M81 & M82: Bode's Galaxy and Cigar Galaxy

[decay]

Hi all,

my last try on this galaxy-pair was some years ago and from my beginning with AP and with using StarTools, too. So I decided to dedicate some nights to this object again:

There's one night of NB (duoband) filter data (Ha) in it. Probably not enough, but at least the NBA module brought out some red dots in M81 and these nice red filaments in the cigar.

I followed the Stefan's approach again and visited the NBA module right after the Colour-Module. Running SV-Decon afterwards gave great detail for the red filaments, but of course tightened the red dots in M81 even more. So this is a trade-off.

No Shrink because I don't like into singularities collapsing stars when SV-Decon already did such a great job in tightening the stars. Of course, a matter of taste.

The most challenging part was to bring out at least a bit of the dust clouds including the Arp's Loop. So much noise! Super Structure with reduced strength (60%) and then Noise Reduction at 30px - all in This time I did a small tweak afterwards using GIMP to adjust the shadows in order to mitigate visible background mottling.

(One hint: I usually use DSS to align broadband and NB data sets. This time DSS introduced a strong correlated noise pattern, probably because of the angle difference between the two data sets. Aligning with ASTAP worked very well.)

AB link: https://app.astrobin.com/i/5n1627

Comments most welcome

Best regards, Dietmar.

[Startrek]

Hi Dietmar,
Wow this is an excellent image from your DSLR , so many faint fuzzies in the background with image perfectly framed.
You’ve managed to pick up some Ha detail which is difficult and the background noise has been managed quite well. Startools always has your back.
Some of the whiter stars have a “slight hint” of the dreaded rainbow artefact which can be minimised using Highlight Repair in the Colour module ( up as high as 9 or 10 ) or Shrink set to zero and use colour taming.
I gave DSS away a few years ago, it just doesn’t cut it for my Mono data sets , ASTAP is tremendous, support is excellent ( Han ) and results speak for themselves.
I’ve used the Ha Accent feature in v1.8 a few times now with Ha LRGB data sets and I must say it works beautifully, kudos to Ivo !!!
Well done Dietmar !!

Clear Skies
Martin

[Stefan B]

Very good image, Dietmar! I like the faint stuff which looks very natural and not forced at all. Noise looks well handled. How did you define the ROI during the final stretch? Just a slice of M82 or no ROI at all maybe?

Did you use the same NBAccent parameters for both M 81 and M 82? Several years passed since my last try but I think I used the galaxy preset for M 82 and the nebula preset for M 81 back then.

Almost 25 hrs and six nights? Shows quite some dedication... did you set up the scope for each night again? If so, kudos! If not, kudos anyway

Great work!

Regards
Stefan

[decay]

Thanks for your kind comments, Martin.

Some of the whiter stars have a “slight hint” of the dreaded rainbow artefact which can be minimised using Highlight Repair in the Colour module ( up as high as 9 or 10 ) or Shrink set to zero and use colour taming.

Now that you mention it, I also see it. Mike (in Rancho) would say "some Pepsi action is going on there" Thanks for your advice, I will give that a try.

To be honest, I don't know why I used DSS for aligning while ASTAP for 'normal' stacking (since a long time). Yes, I like ASTAP a lot, but I'm also thankful that there are other stackers available for us, too. Mono-cultures are always a bad thing - as we can see when we look at PixInsight, OSes for PCs, or browsers to explore the internet. But I'm afraid, this is a bit off topic here, sorry

Best regards, Dietmar.

[decay]

Hi Stefan,

thank you!

How did you define the ROI during the final stretch? Just a slice of M82 or no ROI at all maybe?

The ROI comprised M81 as a whole, including the bright stars to the 'left' ( I'm always teaching my children that this is not the way to put it) and some background. No way without ROI, there's far too much noise, surprisingly for me, too. I also thought, that so many hours of integration time should allow to get away without ROI. Maybe it's because of the signal present in this case, compared to other 'backgrounds'. But I should mention, that I pushed Gamma to about 1.3 to get the galaxies bright enough. Which of course amplifies the noise, too.

Did you use the same NBAccent parameters for both M 81 and M 82? Several years passed since my last try but I think I used the galaxy preset for M 82 and the nebula preset for M 81 back then.

Oh, I was not aware, that this is possible?! How do you do that? It was the galaxy preset with reduced Detail Size (50px) and Brightness Correlation (50%), increased Strength (150%) and reduced Gamma (0.9).

did you set up the scope for each night again?

No. Currently is pretty dry here (too dry ) and so I dared to leave the rig outside. I just covered it with the caps and a sheet in the morning.

Shows quite some dedication

Yeah. I think I'm getting near to what is possible using this rig, at this location ... and for me

Thanks again, Dietmar.

[Startrek]

Hi Dietmar,
Below are some ways to use Startools and correct issues with Star colour like Rainbow effect, bicolour halo , excessive saturated colours , narrowband colour artefacts etc…

Star Colour Correction using Filter

The Filter module can help colour correct star halos.
Obviously Filter is used after Colour Module
Filter mode use Fringe Killer
Sampling Method use 3x3
Filter Width try 1 to 5
Mask Fuzz 1.0 pixel to 4.0 pixels
Create a good Star Mask ( including touching up diffraction spikes if using a Newtonian)
Select mode as Fringe Killer
Sampling use 3x3
Click on Star Halo to change colour closer to Star core. Each click will slowly change colour as required.
Adjust parameters as required to achieve best outcome
Press Save once completed


Star Colour Correction using Shrink Module

Create a good Star Mask and ensure all star cores and halos that require colour correction ( including diffraction spikes ) are sampled or green. Grow mask as required

Open Shrink
Adjust iterations to 0
Change Mode to Tighten
Color Taming increase to between 4 and 10 pixels as required.
Note: Be careful not to increase Color Taming too much as this can cause Star cores to bleach out colour or “white out”. Start off with 2 pixels , then 4 pixels and so on until Star colour is reasonably uniform in the core and halo area.
Halo Extend increase to 1 or 2 pixels
Un glow Kernel leave off

Abnormal Stars core and halo colour ( and diffraction spikes ) should morph or blend into a uniform colour closest to adjoining colour of star core.


Star Colour Correction using Highlight Repair in Colour module

In Colour module the Highlight Repair tool can help reduce abnormal coloured halos around stars or intense colour around stars. This tool works well in Narrowband Hubble palette SHO , HOO , OHS etc….where you can get magenta / red / blue halos
Start off with 2 pixels and increase as required.
Be cautious about high settings eg: 8 to 10 pixels as this tool can bleach our stars especially in Broadband images.

All above settings are only a guide , you may have to adjust as required

Clear Skies
Martin

[Stefan B]

Oh, I was not aware, that this is possible?! How do you do that? It was the galaxy preset with reduced Detail Size (50px) and Brightness Correlation (50%), increased Strength (150%) and reduced Gamma (0.9).

That requires a bit of cheating. You accent e.g. M 81 with the galaxy preset, go to the layer module and undo the accenting for all of the image excluding M 81 (with masking). Then you go back to NBAccent and accent with the nebula preset for accenting M 82. Afterwards you undo this accenting in layer excluding M 82.

The layer module says you shouldn't use it while tracking. I ignored that.

I found that to be a pretty efficient way for this galaxy pair since galaxy preset works well for M 81 while it's not as good for M 82 since the galaxy preset has the brightness correlation with the broadband image. But the Ha filaments of M 82 are in regions where there is basically no broadband signal so brightness correlation dims the Ha signal. Maybe you can also just fiddle with the brightness correlation until it works for both

No. Currently is pretty dry here (too dry ) and so I dared to leave the rig outside. I just covered it with the caps and a sheet in the morning.

Yeah, same here. Too dry, but nice for astro...

Regards
Stefan

[decay]

some ways to use Startools and correct issues with Star colour like Rainbow effect, bicolour halo , excessive saturated colours , narrowband colour artefacts etc…

Thanks for sharing your notes, Martin!

Best regards, Dietmar.

[decay]

Thank you for the explanation, Stefan. I understand. Maybe I will give that a try, together with Martin's suggestions. Later. For now I'm fed up with this galaxy pair

Maybe you can also just fiddle with the brightness correlation until it works for both

Yeah, I think I already tried that - with - well - moderate result. Too bad that these two galaxies are of so different appearance

Best regards, Dietmar.

[Stefan B]

Too bad that these two galaxies are of so different appearance

True in terms of processing. But it makes for a great image