Lambda Centauri Mosaic 65 hrs - Revised

[Placidus]

A dream is to do a complete mosaic of the Scuttling Chook. Here we have a five panel region spanning just over 1 degree, with a total of 65 hrs of exposure.

H-alpha 20 hrs, OIII 24 hrs, SII 21 hrs, all in 1 hr subs. Aspen CG16M on 20" PlaneWave. Except for embedding an sRGB profile, all processing using GoodLook 64. We've reduced the original 7657 pixel wide image to 4096 pixels, for ease of handling.

[link to original full sized image deleted. New link to revised version below]


The range of textures in the region is quite amazing. A grand overview would be that we are looking at a hollow cloud of gas with a convoluted oyster-shell surround, strong in H-alpha (green) and SII (red), the space within glowing with OIII (blue). There is a strong impression that the OIII is blasting out toward the right, through the open face of the oyster.

The top of the oyster shell (12 o'clock) is adorned with the face of a bull, delicately outlined in thin shock fronts.

The left hand side, especially toward 8 o'clock, shows the rough, outer shell of the oyster, with bright crags and dark crannies.

Dead in the centre, we have the Running Chicken's famous Bok-Bok-Bok globules.

Worth a close look: About 30% of the way toward the top left corner is the Chook's nemesis, the evil Fox-Cat (whose face is a quantum superposition of vulpeculine and feline), quietly smoking a post-prandial cigar. For those who have trouble, the head is on the left, the curled-up contented body on the right, and the cigar is poking out toward the left of the mouth. This evil but well-fed creature explains the lack of a visible chook in this image.



Update:

New version (https://photos.smugmug.com/Category/Star-Forming-Regions/i-hFRnK9v/0/O/Lambda%20Centauri%2065%20hrs%20revi sed.jpg) with careful attention to red rings around stars, and slightly more contrasty.

[lazjen]

Very nice image! :thumbsup:

Q: Did you try to remove the star halos - the red/magenta? Or is this something you prefer not to do?

[Andy01]

Ah yes, "The Cauldron" as I like to think of it- as it resembles the olympic flame.
Crikey that's sharp- guess you can't argue with a 20" light bucket!
Great work guys, so does your software do mosaics too, I'm intrigued?

A very nicely baked chook, yum :)

[Placidus]

Thanks, Chris.

You should have seen the magenta stars before! We automatically identified well over 65,000 stars, and greatly attenuated their magenta haloes. However, we try not to mess too much with the haloes of the very largest ones, like Lambda Centauri. Perhaps we could have been more zealous here, but we think it's not too distracting. To get rid of yet more magenta, all we'd need to do is make the boxes around the stars a bit bigger.



Thanks muchly, Andy! Yes, the "Prometheus" module of GoodLook, which does registration, stacking, and artifact rejection, treats all images as highly overlapping mosaics. If it really is a mosaic, you don't have to do anything different or special. So long as all frames overlap the key frame by at least say 25%, all the registration, normalization, and blending happens automatically. Some of the subs were taken under full moon, others at new. The difference is handled automatically without having to do anything special.

[lazjen]

Thanks for the explanation. So removing the magenta is done when the frames are combined? What about trying to reduce the star sizes on the appropriate channels before combining?

It's certainly not too distracting as it is - there's a lot of features to look at.

[Atmos]

Absolutely love it MnT. From the 3D Bok Globules to the yellow fish being electrocuted (also yellow) towards the upper left.

[Bassnut]

Gee thats very good Mike. You see lots of pics of the middle bit, but this large mosiac with the walls of outer nebula is far more interesting, with fantastic detail in those walls, especially the middle left and bottom right. Far more going on there than the just the boks in the middle. Excellent composition too.

[Placidus]

The magenta halo removal is done at a fairly late stage. The first steps are uncontroversial:

- Register
- Winsorize the stack to remove outliers (cosmic rays, satellites, hot pixels, etc)
- Combine to produce an RGB image.
- Crop off margins with insufficient data.
- Set zero point.
- Colour balance to make image on the whole colour neutral.
- Say 5-10 rounds of Richardson-Lucy deconvolution, with anti-panda protection.
- Preliminary nonlinear (arcsinh) stretch, to produce close to final image.

Only now do we mess around with haloes:

- Find the stars, by comparing with a template. In this image, we found well over 65,000 stars. There are usually quite a few close double stars missed by the automatic algorithm, which have to be found manually.
- In a copy, automatically remove the stars. To do this, GoodLook estimates what is "under" the stars (using 3rd order bipolynomial regression on a Winsorized sample) to produce a more-or-less starless image. We prefer to err on the side of leaving some distant halo rather than messing with genuine nebulosity, but the distance we go out into the halo is adjustable.
- Subtract "starless" from original, to produce "stars only".
- In the "stars only" image, discard the OIII and SII utterly, leaving only H-alpha, and remap it to white.

- Now we do wavelet sharpening on the "starless" image. This is a good time, because you don't have to worry about black rings around the stars.
- Add the stars back in. We could of course just leave the stars out, and have a pretty good "starless" final image, but firstly there are always faint haloes left, especially on the very brightest stars, and secondly, stars are people too.
- Final tweaks in brightness and contrast.
- Yippee!

Apart from the deconvolution, and the complete discarding of the SII and OIII stars, there is no further attempt at shrinking the stars or rounding the stars. That seems unjustified, and perhaps the way to artifact and perdition.

Hope that makes more sense now.


Best,
Mike
(and Trish, who is trying to stop Honey West, the lorikeet, from typing too).

[Placidus]

Thanks, Colin! Tickled.



Cheers, Fred! We started with the middle, a year or so ago, but kept wondering what was just out of field. This image does have some sort of edge to it now.

[Maurice]

That's a stunning result.
Congratulations Mike & Trish.

[SimmoW]

Massive effort and beautiful image M&T. A great demo of your software too. Fun description.

Just loved scrolling around the big image, such crisp detail.

Just one minor point, the odd area has some hot or extremely saturated pixels, I'm sure you'll fix that. Unless you've discovered some new alien beacons or whatnot!

[RickS]

A wealth of detail and a lovely composition, M&T!

[Placidus]

Thanks, Simmo. Guilty as charged. No aliens. :D There are some peripheral regions with only two OIII subs contributing, and they are awash with blue hot pixels, cosmic ray hits, and even a satellite trail. So no outlier rejection in these regions. Another smaller patch has only two Ha subs. Just one more sub and they would go away. Will see what we can do.



Thanks, Rick. :)

[strongmanmike]

An excellent image guys, clearly a bit of work in that. Great colour palette, sharpening has been handled very well (you are getting under my radar more and more :P) and the contours and 3D features are coming through nicely. Winston Churchill's Cigar looks excellent and the stars look good - overall a rather dramatic portrait of this perennial favourite. I think the only minor buggy thing stopping this from being a complete show stopper is the red flaring/halos around a lot of the medium-fainter stars, even so it is really excellent anyway but love to see it again with the red reduced significantly.

Great work.....and even with the red, the amount of work, the programming and processing in that there image... makes it still worthy of one of these :prey2:....fix the red and you can have a whole row of em :lol:

Mike

[Placidus]

Thanks muchly, gentle teacher. Reckon you are right about the rings. We did go through the motions as mentioned to Lazjen, but obviously not well enough. Just a plain mistake. A great excuse to get a few more hours on the panel with insufficient OIII, make a strong espresso, and reprocess without changing anything else.

Expecting :rain::windy: :cloudy: next few days, including 50 mm rain. That will help the garden and wash the observatory dome.

[lazjen]

Excellent. Thanks for the detailed explanation. Gives me something to think about when I finally get back to processing an image with more than one channel... :)

[Ryderscope]

Stunning. Colour palette is great.
Plenty of detail to swirl around in.
Got lost looking at a myriad of shapes looking at me.

[Octane]

Simply outstanding, Mike and Trish!

I was really happy to see this pop up here as I'm also working on my own rendition of this subtle area of the sky. Gives me an idea as to what to look forward to. :)

I'm completely in awe of not just the 1 hour sub-exposures you guys do, but, also the fact it's processed in your own home-grown software. Very impressive!

H

[Camelopardalis]

What a beauty M&T, well done :thumbsup:

[Stevec35]

Great work as usual M&T! Lots of lovely crisp detail that you don't often see and the colour is just about perfect.

Cheers

Steve

[traveller]

Awesome image M&T. I spent quite a bit of time in the larger version of the photo and swam through the stars and gas fields.
Bo

[Placidus]

Thanks Rodney. Glad you like the colour. You're probably our closest IIS neighbour, so we expect you're about to see some impressive storms too. We've had 17 mm so far. Best close the observatory!



Thanks muchly, Humayun, for your encouraging words. Looking forward to seeing your interpretation.



Cheers, Dunk!



Thanks Steve. We're falling in love with the long focal length mosaic approach, even though it's very time consuming.



Hi, Bo. Delighted you like it. :)

Very best,
Mike and Trish

[alpal]

Hi Mike & Trish,
that's an excellent image.
I enjoyed voyaging around it.
I checked it out in Photoshop & it's easy to get rid of the red halos.

cheers
Allan

[cometcatcher]

Beautiful image M&T! I find the palette very ghostly, quite different to the usual chook, but very nice indeed.

[Placidus]

Thanks, Allan.

Our standard software can routinely get rid of the rings. We suspect we just set the radius of removal too low, and colourblind Mike didn't notice. :sadeyes: We're having another crack later today.



Thanks, Kevin. An interesting observation. Our palette is standard Hubble, RGB = SII Ha OIII, with the two constraints that the black point is set exactly to the foothill of the histogram for each channel (no cast or bias and no information loss), and the gains are set exactly so that each channel has the same average brightness (colour agnostic, as it has been called). That standard approach makes it easier to interpret, and easier to compare the "feel" of one object with another.

The one thing that we do vary is the contrast. Here, the challenge is how much emphasis to place on the faintest features. We like to keep away from exaggerating the faintest features until every image looks like a white piece of paper (the 'every cosmic microwave background photon is precious' theory), and instead try to bring out the structure of what one hopes is the main subject. But where to stop?

Very best,
Mike

[marc4darkskies]

Fantastic work M&T! :thumbsup: Just a gorgeous image that's nice to swim around in!

Hmmm - that's funny - I see a parrot head (Cockatoo)

[JA]

Congratulations on a wonderful image. It's very otherworldly :thumbsup:

Best
JA

[Placidus]

Thanks, Marcus. It's got the colours of a parrot!



Thanks, J.


We've reprocessed with careful attention to red rings round stars. Now it has grey rings around stars. Guess that is an improvement. But we've also made it a bit more contrasty.

New version here (https://photos.smugmug.com/Category/Star-Forming-Regions/i-hFRnK9v/0/O/Lambda%20Centauri%2065%20hrs%20revi sed.jpg)

[strongmanmike]

Yeeeah baby, now that's better

Ok...it's worth another :prey2:...Now to get the full row of'em...can you get just a little more intensity back into the star centres? they look just a tad washed out...THEN it will be prefect :thumbsup:....aaaaand you will have created one of the all time best versions of this area IMO.

Mike

[alpal]

Hi Mike & Trish,
I like the revision.
I've got to say - it was well worth the 65 hours -
it should be an APOD.

cheers
Allan

[Placidus]

Wow, thanks muchly Mike. So near and yet so far. :) Will look into the stars.



Thanks for the strong encouragement Allan.



There's a section along the left hand edge where we have insufficient data, and there are cosmic rays, hot pixels, and even a satellite trail. Must see if we can fix that with another night or two.

Sometimes it seems a shame to get rid of cosmic rays - they are after all amongst the most distant and violent things we ever get to capture. Pity they're just random and non-reproducible. Evidence of stuff going on, but we'll never know what.

[Atmos]

The stars in the previous version didn't bother me much, but as Mike says, they're a little... mushy?

The nebulosity pops more now though which is great!

[DJT]

Fantastic image MnT. Great contrast which brought out the details really well and the saturation really makes this a very punchy image.

I just finished processing a wide field of this but with nowhere near the hours and it tells. If you are at the imaging meet tonight it would be interesting to see how it comes out using Goodlook.

Well done guys.:thumbsup:

[Andy01]

Loving the revised version, :thumbsup:
At risk of adding salt to the above mentioned wound, if those were RGB stars, well then, wouldn't that be something ... :scared3:

[vlazg]

:bowdown::bowdown::bowdown:

That is brilliant M&T, well worth printing

[Phil Hart]

Impressive project Mike and Trish and a great result. The revised version is better but I'm with Mike about stars now needing some punch. I don't know how hard Andy's suggested RGB stars would be but if it's achievable the image is definitely worth it. You should be proud now though! :-)

Phil

[Placidus]

Yes, we can see that. Got an idea how it happened. See what we can do. Thanks for the helpful and constructive feedback.



Thanks, David. Eagerly awaiting your version.



Thanks Andy! RGB stars !!!! These are not the droids we are looking for ...



Thanks muchly for the encouragement George!



Hi, Phil. Great to hear from you, and thanks for the helpful feedback. Can think of a couple reasons why the stars might have come out a bit weak. Should be easy to fix.

Annoyingly clear sky out there at the moment, but with almost full moon and quite a gale.

Best,
Mike and Trish

[Paul Haese]

I like the second version best I think Mike. The depth is very good, kind of like looking through fog. The field of view is massive. Well done.

[Placidus]

Thanks very much, Paul.
The fog is a worry. Must clean the primary mirror. :)

[gregbradley]

That's a sensational image Mike. Plus what an amazing effort.
The processing is great and I like the restrained semi translucent look you have here.

One of your finest.

Greg.

[Placidus]

Thanks very muchly Greg. I like the 'restrained' description.

[rustigsmed]

wow great work M&T
this is one of my favourite areas of the skies.

its been fun comparing your amazing versions with my measly one of about 4hrs https://www.flickr.com/photos/80336656@N07/24924385306/in/dateposted-public/lightbox/
its a nice reminder that I need to get back out under the stars and add more data. weather and work has been holding me back - but the fine detail in yours is incredible a real showcase congrats :thumbsup:

Russ

[Stevec35]

Absolutely love it M&T! One of the best Hubble chickens I've ever seen. It's great as is but some RGB stars might be an interesting experiment.

Cheers

Steve

[Shiraz]

you nailed that - it's brilliant.

[Placidus]

Actually, your shot is virtually identical in all excepting the very faintest features. Modesty therefore forbids us to say how good it is.



Many thanks, Steve. Yes, starting to feel the need for RGB stars.



Thanks, Ray, we are much encouraged.

Best,
M & T

[RobF]

Just loved swimming around in this one so much. Thanks for sharing the fruits of all that labour with us!

Seems to have found its way onto my desktop however :question:
Hope that's ok!

[Placidus]

Thanks, Rob! Delighted that it's on your desktop.