I decided to try a different method tonight. It looks pretty much the same, but is a bit more crisp.
I followed a tip that JohnH posted yesterday; the advice was that of Jerry Lodriguez on the Astropix site. Instead of Screen'ing all my individual layers together, I added them as Normal but at 50% opacity. This has the effect of averaging I believe. And, the more images you stack this way, the less noise.
Once all images were added as Normal @ 50% opacity, I flattened the image. I ended up with five images for each of the five ISO's my camera shoots at. I then added those five images together via Screen. Again, I've used gradiented layer masks to bring out detail in the Trapezium. This time, you'll notice the four stars are visible (I can actually see five when I'm zoomed in at 1600x in Photoshop when registering the large resolution images), and the dark cloud in front of the Trapezium has a lot more structure and form to it than last time.
Thank you to everyone for your kind words of encouragement. I really appreciate them -- I wouldn't be up at 5 AM, otherwise!
Instead of Screen'ing all my individual layers together, I added them as Normal but at 50% opacity. This has the effect of averaging I believe. And, the more images you stack this way, the less noise.
You are correct here, combining two images at 50%, produces an average. Be aware that when you add the 3rd image, the opacity must be at 33% to maintain a true average. The 4th image is blended at 25%, the 5th at 20% and so on. If you use 50% each time, you will end up with an image that is made up of half of one noisey frame.
Excellent work! Using layer masks already is a great step forward to reduce the burnt out core that you see in so many M42 shots. Nice work.
Hey Mike!
Yeah, I've been using Photoshop since version 4 was released in 1996 or 1997. I used to dabble in 3D graphics so got used to using Photoshop to create texture maps as well as as bump maps. Masks are mans best friend!
You are correct here, combining two images at 50%, produces an average. Be aware that when you add the 3rd image, the opacity must be at 33% to maintain a true average. The 4th image is blended at 25%, the 5th at 20% and so on. If you use 50% each time, you will end up with an image that is made up of half of one noisey frame.
cheers
Hi Tony,
I didn't think about the inverse relationship. Thanks for that. I can easily fix that as the files are saved as PSD's. I'll give that a go later on today and update this current thread with a new image side by side with the earlier one.
Greatly appreciate your advice. Your images are remarkable -- your web page has been bookmarked.
It's a big improvment on the original.
It will be interesting to see how you go when you stack using the inverse relationship. Should improve it even more.
