The best order to process a DSO

[Moonshed]

After a couple of months of wild swings between cussing and marvelling I am beginning to get somewhere with my processing, just a hint of progress. It has got me wondering what order the more experienced amongst us do their processing after stacking, I feel it may well provide some useful hints and tips. For some reason I always seem to begin with the Curves, but perhaps that should be the last? Anyway, would love to hear. Cheers.

Keith

[cjdawson]

I think this really depends on the image rather than a set procedure to follow.

That said, my first thought would be do the huge image wide things first - gradient removal and stuff like that.

then the curves and levels.  - lots of little incremental steps to tease out the data without overdoing things too much.

Then the finer stuff, stopping stars blooming teasing out extra detail in nebulosity etc.

 

That's my first thought.  I'm sure there are others and other ways of doing things.

Of course, whatever processing you do, make sure to keep the originals. And make notes on what you did as well, just in case you want to repeat.

[CraigT82]

I'm brand new to DSO processing, having only ever tried to process a couple of widefield shots before... but here's my workflow anyway!

Check image is 16 bit. change if not.

Crop edges if needed.

Check Histogram for each channel. align if out of sync.

New layer - Apply curves and levels alternatively in small amounts. Don't clip when setting black point.

New layer - play with saturation/vibrance.  Selectively saturate using sponge tool on nebula etc...

New layer - run gradient xterminator (not sure if this is actually the best place to do it?!)

New layer - apply noise reduction three or four times until happy

New layer - apply gaussian blur (just a hint) to further smooth the image.

Done!

 

I haven't yet learned how to use masks ect... will need to soon I expect

[D4N]

It depends what software you're up are using, some processes work best whilst the image is still linear so those get done first.

With PI the screen transfer function is nice as it gives you an idea of how the changes will effect the image once it has been stretched but doesn't actually apply the stretch to the data.

[Moonshed]

Thanks for the info guys, it is much appreciated. I have PS for processing. I will probably add Gradient Exterminator soon as well. The one I had in mind is M31 because as I try to tease out the feint detail in the arms I end up with a horrible bright sky with a feint bright area over the  whole galaxy. As I darken the sky to a more natural shade I can see the detail fading away. All very frustrating.

[rubecula]

I can't claim any credit for this, I found it on the Youtube Astrobackyard channel:

Assuming DSS output, developed with Photoshop and Noel Carboni's Actions

1. Crop image slightly to remove stacking overlaps

2. Image – mode 16bit HDR Toning to Exposure & Gamma

3. Gradient Exterminator

   1. lassoo DSO, invert selection

   2. run Exterminator from Filters

4. Check and adjust levels

5. Curves initial stretch using 2 points to produce smooth curve

6. Noel's “Local Contrast Enhancement”

7. Noel's “Enhance DSO and Reduce Stars”

8. Redo Curves – use control/click to register black area on graph and another in nebulosity, raise the spot in the nebulosity to brighten the DSO

9. 2 x Noel's “Make Stars Smaller”

10. Noel's “Less Crunchy More Fuzzy”

11. Noel's “Space Noise Reduction”

12. Levels – use middle dropper to select dark area, move black point to histogram

13. Finally adjust vibrance

Sometimes the images can be improved further by tweaking in Lightroom.

HTH

[bottletopburly]

I gave up  on PS personally to frustrating faffing about ,now use Startools lot simpler no need for addons  all the tools i need are in the box ,mastering it`s  another thing but i can get good enough results that im happy with and costs about £30 ish  

[Moonshed]

HTH Many thanks, that looks most useful, I shall definately be trying that tomorrow and looking forward to seeing the results. The only thing on there I don't have is Grdient Exterminator and as I have been meaning to get it I will get it first thing in the morning. If the results are good I will post them, if not I will just keep trying until they are good.

Cheers. Keith.

[Moonshed]

Bottletopburly. Hi there, I am surprised that you are unhappy with PS, I find it a very good programme and have been using it for over twenty years now. I appreciate that parts of it, parts I have yet to learn, (layers and Curves for example) can seem a bit frustrating to use but when you consider the amazing job PS does this is not surprising. However, we all have our own ways of doing things and therefore some programmes are better suited to us than others, but PS does satisfy a lot of people. Cheers. Keith.

[bottletopburly]

45 minutes ago, Moonshed said:

Bottletopburly. Hi there, I am surprised that you are unhappy with PS, I find it a very good programme and have been using it for over twenty years now. I appreciate that parts of it, parts I have yet to learn, (layers and Curves for example) can seem a bit frustrating to use but when you consider the amazing job PS does this is not surprising. However, we all have our own ways of doing things and therefore some programmes are better suited to us than others, but PS does satisfy a lot of people. Cheers. Keith.

Yes i have no doubt Ps is a top program but i just havent got the time for messing around and buying add ons here and there ,when theres simpler soloutions  avaliable  ps im lazy lols 

 

[Moonshed]

4 minutes ago, bottletopburly said:

Yes i have no doubt Ps is a top program but i just havent got the time for messing around and buying add ons here and there ,when theres simpler soloutions  avaliable  ps im lazy lols 

 

You raise a good point. As I said I have had PS for over twenty years and back then, even though it was expensive, it was affordable for most people. I am not so sure today, indeed it has become so expensive I believe you can take it on a monthly rental. That being the case it really shouldn't be necessary to buy add ons. I totally agree. Cheers. Keith

[Uplooker]

I like your thread and the comments so far. I am no good at processing, at all! Although I am not able to play the piano, nor any instrument, I can tell when someone is playing it well, or not.

It is clear that people have different ways of doing things, that is most certainly true for processing.

I believe that there is no set way or order to do any of it, its dependent on the subject and or the quality of the data.

I am still interested in the responses, although may not have anything to add, just interested in the responses ?

[mikeonnet]

I am a novice myself in this AP game but have defiantly caught the bug knowing the fact that the images taken are all from my own equipment and work and even though they’re not by any means stunning (although I impressed myself with M31 the other day), I appreciate the images in the knowledge of "I took that!".

 

I find when stretching the images, I get quite bad vignetting and I am hoping to build a lightbox this weekend (using white LED strip and Opal Perspex to difuse the light) as I only have Gimp and therefore do not have the Xterminator app to remove the vignetting.

If you haven't come across it, there are "Excellent" tutorials on YouTube by Doug German (just search his name) that covers all the Post processing techniques Although he uses PS, a lot of it is similar in Gimp. It's a must see in my opinion as he explains everything clearly and in detail and the purpose of why he is doing it (rather than lots of tutorials that just say, click here, lower this setting, then click here and so on.....not providing a reason for "why" I'm having to click this button for instance.

[Moonshed]

Mkeonnet, Hi, I agree that there is nothing so good as taking your own images of the amazing sights in the night sky, they may not be brilliant but they're yours. I have come across Doug German on YouTube and have a couple of his excellent tutorials stashed away on my Playlist and have every intention of watching them today, notebook in hand. Once I have done that I will revisit my images and re-process them in Photoshop to a, hopefully, better standard this time. Regarding your comments on your  M31 image, the first time I saw that image appear on my camera screen taking the first of 30 subs. I felt almost overwhelmed, it was just so amazing to think that there I was in my back garden, looking at an image I was taking of a galaxy over two million light years away! A wow! moment for me. And all the equipment was actually working! Cheers. Keith.

[wornish]

One tip I have picked up from watching tutorials is - first crop out any stacking artefacts otherwise you are limiting the dynamic range of the image, you can see them if you do a temporary exposure increase  or a stretch on a copy of the image to see where they are.  Then remove the temporary stretch and do the noise reduction steps of your choice.  Otherwise when you come to doing the permanent stretching you are stretching the noise as well which makes it much harder to remove.

 

 

[Moonshed]

Thanks Dave, that's a useful tip, I shall do that.

[ollypenrice]

You should certainly crop off edge artefacts first. Nobody is going to disagree with that - even on here!

Next, it is important to set the end points in levels. The data lines must reach right the way from left to right. Again, not controversial. Bring in the black and white points to meet the data if necessary but don't clip!

My next step for an RGB layer is DBE in Pixinsight to remove gradients and obtain a good colour balance. I'll usually use SCNR green at this stage as well. Next stop Photoshop.

I'll stretch in Levels by moving the mid point left, or in Curves, depending on the layer. RGB always in Levels, Ha always in Curves, Luminance either, depending on the target. (The more faint stuff there is the more likely I'll stretch in Curves.)

Now, stretching in Curves. Some say softly softly and some say Whack it!  I'm a whacker, certainly in Ha. I demo this regularly in my tutorials and compare the results. An aggressive Curves stretch gives far more low level contrast than a mousy log stretch. This...

gives you this...

which then needs the black point resetting.

I'll stretch to the noise limit or a tad beyond it then apply NR only to the bits which need it.

From here on in, I have no fixed approach and urge myself and others to look at the picture  because the picture will tell you what it needs. I really believe strongly in this, but we all need to learn how to look at the picture properly.

Olly

 

[Moonshed]

Thanks Olly, that is very informative,  I appreciate your advice.

[Astrosurf]

Great stuff here! I'm always learning. For those objects like M31 and M42, with high dynamic range, use this masking technique:

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

I tend to start using Levels in a few short iterations. I don't touch the RH slide, only the middle and LH ones, and keep some space between the LH one and the start of the curve. Then I use Curves and back to Levels repeatedly to check if I'm not clipping or getting posturisation. 

To keep the stars from getting blown out, I place to alignment points close together at the white point part of Curves - see attachment (for RGB - the bottom part for mono). I also use the Magic Wand tool to iteratively deselect the stars from the processing. Ask me how to do this if you don't know.

To bring out colour I sometimes do a copy layer and convert the Blending Mode to Colour. Then tweak it using Hue & Saturation or Colour Balance. Then G Blur

The rest is a mixture of tools, especially Noel Carboni's, and lots of frustration!

Alexxx