ngc3621

[Shiraz]

Hi

had great fun with this beautiful object - really pleased to get anything at all on the faint outer arms. Digging around in the weeds meant that there is a lot of noise, but I think (hope) that some of it may be structure in the galaxy arms.

I am having a lot of trouble with colour balancing and would be grateful for any feedback.

thanks for looking. regards Ray

http://www.astrobin.com/full/162828/0/

[gregbradley]

A remarkable image Ray. I don't recall see any version of this galaxy before that has captured those outer arms so well. The galaxy though seems a tad unsaturated in colour. I would reduce the red/yellow in some of the brighter stars and look at ways to boost colour in the galaxy itself and try to get some blue into the spiral arms and a bit more red/yellow in the core.

Lab colour method is one way. There are others.

You really get a lot of detail in your images. They always surprise me.

Greg.

[alpal]

Hi Ray,
well done -
that's why I'm building a 10" f4 Newt.

cheers
Allan

[clive milne]

Colour balance looks fine to me Ray...

I would think it would benefit from more signal, but when is that ever not the case? and perhaps a whisker less de-con (personal taste)

nice shot

[Shiraz]

Thanks very much for the feedback Greg. I will reprocess in the next couple of days and repost. Those two bright orange stars are quite intrusive, but I am not the only one who has had trouble with them :) http://www.eso.org/public/images/potw1148a/

[gregbradley]

Looking at that ESO image your galaxy colour seems very similar. So perhaps its spot on.

Greg.

[RickS]

Very nice, Ray! Colours are good but conservative :)

[strongmanmike]

Great to see you back imaging galaxies Ray! :cool:

This has your usual level of good resolution going for sure (at least as good as I got with the AG12) aaand meah, yes the colour looks a little muted I suppose but many people will like it that way...my version done 12 months ago was considered a little too colourful by some, so horses for courses mate and yes pushed hard to reveal those faint outer arms and a little noisy as a result but I can still appreciate a good galaxy image in there, besides I would rather see the arms at the expense of noise.

Thanks for the view :thumbsup:

Mike

[Shiraz]

thanks Allan. A 250 Newt is a pretty good compromise scope if you can get it ironed out. Also, the RCC1 is an excellent CC that just fixes coma and has no other effect on the image. hope you get it sorted soon.


Thanks Clive. I was getting up into the tens of hours, so not much more to gain with more signal this season - what I really need is less sky signal. I agree that deconvolution could be slightly reduced - will try it. Unfortunately that is step 1 of a long process...


maybe, but I will try a bit more saturation and see what it looks like. I guess there is no "right" answer - these images are all a long way from anything that we could see, so it is almost as "free for all" as NB.


thanks Rick - appreciate the feedback


Hi Mike. remarkably similar images - you used more saturation, but that's about it. I could have used more noise reduction, but I find that process can sometimes turn everything plastic, so I generally prefer to leave a bit of noise. will post a more saturated image in the near future to see how that looks.

thanks very much for the feedback folks. regards Ray

[alpal]

Ray,
Hi Ray,
The 10" f4 is a magical size that can work on an EQ6 mount.
It's the biggest bang for the buck.
All is well - I am finding out a lot about mirrors etc:

http://www.iceinspace.com.au/forum/showthread.php?t=132458

Not only what I'll use - but many other manufacturers & also refractors.

cheers
Allan

[LewisM]

Ray, love it, agree it needs a LITTLE bootst in blue perhaps, but incredible detail - those background galaxies pop!

[alistairsam]

Looks awesome Ray, Even the ESO image doesn't show as much outer extensions if I'm seeing it right.
I'd go for a bit more contrast within the galaxy but each to their own..

Alistair

[Placidus]

Hi, Ray,

Looks superb to me. Stars beautiful. Faint outer spiral captured. Tiny fuzzies in the distance show good form.

I threw some hard statistics at the colour balance. Your histogram black point and dark regions look perfect. Ignoring monitor calibration, and just looking at the numbers, your core, and the ESO core, are both 10% saturated, theirs a perfect pink while yours shows the tiniest smidgin of magenta. Nothing in it. So far so good. The star-forming region at about 5 o'clock from the core in your shot is about 18% saturated cyan-blue, whereas theirs is 28% saturated cyan-blue. If we pretend the ESO shot is the "answer in the back of the book", there is room for you to increase the saturation of the mid-tones a bit. You'd need to mask in the galaxy, mask out the darks to avoid colour noise, and mask out the stars, as they are already pretty strongly saturated. Just doing that should give better blues in the star-forming regions, but might make the core a tiny bit too warm compared with ESO. Nice problem to have!

[SpaceNoob]

Very impressive, I love the little galaxy in the background too :)

[Shiraz]

yes, your references make interesting reading, particularly the testing of the refractors.


thanks very much Lewis. I will be attempting a mild repro soon to see what it looks like with a bit more oomph.


thanks for the feedback Alistair. It's always a balance between extracting the dim bits while not compressing the bright bits too much - will try out some more contrast in the core region.



thanks for the analysis and kind comments Mike. I will do a repro in the near future to see what is possible.


Thanks for the comments Chris - I also like that barred spiral and tried to keep it intact through the processing.

thanks all for the constructive input. regards Ray

[Leonardo70]

Great image Ray.

All the best,
Leo

[marc4darkskies]

Lovely image Ray! :thumbsup: Balance looks fine to me. I'd boost the colour a little bit though.

Cheers, Marcus

[Asterix2020]

Nice image Ray. I agree a little more saturation would be good, but I like colourful pics :).

[Paul Haese]

I like the detail in the inner arms, but think like some that the colour could be boosted a little. You might need to manage the bright orange stars when doing the boost though.

This is a good field of view and I think well composed when combined with the field of view it really works. I like the way the galaxy almost fills the field of view.

If it were me I would get some more hours of data. The background has a bit of a salt and pepper look which could be managed by some extra time. Just my opinion but I think getting more data is better than doing noise control.

A galaxy I have not seen much and something I should put on my imaging list.

[alpal]

Hi Paul,
It's in a great spot at about 1am - almost directly overhead.
The time is now - to image this one.
I hope others do too - it's a great target.

cheers
Allan

[NOMH]

Great capture Ray. I like the galaxy the way it is but some of the larger stars look a little funky. Great field of view and the background galaxy is a bonus.

JB

[Shiraz]

Thank you Leo.


thanks Marcus - am working on it


Thanks Paul. seems to be majorityagreement that it needs more colour


Thanks Paul. I intend to try for a lot more data, but getting the noise down will be hard on such dim features'


Yep Allan - it's right alongside the moon (or at least that's where it seem to spend much of its time).


Thanks John. Not sure what you mean by funky - if you mean the X shape diffraction pattern, that is due to the six mirror supports and is what this scope does.

regards Ray

[alpal]

No - according to Stellarium it's almost directly over head at 1am.

Actually 78 degrees at 1.15 am

[NOMH]

Hi Ray, not the spikes as my RC does that also. I was talking about the larger stars appear that the cores are really saturated, maybe over sharpened? The smaller stars look great.

JB

[multiweb]

A real nice close up Ray. Incredible details. :thumbsup:

[Shiraz]

thanks John - yep you are right, something went wrong with those stars - will redo to fix



thanks very much Marc.


Repro is progressing, but taking time. regards Ray

[tilbrook@rbe.ne]

Nice to your images again Ray!:)

Great detail as usual, if you don't mind me saying it could a little more saturation.
Don't know what the skies are like your way?
Plenty of clear nights here but the seeing is terrible.

Cheers,

Justin.

[madbadgalaxyman]

G'day, Ray,
I totally agree with Greg that the outer extensions of the very faint outer arms are better seen in your image than is usual, even on deep exposures.

Even so, the faint disk of this galaxy is known extend out even further than it does in your image......
a real challenge for astro-imagers

Some of the the outer spiral arms are bent well out of the plane of this galaxy; this bending from the principal plane of the galaxy (as defined by its bright inner disk) is most evident in the single prominent arm on the bottom right of your galaxy image, which gradually bends 90 degrees, but not in the same way that an arm would bend if it was in the same plane as the inner disk region.

Here is an image of the HI disk of this galaxy, taken with a radiotelescope, observing the 21 cm line that comes from neutral atomic hydrogen.
This "image" of the cold neutral atomic hydrogen gas in this galaxy actually represents, using greyscale,
the amount of atomic hydrogen gas in each line-of-sight::
179992
(from the THINGS survey, Walter et al., 2008)

As you can see, the Hydrogen disk, far from being planar, is very bent and warped! In fact, this is one of the weirdest gas distributions known in galaxies that appear mildly perturbed.

The departure of some of the outer arms from the plane occupied by the bright inner disk, is also very obvious in the UV image from GALEX.

cheers,
Robert

This is quite a fiendish galaxy, in its way. At first glance, it looks like just a standard pretty spiral, but the more you look at it, the more the distribution of arms and dust looks anomalous.

[Stevec35]

Nice work on this one Ray. I agree with others that the colour could perhaps be boosted a bit but not too much as I think you are pretty close.

Cheers

Steve

[Shiraz]

Hi Justin. I don't mind you saying that at all - in fact, thanks for the feedback.
the seeing for this one was about 2.6 arcsec on average, which is not great. Have recently had some better stuff though, but of course only while the moon was up.


thanks for the info Robert. I pushed the luminance as far as it would go (attached) and can see some of the additional extent and twisted shape, but my site is not really dark enough to get down deep.


thanks very much Steve. I am finding it hard to get much colour while still digging out the dim outer arms - I don't want to mess too much with the data, but it looks like treating the core and outer regions separately may be the only option.

regards ray

[Shiraz]

thanks very much to everyone for advice. I added more data, tidied up the noise, increased the saturation, tidied up the messy stars a bit, reduced the deconvolution and reduced the scale to hide the nasties that accompany more colour and to improve the apparent sharpness.
http://www.astrobin.com/full/169375/0/
appreciate the feedback to date
regards ray

[madbadgalaxyman]

Good stuff, Ray, this is just the sort of ultra-faint material that I love to see!

As mentioned in my other recent N3621 post, there is a commonly used name for very-very extended Extremely Faint Disks which are much more prominently seen in the ultraviolet regime :
"XUV" disks
(short for extended ultraviolet)

cheers,Robert

Just to confuse the issue, some galaxies with outer extremely faint and extremely extended Outer disks, are also known in the professional literature as Low Surface Brightness Galaxies !!
(e.g. NGC 289)