different levels of brightness of the nebula. Combining these into a single image was perhaps the most difficult procedure of all. Originally, we had combined the layers (* For ease of communication, I will refer to the different levels of surface brightness as "layers", and the process of merging these layers as "layering". *) before merging the colors together. However, the final three-color image showed rings of colors. This, we realized, was because we were inconsistent in where we defined the edges of the layers in the different colors. Merging the layers after the colors were combined eliminated this problem.
After a bit of experimentation, we determined the best way to layer the image. Starting with the image five steps down from the original, we copied everything except for the very center, where it was overexposed. We then pasted this on top of the image in which the Trapezium was clearly visible. To avoid harsh edges, we then "feathered" the image, which is a process in Corel that gently merges the edge pixels of an object with the background. Therefore we obtained a smooth transition from one layer to the next. We then repeated this for the other three layers.
In the final image, the outer edges of the nebula were somewhat grainy, due to our low counts for that part of the nebula. To eliminate this, we re-combined the original bitmaps in each color, this time in Epoch 2000, so that we could average the values of each pixel. We then merged the colors, and layered the result onto the final image. Thus we produced the beautiful image we call "Colors of a Warrior", visible above.
I would like to extend a special thanks to Liberty Schwendiman, for training me so well on use of the David Derrick Telescope, so that I could produce such work.
For a "blue" version of M42, see "Warrior Blues". (For this one, I increased the blue in our first three-color image, then split it into its red, green, and blue channels. Then I merged the blue channel from that with the original red and green.)
Click here to see the color channels of each layer.

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