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NGC6888 (Crescent nebula)

swag72

By swag72
in Imaging - Deep Sky

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swag72

swag72

Posted
Posted

This one has turned into a labour of 'hate' to be fair.  These things just never turn out as you expect...... I really do welcome all comments on this, good and bad. I dread to think how many hours this has taken in processing, tweaks here and there! I added the RGB as a way to give a more 3D feel instead of the flatter 2D that would come from just Ha and OIII.

Details:

M:Mesu
T: Orion Optics ODK10
C: QSI683 with Baader RGB filters, 3nm Ha and OIII 

50x1800s in Ha
51x1800ss in OIII
15x300s in each RGB

Totalling 54hrs 15 minsYou can see a larger version on my website here

Crescent_SGL.jpg

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Richard Hather

Richard Hather

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I agree with Matt no one will hate this I can't comment on processing or how you could improve the image.

But for me you've done yourself proud the nebular pops out almost 3D like which was your aim and the colours and detail achieve on the surrounding star field beautiful just doesn't do it justice, well done swag ?

Clear skies ✨????

Richard

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alan4908

alan4908

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Hi Sara

An excellent image. Very 3D like.  I like the starfield and the colour contrast of the Crescent with the background.  The Crescent details are also very impressive. 

How did you go about incorporating the RGB starfield into the narrowband image ?

Alan 

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ChrisLX200

ChrisLX200

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You certainly have the detail there but I agree something isn't quite right - then I realised my first impression is that it's the blue channel which is not showing up well. I don't know why - it is there but it's just not... blue (IYSWIM). Looking more closely the blue is also quite noisy in the fainter parts and the filametary structure is lost - which for 51x1800s is defintely not what I would expect. It must have been there originally so some step in the processing hammered it. Did you have a huge imbalance between the Ha and OIII? - the Ha being so bright it tended to overwhelm the OIII perhaps? I think I would try to get the NB levels closer (turn down the Ha brightness) and re-combine them. It's so difficult to say without the data in front of you and every one of these types of images is different so it is impossible to generalise, but my experience is that a wonderfully bright/contrasty Ha channel makes life hard when you come to add anything else to it!

(hope I'm not sounding too negative here... I don't mean to!)

ChrisH

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RuralBill

RuralBill

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I really don't see how anybody can find fault in the above image, including the OP, us mere amateurs look at that and think WOW, if only I could get anything like that I would be over the moon...c'mon OP it's superb, end of.......just accept its good, and enjoy the praise....otherwise us amateurs may aswell give up now... :)

Bill

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swag72

swag72

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Thanks guys for your comments. I'm glad that you like it..... but I don't :) There's too much wrong with it for over 50 hours of data.

@ChrisLX200 - Your comments are no more negative than what I feel about this image already..... I don't have the heart or stomach to try to reprocess it. The Ha was much brighter than the OIII - Even when I added another 6 hours of OIII to the data 2 nights ago, it made no difference to the overall brightness or noise of the OIII so I didn't bother using it.

I posted it so that people, if they felt inclined. could pick it apart..... I'm more than up for that :)

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Gina

Gina

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Posted

Sorry Sara but I think that's the best anyone could get.  There's more OIII in there than I've captured for that object and I thought mine was good!  I think you are just too self-critical.  That's it, that one is DONE, finished, no more to be done to it - leave it and move on.  There are so many objects out there to capture.  Just wish we had your clear skies here in the UK!

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Davey-T

Davey-T

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Posted

Ah the joys of astro' imaging, I think we tend to go colour blind after staring at the image for hours, processing as usual is very subjective and it's never "finished" asking other folks opinion may seem a good idea but a bit of a two edged sword.

Best just add it to the done pile and move on.

As usual a trawl of the internet turns up a myriad variety of Crescents of all hues.

How about a nice relaxing stress free mono HA image, that's usually all I can manage in the UK anyway :grin:

Dave

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ollypenrice

ollypenrice

Posted
Posted

I think it's very good. However, I, too, threw a lot of data into the Crescent (though not as much as Sara and not at the same FL) and I have always had a luke warm feeling about mine, too. I've never been able to put my finger on it. Chris might be onto it with the shortage of blue, but that isn't the imager's fault. Maybe it just ain't there!

Another thing is the strength of the background sky. To look 'right' the object needs to look stronger than the background. Because the background is a deeper, bolder red than the pinkish Crescent I think it has an aesthetic problem as a target - again not the imager's fault. Actually I think that's it. Imagine Sara's Cresecent against a plain dark sky. It would really have some bite. Pink foreground object against a bold red background? An artist probably wouldn't do it...

When I was working on mine I had the HaRGB as a bottom layer and the HaOIIIRGB as a top. Blinking the OIII on and off was amazing because the only thing it did was add/delete that outer shell of cling film. This was the most fun I had in the whole project and I thought that an animted GIFF of on-off with the shell would have made a more of the image than I felt it merited on its own.

Olly

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RobertI

RobertI

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You never know Sara, you might grow to love it one day! I rescued one of my dad's water colour paintings from the bin many years ago; he had thrown it away because he didn't think it was good enough. I put it in a nice frame and hung it on the wall, and now twenty years later it's one of his favourites! :) 

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Barry-Wilson

Barry-Wilson

Posted
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Hi Sara

I'm only able to look at your beautiful image on my mini iPad as I'm on holiday, not the best tool to view the colour balance and detail, however, the hi res image on your website is wonderfully detailed and striking.

It may well be that Olly and Chris have raised germaine points - muted blue channel in contrast the red-mapped Ha; and the aesthetically challenged red/pink contrasts.  However, these are present to varying degrees in Crescent images.  You have certainly achieved a 3-d effect.  Do you have a version with a darker sky to further lift the Crescent' from the background wash of Ha gas as Olly mused?

Your image is technically accomplished and it is fascinating to read (on this thread and others) that plenty of imagers have too been troubled in how to present this target (me included when I attempted this last year as a HOO).  I think this lends credibility to Olly's hypothesis regarding the non-complimentary colours the target offers.

For me the desire to achieve a truly accomplished image is what motivates me to keep trying.  Being a reflective practitioner as you are can only help. 

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swag72

swag72

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Thanks all for your constructive comments - I like the fact that Olly thinks it's not my fault :D  :D 

I didn't make the background any darker Barry as it is already at the edge of the histogram....... so I was in danger of clipping if I dug in any further. I have had a little tweak (Damn you folks of SGL!) and there's a VERY slight darkening of the background and a move away from the green.. also I redid the luminance and shoved that over the top..... so now it's got 62x1800s OIII instead of 51x1800s. I know that it's taken the outer shell out a little, but there's compromises to be had I guess. 

Now that's it.... no more tweaks. This target has badly got under my skin and I don't thank it for doing so. No higher res version of this one I'm afraid... it was done purely for you guys!

Crescent_SGL_1.jpg

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PatrickGilliland

PatrickGilliland

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Hi Sara

Think you are being to hash on yourself to be honest.  Glad you went with the additional RGB in my experience it is a requirement for this target.

I read the critique above and struggle to agree with it all from the perspective of what i like.  Personally i prefer V1, the image overall just feels better.  I note the comments on the blue but think you have actually nailed this give or take minor tweaks for taste.  It should be more teal than blue and your rendition creates a natural OIII envelope around the Ha which is how it should be.  The variation in the foreground and background is marked on this target and i think leaving the background with less detail/more NR works fine and actually helps create depth in the image.  Not seen above but again only thing i would change in V1 is a little work on the more colourful small stars fringes.  Just seem to have a little colour halo.  You could probably get away with a little more NR masked on the darkest areas just to reduce noise, yes it will be softer but again i think this will only work in your favor and the depth of field it will create.

The detail is excellent as per your normal images, RGB has worked with a great colour palate in my opinion.  We all strive for perfection of course but part of this hobby is never getting there but always improving.  That's not something to stress over but instead to be admired :).  Self-critique aside it is a great image and you know the next one will be better again.  Sounds like win, win!

Paddy

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