M101

[waterbourn]

Still playing around with processing and took a new set of pictures. I feel like some of the stars are so big (bloated). Anything to help minimize that? Any other suggestions based on what the image looks like? I feel like I am having a hard time finding the balance of the second Autodev (after wipe) using the ROI. If I highlight too much ROI I feel like I lose detail in the galaxy but I get a blacker background. If i use a small portion of the ROI I get more detail in the galaxy, but my background retain a redness to it even after decon, life, color, denoise.

[admin]

Apologies - I missed this post before!

I feel like some of the stars are so big (bloated). Anything to help minimize that?

The Magic module is your friend - put the offending stars in a mask and use the Shrink operator. If it's mostly halos that are the problem (e.g. due to poor transparency, you could also try the Tighten operator).

If i use a small portion of the ROI I get more detail in the galaxy, but my background retain a redness to it even after decon, life, color, denoise.

The redness should be fixed by the color module (after a succesful Wipe of course). The image posted looks rather nice at the posted scale, but bears the hallmarks of an image shot with a light pollution filter. Some noise is also visible. Could you maybe share the data set, so we can have a go at seeing where improvements can be made?

[waterbourn]

Not a problem at all. I just appreciate you always answering and helping out.

Here is the stacked file. Always glad to see what can be done with it. This was my second real target since getting all my equipment working. I was in a much darker spot with very little light pollution compared to my normal urban setting. I was not using any filters. I don't think I had the best transparency thought. May have been a small haze of thin clouds that came through at one point.

35 lights at 180 sec
25 flats (using twilight sky)
25 bias
15 dark
25 dark flat

https://drive.google.com/file/d/0B0WZUC ... sp=sharing

[admin]

Thanks for that!

I had a look at the data and the big problem that I can see is that the data has been pre-color balanced, causing noise in the red channel to spike. This in turn greatly increases luminance noise, doing the image no favors.
I had no problem getting rid of the redness however (are you sure you applied the color module as the last step while Tracking was still on?) and was able to achieve a color balance that is extremely similar to all other images of M101 that I've processed (one of the cool things about the Color Constancy algorithm).

See below (Noise reduction not applied on purpose so color can be seen).

M101ST.jpg (241.19 KiB) Viewed 6145 times

Workflow up until that point was something like this;

--- Auto Develop
To see what we got.
We can see oversampled data, light pollution (that has been color balanced! ), some dead pixels.
--- Crop
For better framing
Parameter [X1] set to [848 pixels]
Parameter [Y1] set to [313 pixels]
Parameter [X2] set to [2973 pixels (-1337)]
Parameter [Y2] set to [1952 pixels (-916)]
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Wipe
Used lassoo tool to mask out M101.
Parameter [Dark Anomaly Filter] set to [5 pixels]
--- Auto Develop
ROI over M101.
Parameter [Ignore Fine Detail <] set to [4.8 pixels]
Parameter [Outside ROI Influence] set to [1 %]
The latter two parameters help 1. to ignore the noise grain, 2. reduced the optimisation of the stretch for anything outside the ROI
--- Deconvolution
Auto generated suitable mask (need to click button).
Parameter [Radius] set to [2.4 pixels]
--- HDR
'Tame preset' to reduced core brightness.
--- Life
Isolate preset with full mask set.
--- Color
Things to look for; a yellow core (older stars), blue outer arms (younger stars), speckles of purple/pink (HII knots), good even distribution of all temperatures for all the stars in the field.
Parameter [Cap Green] set to [To Yellow]
Parameter [Dark Saturation] set to [3.60]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [292 %]
Parameter [Blue Bias Reduce] set to [1.02]
Parameter [Green Bias Reduce] set to [1.26]
Parameter [Red Bias Reduce] set to [1.93]

Once again in the final result, we can see that color artifacts were introduced into the core of some brighter stars by the pre-white balancing (and thus clipping of channels). The Color constancy algorithm recovers any color that it can and *will* show color where it detects it.

[waterbourn]

Thanks! So the big question is how do i get data that is not pre-color balanced. I am just using my DSLR Nikon D90 in manual mode. So if their is some other setting I am not aware of that would be awesome to know.

Generally my parameters look similar to you. I did not mask the galaxy in the wipe and I should have. I did not use the HDR step (need to read up on that one). I had blue and green bias reduced, but I probably needed to reduce red more judging by what you did. I kept tacking on until the very end where it does the noise reduction.

So what did your final image look like after noise reduction?

[admin]

Thanks! So the big question is how do i get data that is not pre-color balanced. I am just using my DSLR Nikon D90 in manual mode. So if their is some other setting I am not aware of that would be awesome to know.

The trick is to make DSS ignore the white balance embedded in the RAW files. There may or may not be settings for that in DSS depending on which version you use and if DSS wants to repsect that setting (I've never been able to get it to do that )

See this thread on using dcraw to get non-whitebalanced data if all else fails.