Where is this fog coming from?

[khobar95]

From a white zone I think a CLS-CCD filter would help you, although I don't know if there is such a thing for Nikon, most probably there is. Dust haze might be a possibility too for your data.

I'm using StarTools only for a few months so I'm learning too, I watched all the tutorials, I read the forums here and also experimented myself, many times I process the same raw data 5-6 times with different settings too see how they affect my image. Like I saw in your data some dust on the lens or something that is producing a little blob thingy so when I did WIPE I increased the Dark Anomaly Filter to 4 pixels to try and tell WIPE to ignore those.

The blob is indeed dust, but it's on the sensor. I'm extremely careful and yet I seem to get dust more often than I'd like. It's everywhere here, but that's part of living in the desert. I have a can of compressed air and a soft brush that helps. The sensor seems to be magnetic.

I have tried using a narrow band filter. Normally it's for nebulae but I was planning on shooting M42 later so stuck it on for grins. My initial impression was neither here nor there. My cursory processing did not reveal it had helped bring out more detail, though it did prevent skyglow from killing things altogether. Perhaps when I gain more processing experience I'll be pleasantly surprised.

[admin]

Hi,

I had a look at your data as well. It's quite nice (with the exception of some dust donuts - hence my remark at calibration; flat frames should be taking care of this). You may want to dither next time, as there is clear 'stripy' pattern noise visible.

I would also like to caution about using a light pollution filter, unless you really have to; they wreak havoc on your colors (there is a way around this though). Only use an LP filter if it makes the difference between being able to shoot very faint detail or not. LP is fairly trivial to remove, provided your data is well calibrated.

Anyway, without further ado;

--- Auto Develop
To see what we got. We can see some slightly uneven lighting, bias/light pollution, pattern noise. The data is oversampled (typical with DSLR data at moderate seeing conditions at any sort of magnification).
--- Bin
Converting (useless) resolution into noise reduction (better signal).
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
We could probably do with a bit more. Up to you!
--- Crop
To frame M31 cs. better and to remove stacking artifacts.
Parameter [X1] set to [21 pixels]
Parameter [Y1] set to [246 pixels]
Parameter [X2] set to [2421 pixels (-29)]
Parameter [Y2] set to [1510 pixels (-80)]
--- Wipe
Created mask with central part of M31 masked out (as a precaution so Wipe won't mistaken M31 as some sort of gradient), as well as the 2 most conspicuous dust donuts masked out.
Vignetting preset, with [Dark Anomaly Filter] set to [4 pixels] to catch any small dark anomalies if present.
--- Auto Develop
Final global stretch; chose a Region of Interest over M31.
Parameter [Ignore Fine Detail <] set to [2.6 pixels] (so AutoDev optimises less for the noise/fine 'detail')
--- Contrast
Parameter [Dark Anomaly Filter] set to [3 pixels]
Optimising contrast a little.

Normally I try some Decon, but I'm thinking not much can be gained with this much noise. Feel free to try though!

--- Wavelet Sharpen
Made a mask with 'holes' for the stars (Fat Stars preset in the Auto Mask generator, Grow x 4 or x5, Invert)
Parameter [Amount] set to [273 %]
Parameter [Small Detail Bias] set to [94 %]
Bit of extra detail in the dust lanes.
--- Color
Final color calibration. Automatic calibration (the default settings ST comes up with) works better with non-whitebalanced data (this data appears to have been pre-white balanced).
Fortunately we know what to look for; a yellow core (older stars) and blueish outer rim (younger stars). Also pay attention to the foreground stars, which should display a nice even (random) distribution between star temperatures from red all the way to blue.
Parameter [Cap Green] set to [To Yellow]
Parameter [Dark Saturation] set to [3.00]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [221 %]
Parameter [Blue Bias Reduce] set to [1.29]
Parameter [Green Bias Reduce] set to [1.21]
--- Wavelet De-Noise
To taste. I used a development version and the settings I used will not be applicable in the current release version.

This is what I ended up with, but it probably looks a bit better on a smaller scale.

m31_102514_3.jpg (568.48 KiB) Viewed 5478 times

Hope this helps!

[khobar95]

Thanks very much for the notes and the processing.

I decided to go back and stack more of my data - many images shot over several nights. The camera was not always at the same angle so there were significant stacking artifacts that I decided not to remove (as it would have messed up the scale). Anyway, I had fun experimenting in ST, and here is the result. The color is off, I know, and M110 and, in particular, M32 need help, but I am quite pleased with the overall result.

[Cheman]

I would certainly consider that an improvement!!
Che

[khobar95]

Just working the images, trying to get a feel for things. I think this is a bit better, though I think it's a bit overprocessed. Still would like to redo the companions. Would like to get more blue in the outer regions but I guess that will come with experience.