Centaurus galaxy cluster in colour

[Placidus]

NGC 4603, NGC 4622, and at least 98 friends, finally in colour, after a battle.

Big image here. (https://photos.smugmug.com/Category/Astrophotography-at-Placidus/i-zXhRJtD/0/5671ba45/O/0142%20Centaurus%20Sextet%20NGC%204 603%20NGC%204622%20and%2098%20frien ds%20L%2018%20hrs%20RGB%207h30.jpg)

Lum 17.5 hours in 30 min subs, RGB 7.5 hours each channel in 30 min subs. Aspen CG16M on 20" PlaneWave on MI-750 fork. Field 36 min arc, 0.55 sec arc/pixel. Processing GoodLook 64, and a buttery Hedberg chardonnay.

What we especially like: the huge mix of different kinds of galaxy, ranging from what looks like a small blue dwarf irregular galaxy at 6 o'clock, through the several big, image-dominating face-on spirals, some very tightly wound, some more like a Superman "S", to the absolute host of extremely distant orange-red ellipticals. The whole story all there in front of us.

We've tried to bring out the (actually fairly subtle) colours in the various different kinds of galaxy without going too far over the top. A closely run thing, perhaps, but the biggest stars came out looking pretty.

The 17.5 hours of luminance gave us pretty good morphology on many of the small to medium-sized face-on and edge-on spirals in the far distance.

(Taking it was another story. Everything that could possibly go wrong did. Earth currents from a lightning strike just over the fence may have had something to do with it, but Sod's Corollary to Murphy's Law seems relevant. Dead computer. Replacement allegedly identical but needed new camera drivers for reasons unknown. Two power supplies failed, in different ways. A fan on one of the cameras failed. Roof position sensor touchy. Finally, fan on generator house exploded just as Trish started the generator. All working now, but for a while we were seriously considering gardening, sculpture, and knitting as hobbies.)

[alpal]

Nice work Mike & Trish,
you can see a similar shot with & without annotation here:
http://www.capella-observatory.com/ImageHTMLs/Galaxies/NGC4650etal.htm

cheers
Allan

[Camelopardalis]

That's stunning, good work M&T :thumbsup:

[Atmos]

Fantastic shot Mike & Trish! Hundreds of tiny background galaxies coming though!
Found a couple of things I couldn't quite figure out what they were.

[Placidus]

Hi, Allan,

Thanks for the Namibian link. Their stuff is routinely excellent. Ours is more narrow field, more zoomed in, and on this occasion we're showing more detail, which is extra thrilling for us, even if it is cheating. We'd love to do a mosaic, extending toward the East, to eventually cover the same field they did. There are some great galaxies in that direction.

Best,
MnT

[Placidus]

Thanks, Dunk!



Hi, Colin,

Artifacts of unknown origin. We focus once per frame, due to effects of heavy cameras, off-axis guider, and 10 position filter on the sadly inadequate (and already once replaced) focuser. A side effect is problems with ghosting after-images from bright stars in the focus shot. We don't want to flush the sensor between shots, because that measurably increases noise, and we're more interested in catching faint stuff than we are in getting rid of these blobs of ectoplasmic slime (don't cross the beams). If we did more colour subs, statistical outlier rejection should get on top of them.

Glad to see you're looking so closely! :D

Best,
M & T

[gregbradley]

A stunning image there. Love it. That spiral galaxy on the bottom right is amazing. Its very Milky Way in shape. Perhaps almost identical although I imagine our MW has a slightly more barred central core but those spiral arms especially the ones that have half spiral splitting off are very similar.

Beautifully round stars at 30 minute subs is superb tracking.

A mesmerising image. One of the best images for ages.

Greg.

[Atmos]

I got kinda lost in all those tincy wincy galaxies, hundreds and thousands of them! Gotta be difficult getting rid of every little reflection ect in those bigger systems :)

[marc4darkskies]

A wonderfully engrossing image there M&T! Beautiful! And what an effort! I wish my conditions here were compatible with such heavy duty integration times!

Cheers, Marcus

[Tony_]

Magnificent image - I love these galaxy cluster images. Far beyond my capabilities.
I searched out of interest - the galaxy at 6 o'clock is called LEDA 166139. type dE D

Tony.

[Placidus]

:) :) :)

Going from mono to colour seems to help, especially with the faint irregulars (gritty blue patches) and very distant ellipticals (nice salmon colour). In mono, they are just grey blobs. On the other hand, a blob that's just in say the red channel and keeps jumping about in different subs is either an artifact or an alien.



Thanks muchly Marcus. The weather has been evil. Wind 65 KPH the other night.



Thanks for that, Tony. Going to have to dig out my galaxy textbook and read up on what that might mean.

[codemonkey]

Epic works guys, "engrossing" as Marcus says. Got to be dedicated to spend that amount of time on one target. Thanks for sharing.

[Retrograde]

Superb work Mike & Trish.
Lots of fun noodling around the hi-res image scoping out distant galaxies and the detail in those face-on spirals is delicious.

[RickS]

Fantastic work, M&T! I just spent 10 minutes doing an annotated version of the luminance to identify PGC166139 only to find out that Colin had already named it :) It looks particularly stunning in colour. Great to see some detail in even tiny galaxies.

Cheers,
Rick.

[alpal]

Yes,
yours has more detail - you've beaten Namibian skies.
The left hand side has some nice galaxies in their picture so
a mosaic would be marvelous to do to capture them as well.

cheers
Allan

[Andy01]

Crikey, Ay Carumba, Jumping Jehosophat, Holy bazillion galaxies Batman!
That's a mighty impressive image guys :eyepop:
Amazing star colours too - No matter what you believe, that just goes to show how amazing the universe is!
:bowdown:

[strongmanmike]

Great shot guys :thumbsup: apart from the tight circular spiral, my favourite odd ball object is that coloured clump of seaweed right at the bottom in the middle..I assume it is an irregular galaxy of some type..?

Mike

[RickS]

It is PGC166139

[strongmanmike]

Ah cool :thumbsup:

[Slawomir]

A beautiful image M&T that captures the essence or the reason for us pursuing astrophotography.

[Placidus]

Thanks Lee. The Lum used 3 successful nights plus another 2 or 3 nights of character-building only, due to exploding equipment. We only did one night of colour. Perhaps in retrospect one more night of colour might have helped, but we'd had enough.



Hi, Pete! Glad you liked it too.



Thanks muchly, Rick.



That's very kind of you, Andy. We are much encouraged. It's amazing to think that one of those really bright stars is huge, even one of the galaxies has perhaps 200,000,000,000 of those, there are at least a hundred identifiable galaxies in the image, the image is a tiny fraction of the whole sky, and then perhaps it goes on forever.



Thanks, Mike. Can't find anything about that particular galaxy, but it sure looks somewhere in the same general class of beastie as an irregular or dwarf or both.



Thanks, Suavi. That's very kind.

MBJ: When I was tiny, I loved the How and Why type books that explained about the stars, their colours and spectra, how it all worked (and somehow at the same time it was ok enjoy the myths that went with the constellations). Now, at the end (as the Emperor would say) it's wonderful to be able to see some of what's in the thicker books.

Best,
M & T

[Stevec35]

Great stuff M&T. The Centaurus cluster is one of my favourites and to quote a contemporary politician you have captured it bigly.

Cheers

Steve

[cometcatcher]

Very lovely image M&T.

[edwardsdj]

Stunning image. One of the best I've seen in a while.

I've been lost in it for about an hour now!

[SimmoW]

Man, how symettrical is that 'main' galaxy??!! I'd call her the Supermodel Galaxy! Gorgeous deep work here M&T

[billdan]

Awesome M & T, I also spent a lot of time studying the image. Would make a great A1 poster for around the snooker table.

Bill

[Placidus]

Steve, Kevin, Doug, Simon, Bill,

Many thanks for your kind encouragement.

[markas]

M & T,

Wonderful result for all the time and effort. Great image!

Mark

[Paul Haese]

Nice image Mike and Trish. The hours you put into the colour are really showing here. Back ground is nice and smooth too. A really nice mix of galaxies captured and maybe even some IFN.

[Octane]

That's just staggering. :O :O :O

Awesome work, M&T. :)

H

[topheart]

Hubblesque!
Wow!

Cheers,
Tim

[Joshua Bunn]

That is Beautiful... nice framing and star colour and that's just to begin with. I've just turned my scope over to this cluster, this is so inspiring. How did you manage to keep the star colour in half hr colour exposures on a 20" scope?

Josh

[Placidus]

:)



Many thanks, Paul.

With galaxies we hope to get the colour at least approximately right and then exaggerate differences that tell us about what's going on. Occasionally wondered if exaggerating colour is somehow cheating, but perhaps no more so than using a telescope and long exposures to make it brighter!

Always hard to know when it's IFN and when it's dodgy flats. A big problem with our gear is the camera is very heavy and bolted on using four hard-to-get-at bolts. You can't rotate it. If we could rotate to several different positions during a session, we'd be more confident that we had true IFN. Sigh.



Thanks muchly Humayun. That's very encouraging.




Thanks Tim !



Many thanks, Josh. Good hunting with your scope!

How we preserve star colours:

The PlaneWave does tend to produce a rather fat, burned-out, sequin-like disc (due to bad seeing more than optics tracking or collimation), and as you rightly imply, there's nothing one can do about that white core.

But there is always an extended gently fading halo that does not burn out, and happily retains the colour of the individual star, no matter how long the exposure.

Processing matters. A mistake is to start with the image for example even very slightly too blue, and then to crank up the saturation. Now everything is blue. The true colours are irretrievably lost. Trying to balance the colour at this late stage will produce white stars. So we're very careful to get the zero point right, by careful inspection of the highly magnified foothill of the histogram, then balance the colour for the image as a whole (or sometimes just for one or more galaxies of special interest), and only then increase saturation. Being colourblind actually helps here - Mike's not tempted to try doing it by eye, where a wrong white point can hide a wrong black point. It's all done using actual statistics.

Very best,

[Shiraz]

keep coming back to this one for another look. what a beautiful image.

The galaxies are clearly the primary attractions, but also really like the star colours - definitely worth the long RGB exposure times.

[Placidus]

Thanks muchly, Ray.