Thackeray's globules in colour

[Shiraz]

Hi

Finally got a bit of colour data to add to earlier Ha - Paul and I seem to be running in step with this subject.

HaRGB can suffer from colour defects near to bright stars and this image does. It is difficult to know how much saturation the nebula colour should have, but this is my best interpretation of the underlying physics of emission from low pressure gas - appreciate any feedback.
thanks for looking. regards Ray

scaled to page (this scale looks tidier): http://www.astrobin.com/full/101534/C/
full scale: http://www.astrobin.com/full/101534/C/?real=&mod=

Ha 5 hours at 5 min subs, RGB 1 hour each at 3 min subs.

Skywatcher 250f4 with RCC1
NEQ6
SX H694

[Paul Haese]

I like the reds, pinks and magenta in this image. The blue stars are always a problem in processing Ha when it is used as the lum in my experience. I found combining it with Lum does make a huge difference to this particular problem. I have just done a reprocess myself so you might want to consider tinkering a bit yourself. Although overall I like the image. I really like the field of view you present here.

[Rod771]

I think you've got the saturation spot on. It's not overly pushed and the colours are nicely balanced.

Looking good Ray! :thumbsup:

[Octane]

That looks absolutely beautiful!

Did you drizzle this set, too, Ray?

H

[David Fitz-Henr]

Yes, the colour processing looks stunning Ray, and you've brought out some nice contrast within the globules :thumbsup: As mentioned, the blue halos are hard to eliminate with HaRGB; but for some reason these halos appear off-centre from the stars in here?

[Shiraz]

Thanks Paul - will retry the processing.


Thanks Rod - appreciate the feedback


Thanks H. No, tried drizzle, but have not yet been successful - stars are not round and I am not sure why yet.


Thanks David. Oops, something went wrong with the registration - will go back and sort it out - thanks for picking that, I hadn't noticed it.

Regards Ray

[RickS]

Very nice, Ray!

[Bassnut]

Well, the dynamic range seems a bit compressed, although noise is low and detail is good. If your using Ha as Lum , I would have expected a bit higher contrast, the bunch of feathers part is a bit buried and bland. 5 min subs seems short for the Ha.

[Shiraz]

thanks Rick.


Thanks for the feedback Fred. I was surprised at how bland this region is in Ha - just lots of red stuff. However, it does have some interesting features - do you prefer something like this? http://www.astrobin.com/full/101597/0/

Ideal subs would have been 20 minutes, but I chose to use shorter subs in the good seeing - better resolution that way with an EQ6.

regards Ray

[Bassnut]

Yes I like that. On reflection the turbulence of nebula in the image is quite attractive. A pretty awesome effort on an EQ6 really, a difficulty rating of 11 at least.

[gregbradley]

Did you use some Ha as a luminance layer here? It can push the colour balance out.

Greg.

[Shiraz]

yep, it's straight HaRGB

[gregbradley]

How'd you blend in the Ha? Or did you do a Ha as luminance RGB combine?

Greg.

[Shiraz]

Ha as luminance RGB combine. Did a strong deconvolution and morphological erosion on the colour to minimise the star edge effects - not altogether successfully.

[gregbradley]

Ha as luminance may be fraught with difficulty. It'll wash out your colours and throw the colour balance off. If Ha as luminance usually creates salmon hues and washes out saturation. Ha and red combined in the red channel, Ha+ Luminance combined in some ratio for luminance is a common formula.Ha added to rgb would probably work best as Ha as red layer Ha as blue layer (delete the other channels on each layer) Ha as blue usually only 10%. Both these in lighten mode. Now it won't show unless the pixel is brighter than the underlying RGB image. You have control using curves.

Worth a try.

Greg.

[astronobob]

Amaizing stuff Ray, , , awesome field & top work :thumbsup:

[Shiraz]

Thanks for the advice Greg. I don't have any luminance - the seeing was only about 4 arcsec when I got the RGB, so there was not much point in trying for lum. However, I will try some other of the blends you suggest - as you say, worth a try. I am not sure why Ha does such damage when used as lum - after all, it only specifies how bright the image is, not what colour it is - must have something to do with imbalance in black levels and the effects of brightness on saturation (I guess)


Thanks Bob - appreciated.

regards ray

[multiweb]

That looks very good Ray. Not many RGB shots of the area with that much details. Nice. :thumbsup:

[Bassnut]

If you havent got Lum, just combine RGB you have for Lum, its the same thing.
I like Ha as lum for several reasons, but yes it can cause damage and is becoming less popular. If there is SII and OIII outside Ha regions, then those 2 will be suppressed with Ha as lum. If Ha is zero in a spot with SII or and OIII, those 2 will be invisible.

[gregbradley]

I agree Fred. Sometimes you can blend in a bit of Ha as luminance and it adds something. Not a lot say 10-15% opacity.
Best done probably as a hide all layer mask and selective add in for detail.

Greg.

[Shiraz]

Thanks for that advice. However, the RGB was taken with 4+ arcsec seeing, so any luminance that I can extract will be poorly resolved and not compatible with the <2 arcsec Ha. Will have to try again next year. Or maybe I should bite the bullet and really go to the dark side - and get an OIII filter.

regards ray

[Shiraz]

Thanks Marc. Regards Ray

[Astroman]

Nice one Ray, great looking colours and detail there.

[dvj]

I thought this was from one of the ASA telescopes until I read the technical card. Nice one!

[gvanhau]

Nice looking so far.

I'm also running on this subject, may be y post an advance of if this weekend.


Geert

[Shiraz]

Thanks very much Andrew

thank you John - appreciated. The Skywatcher has turned out to be a pretty good scope - with a very nice CF tube and tidy optics it can do quite well, even at 0.9 arcsec/pix, if the seeing is good.


thanks Geert - look forward to your image. - and congratulations on the football result.

regards Ray

[strongmanmike]

Hey even if the colour blending isn't quite on the mark, the Ha detail is excellent so I like the original Ha only version best :thumbsup:

Mike

[marco]

Very nice one Ray, I find the overall contrast a bit low, I tends to process a tad more contrasted but this is just a matter of personal taste and doesn't detach from your beautiful rendition
Clear skies
Marco