Horse Head Nebula- post processing and stars

[el_hop87]

Hi

I have still got a lot to learn with post processing and was wondering if anyone could advise on how to create the "twinkle" on large stars in images please. I am editing my Horsehead Nebula shot but the large stars look blown out rather then sharp and the typical 4 spike twinkle that you see in some image.

Please see below link to my current file, and the original file to this post - if anyone could help with this particular issue as well as any other suggestions on how I could improve, that would be very much appreciated! :

- Image so far: https://www.dropbox.com/s/9vqn9babg1ff5 ... 3.jpg?dl=0
- Original stacked fits file: https://www.dropbox.com/s/oknlpjw92uv35 ... e.fts?dl=0


For info I used a Nikon 5200, SW AZ GTI, SW Evostar 72ED and IDAS P2 filter - 1.5 hours of data at 60' subs, stacked image (DSS) is lights, darks, flats and bias.

Many thanks in advance,

Elly

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[Adreneline]

47 minutes ago, el_hop87 said:

I am editing my Horsehead Nebula shot but the large stars look blown out rather then sharp and the typical 4 spike twinkle that you see in some image.

Hi Elly

Everyone struggles to contain stars in this region - especially Alnitak. You've done very well to keep it in check. Personally I'm not a fan of introducing star spikes where none existed. If your imaging with any sort of reflector then spikes are to be expected but not with a refractor as you are using. If you really want to add spikes there are a number of plugins for the likes of PS that will add them for you.

As for containing very bright stars/regions some people go for the range of exposures approach and then combining using masks and the like in PS/GIMP etc. Some use HDR approaches as well.

I've had a very quick go at processing your master stacked image. There is quite a lot of noise which I'm struggling to contain whilst at the same time pulling out the colour. I am sure someone will greater skills than me can do much better.

HTH

Adrian

[el_hop87]

Hi Adrian, 

Thank you very much for reply! - this is really useful. I know what you mean re the stars, good to make things look as natural as possible. I hadn't realised about the star spikes being a result of a reflector, I thought they were developed in post processing (not as a new superficial creation, but as a development of existing stars in the image) - your edit is brilliant, and the large stars look much better than in mine and more detail/ shape on the horse head itself. 

Can I ask which processing software you used please? 

Thanks

Elly

 

[teoria_del_big_bang]

Hi,

Processing data is not something that comes easy and as a relative newbie I am still learning all the time and there is no easy remedy but to practice and keep practicing with lots of searching on Google for methods used in your particular software.

I found it good to borrow somebodies known good data to do some practicing then you know that the data is good and see if you can create a worthy image. Trouble I found when learning is that sometimes my data was poor and so did not help with learning how to process as the lack of strong data was making it hard for me.
There are often small competitions on SGL that give everybody the same data (maybe it might be mono not from a DSLR) but the processing is similar so that may help as you would see what others are achieving with same data and you can even ask them how they did various things.

I too have had a quick go at processing the original stack and also struggling to get any different to Adrian without getting overblown bloated stars, so whilst I am by no means competent at this I fear you may have done as well as you can with the data.

If your tracking is good enough maybe try longer exposures.

I also wonder if your IDAS LP filter also is not helping, particular with this target and is also blocking a lot of the nebulosity from the horsehead ???
How was the moon when you shot this, that could also be a factor.

If your LP is not horrendous then I would be tempted to try a shot or two without the filter to see what data you may be loosing.

What software are you using ?

Steve

Edited April 6, 2021 by teoria_del_big_bang

[el_hop87]

Many thanks for this - yes, its a great idea to practice on available data, I need to do lots more of this! 

I'm afraid 60 second exposures are the longest I can get with my current set up (even then I was beginning to get star trails)- I think that guiding would help, once I have the budget for it. It was a moonless night, but light pollution is a factor as I live in a Bortle 6 city. 

Software I am using is Deep Sky Stacker, Star Tools and final edits in Photoshop and Lightroom. 

Many thanks again for your help! 

[teoria_del_big_bang]

I think considering your conditions then you have produced a great image so do not be disheartened.

You probably do need the LP filter then but it will mean you need longer exposures as you will lose some of the nebulosity as well as filtering the LP.

Steve

Edited April 6, 2021 by teoria_del_big_bang

[el_hop87]

Thank you Steve- thats kind of you to say. Its a steep learning curve but really loving the experience so far. 

Thank you for all your help! 

Elly

[Adreneline]

1 hour ago, el_hop87 said:

Can I ask which processing software you used please?

Hi Elly,

Like a lot of people I use several different software packages. I tend to pre-process in AstroPixelProcessor because I like the interface - it's a bit like DSS in some respects. I tend do all my main post-processing in PixInsight, certainly noise reduction, background extraction (i.e. gradient removal) and stretching to non-linear. I use Affinity Photo for cosmetic adjustments - getting rid of little blemishes and enhancing colour selectively (I used to use PS but as CS6 no longer runs on my Mac I've moved to Affinity). I use Dfine2 (a very old free version) to do a final bit of noise reduction on some images, but not all.

I think once you've pre-processed (calibrated, registered and integrated) then the "less is more" approach is often the best; it's too easy to go too far in search of that last photon.

Finally as Steve has already said there is no substitute for lots of data - the more the better!

Good luck.

Adrian

P.S. I used to use an IDAS UV/IR cut filter but gave up on it sometime ago. I now use Astronomik L2 (with osc camera) and L3 (with my mono camera) filters and find they are much kinder to my data. I'm sure others have different views and experiences.