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NGC 7635 - Hubble Bubble Nebula

x6gas

By x6gas
in Imaging - Deep Sky

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x6gas

x6gas

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Great to see the images roll in during this fine weather!

I've been sticking to one target and collecting data on NGC 7635, the Bubble Nebula. I now have some Ha, OIII, and SII data so here is a narrowband rendition in the Hubble Palette.

As soon as I started to process this, I realized that I need longer subs for the OIII so I think I will capture some 15 minute subs for that and see what happens. I've had real trouble getting the background colour to look right and I'm still not happy with it - it looks too reddy-brown but I'm having trouble fixing it...

Scope: 11" EdgeHD @f/7 w/ Celestron 0.7 reducer

Camera: Atik 490 ex, binned 2x2, 2" Baader filters

Mount: CGEM DX

Guiding: Atik OAG, QHY IMG0H, PHD ~ 0.6 rms

Ha = 23 x 600s, O[iII] = 21 x 600s, S[iI] = 10 x 900s

gallery_11821_2457_614464.png

As always, suggestions for improvement very welcome!

Thanks for looking, Ian

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Martin-Devon

Martin-Devon

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Very nice delicate processing Ian, the blue hues especially have come out really well in the bubble itself. I've also had these reddish-brown colours as well in some of my narrowband images and despite numerous attempts with moving the selective colour sliders all over the place, I've not managed to transform them to a better outcome - so if you manage to get to the bottom of this, please let me know how you did it!

Martin

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x6gas

x6gas

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Wonderful detail in the bubble! Stars look a bit blurry for my taste, and perhaps there are ways of removing some of the halos, but a great image anyway,

E.

Thanks Epicycle. Yeah I am pleased with the detail in the bubble too - I've spent some time processing the Ha and that's showing a lot of promise; I'll probably post that later.

Yes... blurry stars. I really struggle to get these narrowband images sharp. I do have a slight Gaussian in here and the sharpening is only in certain parts of the nebula. I've also stretched the data a bit too much - especially the OIII, trying to make up for having subs that are too short. I'm going to try reprocessing the data and protecting the stars using a mask or star layer. Of course the transparency wasn't great when I took most of this but I'm also concerned by the star shapes bottom right. Maybe I still don't have the spacing right on the reducer or there is some tilt so I'm going to run some images through CCD Inspector to see what's going on.

The halos I personally am less bothered about at the moment, especially since they're shining through nebulosity...

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x6gas

x6gas

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I really like the detail in this - Colour wise, I *think* it's a little green. Have a try running it through HLVG or SCNR in PI. I bet that will give you a slightly happier background as well.

Thanks Sara. Yes, my age old problem. I've no idea why but my mointor at home and on my laptop show this as being very much gold, but on my work monitor it is defintely yellowy-green and quite unpleasant. I did as you suggested and ran it through HLVG and will post that later.

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x6gas

x6gas

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That's lovely :) Yes, could do with more data but a great start :) As for colour I follow these instructions - http://bf-astro.com/hubbleP.htm Seems to work pretty well.

Hi Gina - yes I do follow Bob's process - though on this image I found I needed to leave out the final two tweaks of the cyan as it basically over saturates the blue otherwise. I only have 10 subs of the SII and would like more but it is the OIII that is really letting the show down. I've pushed it way too far and so will try to get some 15 or maybe 20 minute subs - hopefully tonight.

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x6gas

x6gas

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Very nice delicate processing Ian, the blue hues especially have come out really well in the bubble itself. I've also had these reddish-brown colours as well in some of my narrowband images and despite numerous attempts with moving the selective colour sliders all over the place, I've not managed to transform them to a better outcome - so if you manage to get to the bottom of this, please let me know how you did it!

Martin

Thanks - as ever - Martin. I've been spoilt a bit this year and the LRGB images I've taken really haven't needed much processing at all. I find I have to work a lot harder on the narrowband... and I seem to have forgotten a lot of stuff! I actually tried to do a reprocess of the Pacman Nebula that I took last year because I've never been happy with it, but can't get it anywhere near as good as I manage then, let alone better! It's also a case of getting to know what the target and the data responds to so I will be doing at least one full reprocess of this and possibly a narrowband enhanced RGB too.

As for the brown background... It's hard because there is nebuosity across most of the background. You would think that what's needed is to increase the green a bit and the blue by a bit more but like you've I played with the selective colours and can't getting looking right... and I don't like it jet black... I'll keep trying!

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x6gas

x6gas

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Nicely done Ian,

Great details around the bubble and the target itself looks wonderful. Like Sara I would prefer less greens but it's matter of taste here.

Mark

Thanks Mark. You're right it is a matter of taste - especially with false colour images - but this looks unpleasant on my monitor at work! I thought I had a solution which is to load the near final image into PhotoPlus x6 and tweak the colour balance until the histograms for each colour channel line up well. I just could not get that to work for this image... or thought I couldn't. Maybe it's just lack of sleep!

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x6gas

x6gas

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I ran this through the SNCR routine in PI and thought it looked very much improved - I'll post it if you like so you can see?

That would be great Sara - thank you.

I tried strong and medium applications of HLVG last night - the medium looked good to my eyes...

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x6gas

x6gas

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By the way, I'm considering running a "processing challenge" with this data - especially if I manage to get some longer OIII. I think the data is pretty good - it's the skills of the processing that's the limiting factor :tongue:

Anyone up for that?

Ian

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johnrt

johnrt

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Great detail in the bubble there, excellent. I agree with Sara though on colour - too green and as she says a dose of SCNR transforms the image. If you're still working on this I can't wait to see the final version, it's superb already!!

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Coco

Coco

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I wasnt going to comment but as its been mentioned it has been tweaked beautifully by Sara..

As for the image its wonderful! very nicely detailed , one of the best ive seen in a long time.. ;)

1,960mm cannot easy I bet!! :eek:

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x6gas

x6gas

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I wasnt going to comment but as its been mentioned it has been tweaked beautifully by Sara..

As for the image its wonderful! very nicely detailed , one of the best ive seen in a long time.. ;)

1,960mm cannot easy I bet!! :eek:

Thanks Guy. It is a bit of a challenge at 1960mm f/l I must admit! I have done DSOs at the native 2800mm f/l and that really is hair-raising. I've got it working OK now, more or less. PHD was reporting an RMS of about 0.6 to 0.75 pixels on this - and the pixels of the guidecam are 5.6 microns (2x2 the effective pixels on the imaging cam are 7.38 microns) so just on the limit of pixel guiding - but that's probably irrellevant as I'm well oversampled at about 0.8" per pixel anyway. The guide graphs are quite alarmingly choppy to be honest, but it seems to work out OK. As I said earlier I think the data is pretty good - it's the processing that's the problem!

I must admit, though, soon as I've bagged the data for this (and I'm not quite finished just yet, especially if I go for RGB too) I am really looking forward to strapping on the Tak and to that lovely 450mm focal length!

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x6gas

x6gas

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I just put this through SCNR in PI at a 50% level. You could further tweak the colours if you wanted more out of them. Personally I like the blue that the PI SCNR routine leaves behind.

post-5681-0-81023300-1373548326_thumb.pn

Great detail in the bubble there, excellent. I agree with Sara though on colour - too green and as she says a dose of SCNR transforms the image. If you're still working on this I can't wait to see the final version, it's superb already!!

Thanks both.

So this is my tweak with an application of HLVG set to medium.

Actually I am cheating here as this is a much less aggressive stretch of the background with a heavier stretch of the Bubble blended back in...

post-11821-0-88192500-1373575506_thumb.p

I'm trying to be sure not to clip the black point, but I've moved it in a bit here since the background looks too light to me when I uploaded it:

post-11821-0-28162000-1373575917_thumb.p

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