StarTools

I took your tutorial with my M51 data and produced this image with the Alpha version of ST. Hard to believe it was hiding in that mess of a first Auto-Dev!

The Life module is amazing and I used the dust bunny trick with the Heal module to simulate me not being too lazy to take flats. On an earlier try I set a a pretty large mask around the M51, the companion galaxy and "finger" before using Life. I thought maybe I was artificially creating nebulosity where none existed so I started over and set a very tight mask around the ROI. I was amazed to see the nebulosity still there. It's really hard to believe such detail was lurking in such a noisy image.

One question...I picked up some distortion in the background around the brighter stars. I didn't notice is until I thought I was done so I don't know where it happened. Life module maybe? I don't know if the attached image is high enough resolution to see it. A higher res copy is at http://www.astrobin.com/full/50004/?mod=none

Thanks for your help Ivo. Now I have to redo the other images I've taken in the last few weeks.

Fantastic work!

gminder wrote: I thought maybe I was artificially creating nebulosity where none existed so I started over and set a very tight mask around the ROI. I was amazed to see the nebulosity still there. It's really hard to believe such detail was lurking in such a noisy image.

The Life module works by detecting super structures (e.g. 'big things') in the areas that you allow it to. It then lets you augment these structures, keeping the detail within it stable. Creating nebulosity that isn't there can indeed be done if you do your best, but you'd have to deliberately feed it misinformation on where the 'big things' are.

One question...I picked up some distortion in the background around the brighter stars. I didn't notice is until I thought I was done so I don't know where it happened. Life module maybe? I don't know if the attached image is high enough resolution to see it. A higher res copy is at http://www.astrobin.com/full/50004/?mod=none

This is a 'feature' of the correlation parameter in the denoise module. Correlation basically tries to - to the best of its abilities - guess whether detail around something that is *definitely not* noise (e.g. a big blob like a star, or a dust lane in a DSO, or a spiral arm in a galaxy), is then maybe also not noise. Often it gets it right and that detail was indeed real detail, so it doesn't attack it as noise. Sometimes it gets it wrong and it was just noise and it just leaves it there.

So, the distortion that you're seeing is just remnant noise (it's not introduced). Now the good news is that ST tries to leave this noise in in such a way that it's psychovisually inconspicuous, looking at the image as a whole. It's comparatively hard to pick up on it, as ST does it in such a way that the psychovisual attention is usually with the structure that's directly adjacent (e.g the star), because that offers a much bigger contrast difference and commands much more attention.

It's a little bit like you don't notice JPEG artifacts until you start looking for them. Ofcourse, you can tweak the denoise module to get rid of this altogether.

Thanks for your help Ivo. Now I have to redo the other images I've taken in the last few weeks.

Awesome - keep us posted!