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Difficult Nth America Nebula

Astrosurf

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Astrosurf

Astrosurf

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I'm having real trouble stretching my Nth America nebula image. It's so dark after stacking that it ends up posterised if I keep pulling out detail. I've attached the stretched image. The stars are also too hard, but I can't get it right.

I was only using Curves and Levels very slowly and carefully.

Here's a Dropbox link to the 58Mb TIFF if you want a go!

https://dl.dropbox.c...ula Stacked.TIF

Please let me know what you did.

Alexxx

post-1704-0-38208100-1344691861_thumb.jp

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squeaky

squeaky

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Hokay.... :)

The left panel is from Images >> Adjustments >> Equalise, which shows that you have LOADS of data there. The right hand panel is from working with the exposure option. I did exposure up to 6 and about .0035 gain to get that. From there maybe you can work with levels and curves...

post-23222-0-30303700-1344804646_thumb.p

A quick and dirty way to get some meat to start with is to copy the equalised layer and combine it with the other exposure image as a layer at 50% (Had to this as a JPG because of file size limits here)

post-23222-0-23428400-1344805467_thumb.j

It would probably be better to be rather more gentle than I've been here... but anyway it's a way to get a start.

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steppenwolf

steppenwolf

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Hi Alex, there is more data in there but it is a little noisy (perhaps moisture high in the sky?). I've had a quick play with your data and produced the following image.

I started by gently stretching your image in 'Levels' - I did this in several iterations. Next I made a greyscale copy and gently sharpened this to use as a false 'luminance' channel.

I boosted the saturation of your colour image and then made a new copy that I converted to 'Lab mode' and increased the contrast of the 'a' (red) channel. I then pasted this on top of the colour image and adjusted the opacity to get the right balance. I finished the colour image with a 'Curves' adjustment to boost contrast while holding the black background down but not too dark. Finally I pasted the false luminance channel I made earlier on top of the colour image and set its mode to 'luminosity'.

I think part of the problem with your original processing was trying to get the background too black.

post-1029-0-48606000-1344806286_thumb.jp

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squeaky

squeaky

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:) Must admit that I find equalising a useful device to show me what's there in terms of faint background detail, but I don't normally use it as a layer. I've done a gentler version and included a bit of star shaping because the originals are a bit oval but it would still need work as you can see...

post-23222-0-57803700-1344808126_thumb.p

EDIT: Maybe upping the exposure a bit and then doing your magic would be the way...?

<sigh> No matter how much I learn there always seems to be a whole lot more!

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squeaky

squeaky

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Wow! Thanks guys. This is amazing. I just wish I understood what you did. As I keep saying, I have to read the manual. But it would be so much easier if I could be shown. Roll on another imaging day!

Okay... here's an easy start - then you'd need to go back to Steve's post and work through it from scratch having got some idea of the stretching.

Choose the levels menu...

post-23222-0-17663800-1344862506_thumb.j

You'll see that your "dark end" is very close to the zero, so leave that alone for now and just use the middle slider towards the curve a BIT...

post-23222-0-74684200-1344862604_thumb.j

Repeat this several times and you'll see your nebula begin to show. The histogram will also be moving towards the right. Once the gap from the "dark end" is quite wide you can now stretch both ends...

post-23222-0-12219400-1344862785_thumb.j

Again, only a little bit each time, and make sure there's always a gap between the pointer and the curve.

You'll notice that you have a very dark edge to the image (top and right) so crop the image to lose this. (it's a result from your stacking, no big deal)

post-23222-0-84378600-1344862910_thumb.j

Keep doing little stretches until you can't really move the sliders without getting into the curves.

post-23222-0-05900100-1344863007_thumb.j

Now choose Hue and Saturation...

post-23222-0-89782300-1344863047_thumb.j

Maybe a couple or three (your choice) and then do one for the red channel only...

post-23222-0-82516800-1344863133_thumb.j

It needs a bit of sharpening. I've used three iterations for this. First make a duplicate layer and then choose high pass sharpen

post-23222-0-22105100-1344863205_thumb.j

Lift the slider until you can pretty much see your whole image...

post-23222-0-26630400-1344863283_thumb.j

Your image will now look very gray! No problem - change the mode to Overlay

post-23222-0-28790100-1344863343_thumb.j

And the result is...

post-23222-0-65850000-1344863390_thumb.j

Flatten the image, Duplicate again, choose high pass, and have the slider at about 6 to 10, and change the mode for this one to soft light

post-23222-0-51082500-1344863482_thumb.j

Repeat the last few options but this time have the slider at 2 to 4 and again the mode at overlay

post-23222-0-76510800-1344863567_thumb.j

Zoom well in and you'll see that the nebula has gone a bit grainy

post-23222-0-04394400-1344863882_thumb.j

because while we've lifted the faint stars with those last two sharpens we haven't been too kind to the nebula. So choose Surface blur...

post-23222-0-67845400-1344863686_thumb.j

Use both sliders to get the background blurred without clobbering your faint stars too much...

post-23222-0-86459300-1344863747_thumb.j

And there's your start:-

post-23222-0-52884200-1344863956_thumb.j

You'll have noticed in the close up that your stars are a bit oval - so in truth it would be better to reshape those before doing any of this. Track back through my recent posts and you'll find links and help.

Once you've got the hang of this, (I've done a picture post on curves too, recently)... then you can throw all this lot away and work through Steve's top approach! :)

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Steve Ward

Steve Ward

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Evening Alex ,

I hope you don't mind me having a play with your image .

I didn't use PS here , merely the Adjustments available in DeepSkystacker that appear at the end of the stacking process when the final image is displayed.

NthAm1-CopyPNG.png

I know that 'everyone' uses Photoshop , but I just wanted to show that those of us like me who don't possess , or get on with PS can still get plenty out of an image .

My M31 was done with the same adjusters.

Thanks,

Steve.

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Ewan

Ewan

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Really useful 'tutorial' for a lovely image, I have cs6 & will be trying these tips out.

Not hijacking your thread here but my stacked subs look BW instead of colour ie my M31 (even though I shoot colour) is it best to pull R G & B channels through as individual layers then flatten. Nice AP again Alex ;-)

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squeaky

squeaky

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Evening Alex ,

I hope you don't mind me having a play with your image .

I didn't use PS here , merely the Adjustments available in DeepSkystacker that appear at the end of the stacking process when the final image is displayed.

<image>

I know that 'everyone' uses Photoshop , but I just wanted to show that those of us like me who don't possess , or get on with PS can still get plenty out of an image .

My M31 was done with the same adjusters.

Thanks,

Steve.

YEP

Lifting the histogram first in DSS would save a lot of those levels iterations in PS.

It would then only need the star shaping, a bit of a tweak on curves, and a touch of sharpening.

Astro... have a browse and read of the pages on the DSS web site for how to get the best out of your stack before moving on to post processing. :)

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squeaky

squeaky

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Once you're happy with the basics there are all sorts of tutorials out there that can really help you to get the best out of your images. The stuff I've posted recently really is a simple "starter for ten" - as you'll see when you start tracking down videos by the real pro's :)

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squeaky

squeaky

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Here's a quick PixInsight process for comparison.

Background Gradient Removal (DBE)

Colour Calibration

A quick stretch and saturation boost.

unsharp and Noise Reduction

Nice. Just goes to show that there's no "one way" or one "right way" to process an image. We have, what?, four different approaches here, all of which produce very similar results and it's really down to the image owner to decide how they want their final result to look.

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GlassWalker

GlassWalker

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Have my interpretation, also using PixInsight.

Rough process: crop the borders, dynamic background extraction (manually since there's so much stuff you want to keep in this one), histogram transfer function. At this point, transfer to Photoshop Elements, then: further tweaks to levels, noise reduce, reduce stars (dust and scratches). Fine tune contrast and saturation.

I also like PixInsight, but the learning curve is quite steep. I think I'm over the worst of it now, but there's still so many functions I haven't touched yet...

post-22006-0-34120800-1345068289_thumb.j

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Astrosurf

Astrosurf

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You're all having fun aren't you! This is great.

I've had a go myself but just don't seem to have the knack. I'll combine all I've learned and do what I feel instinctively. I'm also searching the Web for tutorials.

Let's have an intermediates' imaging day! I can bring all these pics and have a go.

Thanks for all your help guys!

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