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x6gas

IC 443 / Sh2-248 the Jellyfish Nebula HaRGB

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I don't often get around to doing HaRGB imaging - mostly because it seems I hardly ever have the chance to shoot the RGB.  Anyway, in the few bits of clear sky we've had here I've been shooting the Jellyfish Nebula in Gemini.  This is probably the longest I've spent processing a single image; controlling Propus was not an easy task particularly as I was getting dirty great halos on all but the R sub-frames.  In fact, I've done so much processing that I am worried posting to the forum might bring out some artifacts that aren't apparent when I look in PS on my laptop...

This is 60 x 600s Ha, 42 x 60s R, 42 x 75s G, and 42 x 90s B, stacked in AstroArt 5, registered using RegiStar and processed in Photoshop CS5.

Scope: Takahashi FSQ85EDX

Mount: Celestron CGEM DX

Camera: Atik 490ex

Guiding: Atik OAG, IMG0H, PHD 2

post-11821-0-71605000-1394929809_thumb.p

Thanks for looking!

Ian

  • Like 5

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Ian that looks really good but maybe theres a bit of green in the background. Well done on the star control

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The star control looks good and the star colours overall look excellent. I think it's a little dark and could do with a little more of a stretch though? I like the colours that you've got as well. My HaRGB always ends up rather pink, you've got the lovely red that I always chase and fail to catch!

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Ian that looks really good but maybe theres a bit of green in the background. Well done on the star control

Yes I think you're spot on Daniel - a bit sleepy when I was working on this last night and should have gone the final yards.  There was a bit of gradient too and Xterminating that took care of most of the green, but I ran it through HLVG too, just for good measure!

Thanks for the comments!

The star control looks good and the star colours overall look excellent. I think it's a little dark and could do with a little more of a stretch though? I like the colours that you've got as well. My HaRGB always ends up rather pink, you've got the lovely red that I always chase and fail to catch!

Hi Sara.  Many thanks.  I've struggled with good star colour for most of my images (as you know, I usually do narrowband, but even when I've shot RGB stars I've been underwhealmed!  I've tried long subs and short subs and a mixture of both but this was achieved just by creating a star layer and taking the saturation to ridiculous levels.

You're spot on about the background so here's a version with more usual levels (though it looks a bit brown to me - maybe I've been looking at this for too long!)

post-11821-0-05583300-1394987971_thumb.p

And here's a version with an extra stretch...

post-11821-0-62345600-1394987939_thumb.p

That is a great image that you can be proud of - well done!

Thanks Richard - much appreciated!

Edited by x6gas

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Very nice Ian, dark & moody! Maybe just my preference, but perhaps it could be lightened just a tad, this may reveal further some of the nice detail within. I know exactly what you mean about star colours with LRGB, and I've also been trying to see how others bring this to the fore. Your star colours in this image are pretty good, although many of the blue-ish stars have a blue outer halo rather than the colour being uniformly across. Mine often have less colour, plus the halos, so if you manage to solve this I'm all ears!

Martin

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Very nice Ian, dark & moody! Maybe just my preference, but perhaps it could be lightened just a tad, this may reveal further some of the nice detail within. I know exactly what you mean about star colours with LRGB, and I've also been trying to see how others bring this to the fore. Your star colours in this image are pretty good, although many of the blue-ish stars have a blue outer halo rather than the colour being uniformly across. Mine often have less colour, plus the halos, so if you manage to solve this I'm all ears!

Martin

Thanks Martin.  I agree that it still does look a bit dark which is odd as this is using my 'usual' settings of 27/27/27 for the background sky on the most recent versions... unless it's been so long since I've done any imaging that I've completely misremembered what I usually do.... this is a distinct possibility!

So this version has a background of 40/40/40.  Too much?

post-11821-0-86351000-1394996875_thumb.p

I used a fairly simple routine for the star colour: Select the background using the magic wand, invert the selection to get only the stars, copy and paste as a new layer then increase the saturation by ~90%, blur a little and then set to blend mode color.  The trouble is the last bit as anything saturated below comes through as white so on overexposed stars the stellar core is colourless with any colour only in the halo.  I need to try again with even less streching applied to the stars, but this will be tricky as you still want the faint stars to come in.  I am guessing a careful stretch paying close attention to the top end is what's required...

Thanks again, Ian

Edited by x6gas
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Stunning picture

Thanks Robbo!

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I think you've cracked it with the last image Ian, processing looks spot on to me!

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I like the last one - Prefer the background and you've still maintained the nice star colour and nebula colour :smiley:

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I think that this is a superb image with excellent star control.  A long total exposure time, but clearly well worth every second. And I like the star and nebula colour very much.

Chris 

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The last one does it for me - super image.<br />

<br />

Dave<br />

<br />

<br />

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Thanks Martyn, Sara (again ;-)), Chris, Dave, Mark, Brenda, and twintin for the kind comments.

I really do appreciate the feedback and as has been shown again here it really does help me to improve my images.

Course I now see an artefact running along the bottom left of the images so it looks like my flats are over-correcting (don't think it's a stacking artefact as this is cropped) but I am getting there!

Thanks again everyone.  As usual +1 to the friendly folk at SGL!

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Very nice image!

Something you might want to try is LAB colour for the stars, thats worked quite well for me in the past. Then you can just copy/paste the star selection into the normal RGB version as a new layer (blend mode colour). LAB colour always seems to provide much better saturation.

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