M 81 and M 82

[Stefan B]

Hi Dietmar,

I had a go at your very nice data set and this is what I came up with:

Dietmar M81.jpg (236.51 KiB) Viewed 9145 times

There's not much difference to your version. It's a lot of signal considering it's only one hour of integrated exposure time. The most striking difference is probably that the core of M 81 looks a bit burned in your rendition. Maybe you have used FilmDev and overstretched a little?

The stars are a bit oblong. The mount is probably at its limits as you already wrote The data had a very homogeneous gradient which was very easy to get rid of in Wipe. That's nice ... recently I had problems with several gradients in my images which had different directions. A real pain.

I guess you stacked in DSS? At least it looks like my stacks in DSS. I recommend to just try one of the other free stackers like ASTAP or Siril. I know that this means getting to know another software and stuff but in my experience it's really worth it. In my hands other stackers always resulted in better stacks with less grainy noise and a better SNR in general. I think there's more in the data than your stack shows

I binned to 50%. In my eyes the image and especially the stars got blocky with 40% or below.

In Wipe I used a high 'Dark Anomaly FIlter' value of 11 pixels. This may seem high, but I am used to this from my own data. This optimizes the wipe of the color data. It's striking to have a look at the color data with a value of 1 and afterwards around 10. Most background pixels are red with a value of 1 pixel and you get a homogeneous background with a value of 10. Makes the work in the Color module much easier.

Otherwise I used mostly defaults. In Color I used a high dark saturation to get some color in the fainter arms of M 81. In SuperStructure I used 'DimSmall' with 75% strength and afterwards the 'Saturate' preset with about 150% saturation. After noise reduction I went to FilmDev module and entered a SkyGlow value of 2% in order to push the histogram a bit to the right.

As already said not that much different to your rendition. Hope this helps a bit nonetheless.

Best regards
Stefan

[Stefan B]

Hi Dietmar,

I wrote before reading your post

- bright sky

Wouldn't have guessed this. Pretty good SNR for only 1 hr.

- probably problems with collimation

I am not experienced enough to even notice this

- Do you observe obvious mistakes in my processing with StarTools?

As already said, I think you burned the galaxy core and some of the stars? A FilmDev issue? I used more star shrinkage for sure but that's optional of course. In my eyes that's important for the impact of the DSOs.

- I often have problems to archive an acceptable background. Either it is to dark and only black or it looks kind of blotchy – I believe, due to flattened noise.

Same here. I use the SkyGlow parameter in FilmDev at the very last step if my background has gotten to dark. If it is too bright you might want to try the 'Isolate' preset in 'SuperStructure' with different strengths. Or you could try to redo a global stretch right before noise reduction if you have the impression you stretched too much or not enough.

- What do you think – would more integration time lead to noticeable improvement of quality? I’m always insecure, if this would make sense under such a bright sky.

Definitely! Just try a whole night with four hours or more and I am sure you will be blown away by the difference.

Regards
Stefan

[decay]

Hi Stefan,

first of all: thank you very much spending your time processing this data set and for your remarks!

I really like your result and there are some obvious pros compared with my result (e.g. stars, background, colour) . I will try to analyse this one by one with respect to your remarks and if it would be right for you I will report back separately to each topic. (Of course, without need to answer from your side.)

Best regards, Dietmar.

[decay]

Hi Stefan,

could you please post the log of this Startools session?
Thanks!

Best regards, Dietmar.

[Stefan B]

Hi Dietmar,

there you go:

Code: Select all

File loaded [C:\Users\stefa\Pictures\Astro Bilder\ST forum\Dietmar M81 M82\Dietmar M81.fts].
Image size is 5998 x 3983
--- 
Type of Data: Linear and was Bayered, but not whitebalanced
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [5998 pixels (-0)]
Parameter [RoI Y2] set to [3983 pixels (-0)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Bin
Parameter [Scale] set to [scale 50.00% / +2.00 bits / +1.00x SNR improvement]
Image size is 2999 x 1991
--- Crop
Parameter [X1] set to [268 pixels]
Parameter [Y1] set to [506 pixels]
Parameter [X2] set to [2691 pixels (-308)]
Parameter [Y2] set to [1639 pixels (-352)]
Image size is 2423 x 1133
--- Wipe
Parameter [Synthetic Dark/Bias] set to [Off]
Parameter [Gradient Edge Behavior] set to [Absorb 50%]
Parameter [Synthetic Flats] set to [Off]
Parameter [Sampling Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [11 pixels]
Parameter [Gradient Falloff] set to [0 %]
Parameter [Synth. Bias Edge Area] set to [100 %]
Parameter [Gradient Aggressiveness] set to [81 %]
Parameter [Correlation Filtering] set to [Off]
Redoing stretch of linear data
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [5.2 pixels]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [1605 pixels]
Parameter [RoI Y1] set to [557 pixels]
Parameter [RoI X2] set to [2162 pixels (-261)]
Parameter [RoI Y2] set to [635 pixels (-498)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Brightness Retention] set to [Off]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Shadow Detail Size] set to [10 pixels]
Parameter [Locality] set to [50 %]
Parameter [Shadow Dyn Range Alloc] set to [50 %]
--- HDR
Parameter [Signal Flow] set to [Tracked]
Parameter [Quality] set to [Low]
Parameter [Gamma Shadow (Lift)] set to [1.00]
Parameter [Gamma Highlight (Tame)] set to [1.25]
Parameter [Gamma Smoothen] set to [20.0 pixels]
Parameter [Context Size] set to [50x50 pixels (2.06% image W, 4.41% image H)]
Parameter [Shadows Detail Boost] set to [30 %]
Parameter [Highlights Detail Boost] set to [30 %]
--- Wavelet Sharpen
Parameter [Structure Size] set to [Large]
Mask used (BASE64 PNG encoded)


--- SNR-aware Wavelet Sharpening
Parameter [Protection] set to [Shadow/Highlights]
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [4 pixels]
Parameter [Amount] set to [300 %]
Parameter [High SNR Size Bias] set to [85 %]
Parameter [Low SNR Size Bias] set to [0 %]
Parameter [Dark/Light Enhance] set to [50% / 50%]
Mask used (BASE64 PNG encoded)

PSF samples used (15 PSF sample locations, BASE64 encoded)


--- Spatially Variant PSF Deconvolution
Parameter [PSF Resampling] set to [None]
Parameter [Synthetic PSF Model] set to [Circle of Confusion (Optics Only)]
Parameter [Sampled PSF Area] set to [15x15]
Parameter [Synthetic PSF Radius] set to [1.5 pixels]
Parameter [Synthetic Iterations] set to [Off]
Parameter [Spatial Error] set to [1.00]
Parameter [Deringing Fuzz] set to [20.0 pixels]
Parameter [Deringing Detect] set to [50 %]
Parameter [Dyn. Range Extension] set to [1.00]
Parameter [Linearity Cutoff] set to [85 %]
Parameter [Sampled Iterations] set to [10x]
Parameter [Deringing Amount] set to [0.80]
--- Color
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Matrix] set to [Identity (OFF)]
Parameter [Dark Saturation] set to [6.7]
Parameter [Bright Saturation] set to [5.4]
Parameter [Saturation Amount] set to [200 %]
Parameter [Blue Bias Reduce] set to [1.04]
Parameter [Green Bias Reduce] set to [1.09]
Parameter [Red Bias Reduce] set to [1.23]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Cap Green] set to [100 %]
Parameter [Highlight Repair] set to [10 pixels]
Mask used (BASE64 PNG encoded)

--- Shrink
Parameter [Mode] set to [Dim]
Parameter [Halo Extend] set to [2 pixels]
Parameter [Iterations] set to [7]
Parameter [Regularization] set to [0.85]
Parameter [Color Taming] set to [0 pixels]
Parameter [De-ringing] set to [Off]
Parameter [Un-glow Strength] set to [Off]
Parameter [Un-glow Kernel] set to [Off]
--- Super Structure
Parameter [Detail Preservation] set to [Linear Brightness Mask Darken]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Brightness, Color] set to [Process Both]
Parameter [Brightness Retention] set to [Local Median]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Airy Disk Radius] set to [50 %]
Parameter [Gamma] set to [0.75]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [50 %]
Parameter [Strength] set to [74 %]
--- Super Structure
Parameter [Detail Preservation] set to [Linear Brightness Mask]
Parameter [Compositing Algorithm] set to [Screen]
Parameter [Brightness, Color] set to [Only Color]
Parameter [Brightness Retention] set to [Off]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Airy Disk Radius] set to [50 %]
Parameter [Gamma] set to [0.50]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [168 %]
Parameter [Strength] set to [100 %]
--- Unified De-Noise
Parameter [Grain Size] set to [12.0 pixels]
Parameter [Walking Noise Size] set to [1.0 pixels]
Parameter [Walking Noise Angle] set to [0]
--- Unified De-Noise
Parameter [Scale 1] set to [99 %]
Parameter [Scale 2] set to [95 %]
Parameter [Scale 3] set to [95 %]
Parameter [Scale 4] set to [95 %]
Parameter [Scale 5] set to [50 %]
Parameter [Equalized Grain] set to [24 %]
Parameter [Scale Correlation] set to [50 %]
Parameter [Color Detail Loss] set to [50 %]
Parameter [Brightness Detail Loss] set to [50 %]
Parameter [Grain Dispersion] set to [12.0 pixels]
--- Photographic Film Development Emulation
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [2 %]
Parameter [Digital Development] set to [Off]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [12.0 pixels]
File saved [C:\Users\stefa\Pictures\Astro Bilder\ST forum\Dietmar M81 M82\Dietmar M81.tiff].
Loading red channel data

I deleted the masks but left the indication where one was used. I mostly used default star masks, but cleared the accidentally masked core structures of both galaxies.

Have fun and let me know how it goes!

Regards
Stefan

[decay]

Hi Stefan,

thank you very much for posting the log.

Meanwhile I analysed my own log and I found the reason for the burned galaxy core.

As already said, I think you burned the galaxy core and some of the stars? A FilmDev issue?

Usually I do use AutoDev, as recommended. But I admit, I often still have problems finding a resonable ROI. In this case I was focused on the nice structures of M82 and so the core of M81 was ... disregarded in some way Probably not one of my better ideas

QuiteSillyROI.jpg (53.29 KiB) Viewed 8910 times

To be continued ...

Best regards, Dietmar.

[admin]

Hi Dietmar (and thanks Stefan! )

The AutoDev documentation explicitly mentions what to do in the case of the M81/M82 pair (and why it behaves the way it behaves).

Have a look at the documentation in general, to get an idea on how AutoDev and the ROI works, so its workings will be less of a mystery.

I hope this helps!

Ivo

[Stefan B]

What Ivo said (or referenced ). With time one gets used to immediately look for a part of the image which is a good example of the dynamic range you want to show (or hide, respectively). Galaxies are easy in that regard, since they have a bright core and get fainter towards the periphery. Just take a slice of the galaxy, include the core and try including or excluding parts of the fainter arms. Nebulae (or star clusters) are a bit more tricky. Here it would be nice if one could choose more than one ROI and wouldn't be limited to a rectangular ROI

Regards
Stefan

[decay]

Hi Ivo,

thank you for pointing out to the documentation with the M81/M82 example. That's a bit embarrassing; I swear, I read the documentation, but it may be some time ago. It must have been some kind of blackout, I was so concentrated on M82 that I didn't realized the impact on M81.

In principle I understand how the AutoDev module behaves and most times I get a reasonable result. And as Stefan stated, over time it's getting more easy and faster to find a suitable ROI.

Best regards, Dietmar.

[decay]

Hi Stefan,

last days, I took a view on your logfile and found found some interesting and really helpful insights to your development process. I will write down some notes in posts later on.

At the moment, I have a question concerning the use of the SVDecon module: Referring to the log you used the default settings, except for [Synthetic PSF Model] was set to [Circle of Confusion (Optics Only)]. These settings have no visible impact to the image at all, but I am quite sure, that deconvolution took place – your rendition is much “sharper” than the result obtained with this (default) settings.

Do you remember, what settings you chose or adjusted for SVDecon? (A hint would be enough, please don’t do it all again! And, once again – this is not urgent.)

Have restful Easter holidays.

Thanks & best regards, Dietmar.