A few processing questions (noise & color)

[Chunkles]

Hi,

I have been playing with StarTools for a few weeks now and really like it. But when I see and read of some other's workflows. I'm not getting quite the same results. My issue could very well be my images. I have not received my SkyTracker yet, so am taking shots with my DSLR from a red zone on a tripod. This example image (shared below) is M42. Taken using a unmodified T3/1100D, 200mm f/3.5, 40 subs of 2 seconds, 15 darks, 10 bias stacked in DSS with (I think) no processing. (ISO 3200 in this case just trying to get the histogram over to around 30% with only 2sec exposures at f/3.5)

I can see from the autodev that there is definitely some data there. I then crop and bin. Try to mask out the nebula and wipe. Then autodev again. Sometimes I use contrast and/or HDR. It's when I get to the color module that I seem to mess everything up. Then when I turn tracking off, the de-noising still doesn't help me much. I can use Isolate to grab the nebula, but then the rest of the image looks artificially black.

In my sample tiff file shared here, I had screwed up the stars when trying to create a mask that didn't also think every little bump was a star also. And of course, the colors are crazy by the time I got through with it!

Anyway, if anyone can take a look (sorry about the gigantic size of the FTS file). I'd love to see what someone else can do with their processing steps included. Maybe I'm just doomed until I can start tracking and get longer exposures than 2 seconds!

Thanks so much!

https://www.dropbox.com/sh/qd83qyaru49k ... lsSka?dl=0

[admin]

Hi,

Having a look now...

[admin]

Ok, I had a look at your data and honestly, you've done a pretty good job with what's there! There is simply very little signal to work with, so if you push it, noise will take over. Longer exposures are very much needed...
It doesn't sound like you're doing anything terribly strange with the workflow you outlined, but I am a bit surprised with the colors, which should definitely be recoverable despite the low signal. Are you sure you apply the color module as one of the last steps before switching Tracking off (and availing of noise reduction)? There *is*, however, some wicked chromatic aberration going on, which colors some of the stars a a deep saturated blue.

The image below demonstrates the 'roughly' balanced colors for M42, which shows a cyan/greenish trapzium (rich in OIII emissions) and a mixture of cyan and pink showing the various mixtures of Ha and Hb emissions. The running man is also faintly blue in this data. The stars in the field show a reasonable mixture of temperatures from deep red to blue (not withstanding the skew due to blue haloed stars due to the chromatic aberration).

m42.jpg (45.39 KiB) Viewed 5297 times

I can show you various tricks to keep the noise under control, but at the end of the day these become less and less important once you've passed the (roughly) 2 min mark for your sub-frame exposures.
For example, I used the Life module's Isolate preset to push back some noise; it keeps the larger scale structures but pushes back fine noise and small specks (such as stars).

[Chunkles]

Thanks Ivo! I had a feeling it was due to my less-than-stellar signal (pun intended).
I can't wait for my SkyTracker so I can start getting some decent exposure times! As to the halos, I'm going to do some experiments with my different lenses and at different f-stops to narrow down that issue.

Really appreciate the assistance you provide to all of us and I'm sure I'll have some more questions later.

Thanks!
Scott