Star removal/reduction in veil nebula

[BrendanC]

Hi all,

So I've captured about 11 hours' worth of the Eastern Veil Nebula. The actual nebula looks lovely - but, to quote Dave Bowman, 'My God, it's full of stars!"

I have a strong feeling most of the 'starless' veil images I've seen are taken using filters that just capture the nebula, not the stars.

However, given that I don't have filters, I've tried several post-processing techniques - using the Photoshop colour picker/feathering/filter method, StarNet, StartTools's 'heal' feature - and none of them really work.

Should I just accept that it's a very difficult object to image without filters, or does anyone know of any other approaches that might work? Ideally using Photoshop, StarTools, or some free software ie not shelling out for PixInsight etc.

Thanks, Brendan

Edited September 23, 2020 by BrendanC

[Kinch]

30 minutes ago, BrendanC said:

I have a strong feeling most of the 'starless' veil images I've seen are taken using filters that just capture the nebula, not the stars.

No - I don't believe there are such filters that any amateur is using.

I see you have tried StarNet - surprised that did not work for you. Perhaps you can find another programme that I remember: Straton

I am not sure if that is a free programme or not - I have not tried it in years.

Edited September 23, 2020 by Kinch

[Seelive]

I'm having exactly the same problem, there are so many stars in the field. I can't get Starnet to produce a usable starless image either. A work in progress, I'll certainly be interested if you find a solution.

[BrendanC]

@Kinch - interesting, I just assumed that certain narrowband filters would help during acquisition. So, if not, then presumably the beautiful shots I've seen, with the nebula standing proud of the stars, and intact, were all achieved in post processing? 

I'll give Starnet another blast and look for that other program you mention, but I am still intrigued as to how those images are achieved! 

 

[Kinch]

Yes - in general the stars are smaller via NB filters, most especially in the Ha. But as you see, this area is awash with stars and the best you can do is to reduce their overall impact on the image i.e. make the nebulosity stand out. Some areas are much harder than others and the veil is definitely on the hard half of the list.

 

This is mine from just over a year ago -  not the best but at the time, I was happy enough to get a finish on the images - because if you overdo it (star reduction) ...then the stars start looking like noise.

https://www.kinchastro.com/veil-nebula.html

[Adreneline]

2 hours ago, BrendanC said:

does anyone know of any other approaches that might work? Ideally using Photoshop,

I have found the reduce star size action in Annie's Astro Actions for Photoshop works well - at $15 they are a bargain with lots of useful actions. This particular action is quite subtle and on occasion I have used it several times on the same image. I have also used it on individual filter masters (mostly OIII) to reduce bloating before combining - it is a very effective method of reducing those annoying blue halos (it also works a treat on B in RGB processing) and seems to have no impact on the underlying nebulosity. It was a good fix when imaging with a cheap doublet!

Adrian

[BrendanC]

@Kinch - great image, and thanks for the advice. Looking at my original 'reference' image (https://astrobackyard.com/ngc-6992-eastern-veil-nebula/) I can see that he also has stars albeit reduced.

@Adreneline - interesting, I've come across these kind of packs before but being fairly used to Photoshop, I tend just to follow tutorials and use my own experience to try these techniques. I've tried following the steps at https://photographingspace.com/star-reduction/ without much success, and they also have an action set. But yes, I've also heard about Annie's pack, so perhaps I should invest in that. I just need to confirm it works with my VERY dated version of Photoshop (CS2). Ideally I'd do everything within StarTools, but I often just touch things up in Photoshop at the end.

Thanks all. Looks like I chose a 'toughie' this time!

Edited September 23, 2020 by BrendanC

[happy-kat]

You can shrink stars in Startools

[BrendanC]

@happy-kat Yep, thanks, tried that too (the 'heal' module) but it's not really cutting it for me I'm afraid. At the end of the day my image might even just be too noisy (it's from a DSLR). I'm currently re-stacking it with some different calibration files to see if that helps, then I'm going to try everything I can think of (again!).

Edited September 23, 2020 by BrendanC

[BrendanC]

OK, so here we go, I remember all this now from when I started out...

Which is best: Annie's, Carboni or Starizona? They're all very similar in price. Any votes?

[Adreneline]

I have A and C and use A the most; not used S.

 

 

[happy-kat]

1 hour ago, BrendanC said:

@happy-kat Yep, thanks, tried that too (the 'heal' module) but it's not really cutting it for me I'm afraid. 

not the Heal module, that can be used to remove stars

the Shrink module can be used to shrink the stars of our choice (mask)

[almcl]

To amplify Happy-kat's point about the shrink module, here are two versions of the Eastern Veil, post processed only in StarTools.  They are from a bi-colour (Ha +  Oiii) filtered set and the second one has used the shrink module at 30 iterations to 'tone down' the stars - rather more than I am really happy with but just to show what is possible. (It's a work in progress as am debating adding some RGB star colour)

 

Edited September 23, 2020 by almcl

[happy-kat]

I also thought to add that the mask plays a key part in the Heal module and you may find you have to grow the star mask and then try again and adjust the mask again if not enough, there's also the mask fuzz adjustment.

[BrendanC]

Excellent, I seem to have completely overlooked the shrink module. Will give it a go although there's no way my attempt will ever approach the examples above which are stunning. Thanks again! 

[carastro]

I have found that using the star shrink actions, seem to affect the nebula as well if you do more than one iteration which is sometimes necessary.  then recently I found it works better if you select just the stars and feather then before you perform the action, it then only affects the stars and not the nebula.

I guess you would call that a star mask before performing the action.

Carole 

[BrendanC]

Thank you! Lots of approaches then. I'm going to try them all over the weekend. One of my favourite things - just spending ages getting images to look nice.

[BrendanC]

Hey, the star shrink in StarTools worked really well! I found the 'tight' setting was best, bit of masking, fiddling around with the settings, really huge difference. Thanks everyone.

Before/after shots...

Needs more work on the background gradients but there is much more definition to the nebula now.

 

Edited September 24, 2020 by BrendanC

[ollypenrice]

There are no star-removing filters, as others have said, though tight NB filters drastically reduce star size. Still, you want broadband star colour so that's not the solution.

The thing about post processing, where you can reduce star sizes, is not to look for one magic wand.  It's all about patience and small iterations, one small improvement at a time, often in layers. (Fight with masks in Pixinsight if you like but they are not for me.) Careful use of Curves in stretching also helps. There is no point in stretching anything brighter than your brightest nebulosity, so identify that point in Curves and don't stretch above it. It really is all about tiny steps, there is no One Big Fix. For all that, the image with which I'm the least satisfied in my collection is the Veil, despite every effort!

Olly

[Xiga]

18 hours ago, BrendanC said:

Hey, the star shrink in StarTools worked really well! I found the 'tight' setting was best, bit of masking, fiddling around with the settings, really huge difference. Thanks everyone.

Before/after shots...

Needs more work on the background gradients but there is much more definition to the nebula now.

 

I completely agree with everything Olly said. It really is all about baby steps - doing lots of small changes, rather than 1 big one, at a go.

FWIW - I actually much prefer your first image above. The broadband stars look lovely, they really shine and bring lots of colour to the image overall. If it were me, I would only reduce them slightly. Whereas with NB images of this target, the stars usually don't have any meaningful colour, so reducing them by a larger degree is more acceptable.

[alacant]

19 hours ago, BrendanC said:

StarTools worked really well

Hi

Nice shot. StarTools is definitely the way to go these days.

I think maybe you're getting overwhelming stars because you used Develop rather than AutoDevelop for the second pass after Wipe. Or maybe you missed out wipe altogether. The power of StarTools is that your data remains linear with your work held in a database so you can perform processing tasks in any order, but of course missing them out will lead to unusual results.

try

AutoDev

Bin

Crop

Wipe 

AutoDev

With the second AutoDev the one used to tame the stars. IMHO you have probably overdone the second Dev stage.

Post the stack if you like.

Cheers and HTH

[BrendanC]

@Xiga Interesting that you prefer the original! I thought the stars were far too prominent. The reduced-stars version is much closer to other examples I've seen. I really wanted to show the nice, twisty-turny nature of the nebula. The best shots I've seen really get across the idea of it being the outer edge of the nova, almost like large, semi-translucent bubbles.

@alacant Thanks, I'll give this another try following your workflow recommendations. I'm still unsure what to make of StarTools. Sometimes it works great, other times not so, and there doesn't seem much 'wriggle room' in between. It definitely brings out much more than I've ever managed in Photoshop however. I've currently got the Pixinsight demo and it's just mind-blowingly complicated.

[Xiga]

2 hours ago, BrendanC said:

@Xiga Interesting that you prefer the original! I thought the stars were far too prominent. The reduced-stars version is much closer to other examples I've seen. I really wanted to show the nice, twisty-turny nature of the nebula. The best shots I've seen really get across the idea of it being the outer edge of the nova, almost like large, semi-translucent bubbles.

@alacant Thanks, I'll give this another try following your workflow recommendations. I'm still unsure what to make of StarTools. Sometimes it works great, other times not so, and there doesn't seem much 'wriggle room' in between. It definitely brings out much more than I've ever managed in Photoshop however. I've currently got the Pixinsight demo and it's just mind-blowingly complicated.

Hi Brendan

It's true, they are too prominent in the original, but probably not by as much as you think. The black point in the 2nd version is probably slightly on the low side too. There is a lot to like when it comes to the stars that Newts produce (what with their larger aperture compared to most fracs). If you reduce the stars too much, then you lose much of their appeal imho. Btw, clicking on your image just brings up a black screen on my computer for some reason.

The other versions you've seen are most-likely all NB images. NB is good at separating out the nebulosity from the stars and background, but seeing as this is a Broadband image that you have captured, I wouldn't go chasing the NB look too much, and just embrace the star field (which is gorgeous) as it is. You can always come back and shoot it in NB another time for a completely different image! Shooting in NB drastically reduces the star sizes at the point of capture, meaning Starnet can work it's wonders at removing them. Asking Starnet to remove a star field awash with broadband stars is just never going to work unfortunately.

For star reduction, Annie's one is quite good I do find (you can always reduce the Opacity if you find the 1st or 2nd pass is too much). Alternatively, Images Plus (which is now free to use) has a good one-click (if you like) star reduction routine which I've been using lately.

[BrendanC]

Great advice, thank you! 

I have zero idea why clicking the image produces a blank screen. I just chucked them into the post and assumed the forum code would make it all work automagically.

I totally get what you're saying about the star field. I like Newts too! Those funky diffraction spikes. The broadband colours really come out with the extra integration time and StarTools magic. However, I do just really like the narowband images I've seen, and that's what I was trying to get.

I was going to look at Images Plus but I got a security warning on the website a few days ago, but that seems to have gone now. I might give that a blast too, as it's free. My main problem with Photoshop packs however is that my old CS2 Photoshop version doesn't have the sub-pixel setting and the 'preserve roundness' option for the Minimum filter used, and I'm really not prepared to pay £250 a year for Photoshop. I'm trialling Pixinsight and experiencing the same giddy learning curve other people have, so that's another digital toy to play with this weekend.

[happy-kat]

If you get to the end of that trial if you decide to trial anything else there is affinity photo or paintshoppro or even app. Though none of which can run Photoshop actions.