NGC6744 - Reprocess

[David Fitz-Henr]

Well, the clouds have been plaguing my attempts to gather new image data, so I thought I'd have a final crack at processing my first image taken through the new scope. Hopefully an improvement on my earlier attempts.

Large Image:
http://upload.pbase.com/david_fitz_h...19166/original

Small Image:
http://upload.pbase.com/david_fitz_h...46319166/large

[multiweb (Marc)]

That's pretty awesome! Amazing.

[Stevec35 (Steve)]

Didn't see the original but that looks pretty good to me. The reddish colour cast on the galaxy doesn't look quite right though.

Cheers

Steve

[gregbradley]

Unbelievable fine detail in the galaxy. Wow, that must one sharp mirror.

Your sky background is splotchy red and blue patches. Very odd looking. You've pushed something too hard or used minimum filter perhaps.

Galaxy colour looks too blue greyish to me. It should be more a lightish blue. Its not far off though but the background is a problem.

Greg.

[Ross G]

A beautiful galaxy photo David.

So much detail and so sharp.

Great colours as well.

Ross.

[alpal]

Originally Posted by gregbradley

Unbelievable fine detail in the galaxy. Wow, that must one sharp mirror.

Your sky background is splotchy red and blue patches. Very odd looking. You've pushed something too hard or used minimum filter perhaps.

Galaxy colour looks too blue greyish to me. It should be more a lightish blue. Its not far off though but the background is a problem.

Greg.

I agree - what has caused the background to have such large
red & blue patches - it doesn't look normal - like a wallpaper pattern?
On the other hand the galaxy is super sharp & detailed.
Something has happened with the processing along the way
but I've never seen this before.

[David Fitz-Henr]

Originally Posted by multiweb

That's pretty awesome! Amazing.

Thanks Marc - this is about the sixth time I've reprocessed this and I'm getting a bit better each time

Originally Posted by Ross G

A beautiful galaxy photo David.

So much detail and so sharp.

Great colours as well.

Ross.

Thanks Ross!

Originally Posted by Stevec35

Didn't see the original but that looks pretty good to me. The reddish colour cast on the galaxy doesn't look quite right though.

Cheers

Steve

Originally Posted by gregbradley

Unbelievable fine detail in the galaxy. Wow, that must one sharp mirror.

Your sky background is splotchy red and blue patches. Very odd looking. You've pushed something too hard or used minimum filter perhaps.

Galaxy colour looks too blue greyish to me. It should be more a lightish blue. Its not far off though but the background is a problem.

Greg.

Originally Posted by alpal

I agree - what has caused the background to have such large
red & blue patches - it doesn't look normal - like a wallpaper pattern?
On the other hand the galaxy is super sharp & detailed.
Something has happened with the processing along the way
but I've never seen this before.

Thanks for the feedback Steve / Greg / Alan. I had concentrated so much on getting the galaxy right I didn't notice the background mottling - it was mostly due to using the Shadows/Highlights adjustment, trying to get all the faint detail out. I have fixed this now.
The colour has been the hardest thing to get right - I have turned up the cyan in the selective colour tool even more and I think that it looks better (red cast turned down and a more pleasing light blue cast generally).
I have loaded the latest to the original links below - please take another look and let me know what you think.

[Larryp (Laurie)]

Beautiful image, David!

[gregbradley]

Colours looks great. I find adding yellow into the cyan or blues in selective colour is what is lacking to get that lovely galaxy blue that can elusive.

That is a fab 6744, so detailed. Its not an easy target. The background looks a lot better but there is some residual blue/red splotch. Perhaps select out the non galaxy areas and use colour balance tool and turn down blue and red in the lower bands.

Greg.

[RickS (Rick)]

That's a great looking NGC 6744, David! I remember struggling with the background when I imaged it a while back.

Cheers,
Rick.

[Paul Haese]

Still blue and red blotches in the background (did you say you fixed the problem?). However the detail is sublime. Awesome detail. Get that background right and you will have a winner.

[alpal]

Hi David,
The red & blue patches are still there in the background.
I loaded it into Photoshop but I couldn't fix it because the black point is clipped.
I would have to start processing it from scratch to keep the background correct.

[David Fitz-Henr]

Originally Posted by Larryp

Beautiful image, David!

Thanks Larry!

Originally Posted by gregbradley

Colours looks great. I find adding yellow into the cyan or blues in selective colour is what is lacking to get that lovely galaxy blue that can elusive.

That is a fab 6744, so detailed. Its not an easy target. The background looks a lot better but there is some residual blue/red splotch. Perhaps select out the non galaxy areas and use colour balance tool and turn down blue and red in the lower bands.

Greg.

Originally Posted by RickS

That's a great looking NGC 6744, David! I remember struggling with the background when I imaged it a while back.

Cheers,
Rick.

Originally Posted by Paul Haese

Still blue and red blotches in the background (did you say you fixed the problem?). However the detail is sublime. Awesome detail. Get that background right and you will have a winner.

Originally Posted by alpal

Hi David,
The red & blue patches are still there in the background.
I loaded it into Photoshop but I couldn't fix it because the black point is clipped.
I would have to start processing it from scratch to keep the background correct.

Thanks for the feedback Greg / Rick / Paul / Alan. I've had another go at neutralising the background (looks better now) and have also slightly enhanced some of the fainter galaxy detail. There is some slight black clipping as Alan says and after talking with Marc (multiweb) offline it seems I have not left enough range at the foot of the histogram during the initial stretching (I reset the blackpoint after each stretch to the foot of the histogram as I have read that was the approach to use; however I found that subsequent colour adjustments can then lead to some black clipping). The mottling effect in the background was introduced when I used Reduce Noise tool in PS and I think that I set the colour noise reduction too aggressively (and too early perhaps). Anyway, it's been a good exercise to revisit this image as I have learned a lot each time I did it. I'm quite pleased with how well the actual galaxy now looks, and I may have one more go at reprocessing the whole thing from scratch in a few weeks

[Gem (Grant)]

Nice! Good job on a good target.

[gregbradley]

Yes its best to slide the black point up to close to the right hand side of the histogram but not all the way as you pointed out.

With noise reduction it needs to be selective. There is no point in reducing noise in the galaxy (unless it needs it) when the noise is in the background. All it does is reduce detail as noise reduction boils down to blurring.

Noel Carboni Photoshop actions reduce deep sky noise reduction works very well and seems to only be applied to dim regions.

Noise Ninja is very effective as well and is selective.

The mottled effect is from excessive blurring of the background colour noise.

Greg.








Thanks for the feedback Greg / Rick / Paul / Alan. I've had another go at neutralising the background (looks better now) and have also slightly enhanced some of the fainter galaxy detail. There is some slight black clipping as Alan says and after talking with Marc (multiweb) offline it seems I have not left enough range at the foot of the histogram during the initial stretching (I reset the blackpoint after each stretch to the foot of the histogram as I have read that was the approach to use; however I found that subsequent colour adjustments can then lead to some black clipping). The mottling effect in the background was introduced when I used Reduce Noise tool in PS and I think that I set the colour noise reduction too aggressively (and too early perhaps). Anyway, it's been a good exercise to revisit this image as I have learned a lot each time I did it. I'm quite pleased with how well the actual galaxy now looks, and I may have one more go at reprocessing the whole thing from scratch in a few weeks [/QUOTE]

[David Fitz-Henr]

Originally Posted by Gem

Nice! Good job on a good target.

Thanks Grant!

Originally Posted by gregbradley

Yes its best to slide the black point up to close to the right hand side of the histogram but not all the way as you pointed out.

With noise reduction it needs to be selective. There is no point in reducing noise in the galaxy (unless it needs it) when the noise is in the background. All it does is reduce detail as noise reduction boils down to blurring.

Noel Carboni Photoshop actions reduce deep sky noise reduction works very well and seems to only be applied to dim regions.

Noise Ninja is very effective as well and is selective.

The mottled effect is from excessive blurring of the background colour noise.

Greg.

Thanks Greg - yes I did apply the noise reduction only to the background but looks to have been too aggressive. I'll try Carboni's action in the next (and hopefully final) repro!