North America Nebula - I'm lost

[waterbourn]

My first attempt at a large nebula, the North America. I struggled stacking it for awhile. It would all be red when i auto developed. I figured out a "use white balance" raw setting in DSS that seemed to correct that. So now I actually see something that makes me think the nebula is actually hidden in there when i autodevelop. But I am out of my depth trying to figure out how to clean it up. I have only dealt in small galaxies before, but this take up most of the screen so I a can't even figure out how to wipe and get a clean picture. I did fight a lot of light pollution. I had to go in my front yard to get to this part of the sky and there is a street light out there. Therefore I only went to 40x 90 sec exposures. I do have darks, bias, and flats added to the stack as well. I was hoping to get some feedback and help on what exactly to do with this one, because everything I try just doesn't look great at all. It may be there is nothing that can be done with it Thanks!

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

[admin]

Oof... That's some tough data...

First off, you really need to dither between frames, as the pattern noise/streaks are pretty severe.

In StarTools, don't worry about the color balance until the last minute (e.g. before switching Tracking off). As a matter of fact, doing any sort of color balancing before you hand your data to StarTools can be detrimental to noise propagation, so don't do it!

Use AutoDev to figure out what's wrong with the image (bias, stacking artifacts, gradients, etc.), correct it, then use AutoDev again (usually with a Region Of Interest - click & drag) for your final stretch.

NANeb.jpg (401.8 KiB) Viewed 5498 times

--- Auto Develop
Default values. We can see severe bias, some gradients, heavy pattern noise, stacking artifacts and (I think) amp glow. Also some oversampling.
--- Bin
Reduce noise and make use of oversampling.
Parameter [Scale] set to [(scale/noise reduction 35.38%)/(798.89%)/(+3.00 bits)]
--- Crop
Getting rid of stacking artifacts and (what I think is) amp glow.
Parameter [X1] set to [79 pixels]
Parameter [Y1] set to [54 pixels]
Parameter [X2] set to [1465 pixels (-59)]
Parameter [Y2] set to [940 pixels (-74)]
--- Wipe
Parameter [Dark Anomaly Filter] set to [5 pixels]
--- Auto Develop
ROI over center of image.
--- Life
Isolate preset.
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Dark Saturation] set to [4.70]
Parameter [Blue Bias Reduce] set to [1.21]
Parameter [Green Bias Reduce] set to [1.15]
Parameter [Red Bias Reduce] set to [1.11]
--- Wavelet De-Noise
Parameter [Scale 1] set to [80 %]
Parameter [Scale 5] set to [50 %]
Parameter [Color Detail Loss] set to [18 %]
Parameter [Brightness Detail Loss] set to [18 %]
Parameter [Grain Size] set to [12.0 pixels]
Parameter [Smoothness] set to [77 %]

And that's it.

[waterbourn]

Thanks!

I always have so many questions. So first about white balance. If I don't check the white balance box in DSS i get this when i a autodev. and if i wipe it then i see nothing behind it. So that is why i had to "white balance" Not really understanding what is happening between the two options, but i get completely different results.

And what exactly is amp glow? Also when you wipe do you use a preset (gradient, vigenetting, etc.) How do you determine which one of those buttons you should choose?

red screen NAN.JPG (271.15 KiB) Viewed 5487 times

DSS white blance.JPG (52.23 KiB) Viewed 5487 times

[admin]

Thanks!
I always have so many questions. So first about white balance. If I don't check the white balance box in DSS i get this when i a autodev. and if i wipe it then i see nothing behind it.

That's fine and expected - it's AutoDev's job to allocate dynamic range to what's most prevalent in your data. In this case it's a nasty red/orange bias. Wipe indeed removes this, however it reapplies the stretch that is currently active. Since the current stretch was created by AutoDev to allocate maximum dynamic range to the red/orange bias, the current stretch is no longer appropriate. You can now go back to AutoDev to let it re-do the stretch and see what other issues it can bring out (or you can use it for your final global stretch). If you read the work flow, I'm doing exactly that. You can also set 'Temporary AutoDev' to yes, which applies a temporary AutoDev to the wiped data so you can better see what your data looks like without the bias/light pollution - it is undone once you exit Wipe. Follow the workflow and you'll see what is happening.

And what exactly is amp glow? Also when you wipe do you use a preset (gradient, vigenetting, etc.) How do you determine which one of those buttons you should choose?

Wipe deals with local (mostly avoidable during acquisition) and global bias (mostly unavoidable) in the signal. You determine which button you should choose by learning what gradients (image as found on http://ontariostargazing.ca/deep-sky-im ... ew-how-to/) , vignetting and amp glow are. Google is your friend!
That said, if you practice 'proper' image acquisition, you should not have to worry about things like amp glow, pattern noise, vignetting and dead pixels. Learning how to fix things in post-processing should be your last resort. Fixing things during acquisition is always better and will yield vastly superior results.