Thor's Helmet: NGC 2359

[batema (Mark)]

Hi,

I'm almost crying posting my Thor's Helmet so close to Marcus's wonderful image but here we go.

This is purely an RGB image consisting of Red data 5 hours and 15 minutes, green data of 4 hours and 30 minutes and Blue being 4 hours all 15 minute subs binned at 1x1. My 21 hours of Luminance data 20 minutes subs at 1x1 just seemed to blow out the star field to become really dominant and I don't know how to solve that so the nebula can be revealed so decided to scrap in until another day and hopefully some advice.

The RGB data is all binned at 1x1 so maybe not so bad but I would somehow like to make my luminance data the star and colourise it with my RGB data.

Link to my high resolution Flickr image: https://www.flickr.com/photos/134809...posted-public/

Scope TEC 140
Mount Astrophysics 1100gto
Location Ayers Rock Yulara

Advice most welcome.

Mark

[marc4darkskies (Marcus)]

This is a lovely image Mark and if you've got another 21 hrs of lum as well you're probably sitting on the makings of a beautifully deep image! Preventing star blow out is straightforward (but sometimes fiddly) if you can layer, create masks, apply non linear stretching and do some star reduction (as in Photoshop). What software do you use?

[Atmos (Colin)]

It is a lovely image even without the extra luminance. Although I am pretty terrible at doing it, I believe it is largely about creating a good star mask and then performing the stretching, keep the stars as they are while bringing the faint nebulosity out.

[batema (Mark)]

Thank you Colin and Marcus. I acquire my images using MaxIm V6, stack my images in the old faithful Deep Sky Stacker so all channels are aligned and have not had an issue with this method except for my horsehead that wouldn't align my hydrogen alpha. For processing it is photoshop CC from the cloud with everything. If you could briefly outline a process that would be wonderful. I do know how to use masks, invert them as well as the other basics. Still sooooo much to learn.

Thanks

Mark

[RickS (Rick)]

Nice colour and quite a decent image, Mark. If/when you come over to the dark side (PI) I can offer advice, but my PS skills are only newbie level.

Cheers,
Rick.

[marc4darkskies (Marcus)]

Originally Posted by batema

.... If you could briefly outline a process that would be wonderful. I do know how to use masks, invert them as well as the other basics. Still sooooo much to learn.

Thanks

Mark

Brief it is! If you download this PDF, you'll see before and after screenshots of my quick fiddle with your image showing the high level steps. It at least illustrates at a high level a standard part of my workflow to tease out faint detail while minimising star bloat.

https://www.dropbox.com/s/6fwcwyc7t0...Thors.pdf?dl=0

Basically:
1) generate a rough starless version of your image
2) use the starless version as a layer mask for whatever tool you want to use to brighten the neb (I used a simple curve). This will apply most of the brightening to the neb and not the stars or the background (although there will be some bleed)
3) Do a real unsharp mask to restore some nice contrast to the core
4) Decrease your star sizes to compensate for some increase caused by step 2.
5) Create a star mask
6) Tidy up with star masked levels - removed green cast and darkened the background a tad after a bit of brightening from step 2

There are probably other ways to do this but I have a library of PS actions that make quick work of it. There's always some tweaking regardless to get the result just right.

Cheers, Marcus

[batema (Mark)]

Thank you Colin and Marcus. I will have a crack at it tomorrow.

Mark