July 27 2005 - Processing of M27

This is how I process a typical image and the improvements that are made if you stack a raw image.
1. Starting from the left picture. This is a single raw 15 second frame. As you can see it has alot of noise, it apears very grainy and the nebula is barely visible. But the good thing is that this single image as well as the other single raw images have enough data that by stacking and processing we can bring out what we want to see and try and leave behind the undesired noise. Normaly the more raw frames you take the better it is.
2. The second frame from the left is the result of when you stack the images together. If you look closely much of the noise and the grainyness has been elliminated. Ofcourse there is still alot of noise and the nebula still appears rather dim. The next step is to try and bring out the nebula. This can be done several different ways like stretching. I did this one another way I just multiplied the image by itself to get a much brighter image wich shows some more detail in the nebula. Unfortunatly when you do this, the noise also gets brighter and the effects of vignating get very bad.
3. The third image from the left is the resulting picture when you make it brighter.
4. Thee final step is to try make the background dark while keping the nebula and stars bright. This is VERY hard to do esp on this image since it suffers from vignating (the uneven background). What tends to happen is that if you want to entirly get rid of this ugly bacground, you loose almost all the detail of the nebula. I tried a new way of doing it and that was by taking the original brightened image darkening the background just enough but not enought to get rid of the detail then i would save that image. after saving the image i took the average of that new image and the original to form a third image. In the third image I again darkened the background and repeated the steps until finaly I isolated the nebula to the best of my ability. this step took about 10 steps to get to the final image. Ofcourse I did loose some of the faint nebula detail but the darker background makes for a more appealing picture.