Another distorted Southern Spiral Galaxy repro

[gregbradley]

NGC1808. Not often imaged but its quite a bright galaxy. Part of my ongoing Galaxy image series.

It has an odd shape - part spiral, part elliptical or are those tidal streams from an earlier interaction?

Thanks for the constructive criticism. I did a repro using the Lab colour channel technique from Louie and R Jay Gabany to bring out the colour.

CDK17, Trius 694, PME.
9 hours 20 minutes.

http://upload.pbase.com/gregbradley/image/154574611/large regular size

http://upload.pbase.com/gregbradley/image/154574611/original large size


Greg

[allan gould]

Very nice image Greg, we must have the same list but different weather. Damn these clouds.
Allan

[alpal]

Nice work Greg,
you got those galaxy arms very well.
I think I better delete my effort on flickr photos.

I had a bit of a play with your pic - I hope you don't mind?
This is a bit overdone & needs masking.
What about if you increased the colour using LAB mode like this:

cheers
Allan

[allan gould]

Great repro Allan - must look at LAB colour procedure. Do you have a link?
Allan

[alpal]

Thanks - one of Louie's many videos, see here:

http://www.youtube.com/watch?v=fE2GS_87Ct8

The idea is that you can adjust/boost the colours without changing the brightness.

[glenc]

That is an amazingly sharp and deep image Greg.
It is also great to see another image of a James Dunlop galaxy.
He found 50 southern galaxies in 1826 with the equivalent of a 6" reflector.
https://picasaweb.google.com/110048826379679252146/Dunlop28#

[RickS]

Great details and a really nice galaxy image, Greg! Colour a little muted for my taste too.

Cheers,
Rick.

[atalas]

Lovely galaxy with great detail Greg!well done dude.

[gregbradley]

Must be! There have been quite a few nice galaxies to target in the last few months. I am not sure there are as many coming up but I hope so.



Don't be silly Allan your image is great. You have to keep in mind the equipment being used. You would expect a deeper result from the CDK.

Gee I don't normally like repros but that does look nice. Star mask to protect the stars and some nice colour. Time for a repro already!

Not sure why the colour didn't come out in the first place. Is this R Jay Lab Colour technique?





Yes after seeing Allan's lab colour boost I agree. I thought it was just a plain coloured galaxy. There aren't many examples of it to compare.



Cheers Louie. Repro coming up though!

Greg

[gregbradley]

Thanks Glen. I have been putting more attention on sharpening and deconvolution in my galaxy images. Its another advantage of the small pixels of the 694 chip. Images take a lot more decon than with KAF8300 or KAF16803 images before showing artifacts. Same with sharpening. I guess that is the extra resolution from small pixels.

What got lost a little that shows up in the luminance is the "core" is really about 5 or 6 bright areas a bit like looking at the Trapezium stars in Orion Neb. I saw a similar core in another galaxy I imaged lately. Interesting. I seem to recall reading an article about some globs orbiting Sag A in the Milky Way close in. Its a fairly recent discovery. I wonder if these bright spots at the core at large globs circling the black hole?

Greg.

[RickS]

It's one that he mentions.

The technique is pretty well known, at least to people who dabble with LAB colour. It's the first technique introduced in the book I have been reading: "Photoshop LAB Color - the Canyon Conundrum and Other Adventures in the Most Powerful Colorspace" by Dan Margulis.

[nebulosity.]

Another awesome image Greg, looking forward to the repro :thumbsup:

Cheers
Jo

[gregbradley]

Thanks Jo Repro is now done, the same links in the original post.

Greg.

[alpal]

Good work - & I like the detail & colours that have popped out.

[gregbradley]

Thanks Allan and thanks for the tip.

Greg.

[SkyViking]

Nice image of yet another interesting galaxy! It seems to have a very prominent population of blue stars along the upper side. Thanks for the view :)

[Shiraz]

:thumbsup: that's a cracker of an image Greg - really nice in all respects.

[gregbradley]

Thanks Rolf. Yes it does seem to have the blue stars on one side. Perhaps a consequence of whatever caused the big loop.



Thanks Ray. Galaxy processing has its own workflow compared to other objects. Getting it together step by step.

Greg.

[marc4darkskies]

Nice work Greg! :thumbsup: An interesting galaxy. You've managed to pull out some great detail there!

Cheers, Marcus

[gregbradley]

Thanks Marcus. Multiple level decon helped get more detail.
Looking forward to your first light. The cloudy weather lately must have you chomping at the bit!

Greg.

[multiweb]

Terrific details. Some really cool colors and features in the spiral arms. Nice structure. :thumbsup:

[gregbradley]

I first started imaging this one at my dark site with the TEC and it had great structure even for the refractor. I didn't get to image it much down there so it became a target for the CDK.

Surprising it isn't imaged much as its quite bright really.

Greg.

[gregbradley]

Also for interest here is a crop extreme closeup of the galaxy revealing the interesting bright spots near the core:

http://upload.pbase.com/image/154599321

And here is the Hubble image of same:

http://commons.wikimedia.org/wiki/File:NGC_1808_HST_9788_06_ACS_06872 _01_wfpc_R658N_G_B814.png

This galaxy is well known to the scientific community as it turns out due to its massive star formation going on.

Greg.

[alpal]

It's a top image Greg,
I did a Google search & the only amateur image I can find that's better is this one:

http://www.starshadows.com/gallery/display.cfm?imgID=416

It has a bit more detail but still your image is right up there
as one of the best amateur images ever taken of this galaxy.
Still - you could maybe even extract more from your data
in the coming weeks or months with more time put into processing. e.g :
3 x drizzle stacking.
different stacking methods - entrophy weighted etc
finely adjusted masks to carefully select areas for LAB mode.

cheers
Allan

[gregbradley]

Thanks Allan.

Interesting Ha areas and the dust that appears to be rising up not far from the core not unlike our MW.

If I get some clear nights I'll take some Ha.

Greg.

[Bassnut]

Yours version is blown and ordinary Greg (albiet some nice detail), Allans repro is rediculosly brilliant. Why dont you process it that way?.

[alpal]

Thanks Fred,
this is a closeup -actual pixels -with a few more adjustments
to show how good Greg's data is.
Imagine what could be done with the raw data?

cheers
Allan

[gregbradley]

Its got some nice colour although a bit too colourful and noise is too intrusive. The stars are badly damaged. It would need another 8 hours to take such heavy processing.

Processing is often stretch versus noise and Allan's version is too far into the noise band and the data is stretched too much. Gives an artificial look.

Fred's into the narrowband where anything goes. This is a broad spectrum image and there is a natural look. I like saturated colours as long as they are natural. That colour is getting too much into the abstract and isn't my processing goal or style. I doubt those dust lanes are magenta, they would be brown. The Ha areas look good. Perhaps the same toned down a bit would be closer to my processing style. Each to their own there. The core has those interesting bright spots and they have come out more so that's good. I notice a few of my galaxy shots pick up these bright spots near the black hole. They are common not rare. I think a lot of the galaxies we have been imaging which show just a bright core have these bright areas surrounding the black hole. NGC2997 is one.

I took some Ha tonight during a brief period of clear skies. I may get some more and see what that adds. If the weather goes back to being clear it might pay to take some more exposure so it can take a bit more stretch.

Greg.

[alpal]

Hi Greg,
good luck with the extra data.
I look forward to seeing what you can do with the RAW data.

I was only using an 8 bit jpg for my example of what is there to be brought out.
I particularly like NASA's FITS Liberator to stretch the stacks from 32 bit FITS
& then save as 16 bit TIFFs for Photoshop.
I normally use the FITS Liberator X^1/5 function to compress the result as
of course the dynamic range is enormous.

I didn't like the green in my version so I increased the red & blue to overpower some of it which caused the false magenta look.
As for noise - I always leave some noise in a picture.
It looks more real than an overly smooth result.
If stars are damaged they can always be removed with fill & content aware in Photoshop
then replaced with copied & pasted versions from a preceding stretched version.
All this is a lot of work but I think 10 hours of data is worth 10 hours of processing time.


cheers
Allan

[allan gould]

Very interesting and revealing post. Followed this and gleaned a lot of information.
Allan

[gregbradley]

Thanks Allan. The extra 8 hours I was referring to was extra exposure time not processing time. Yes processing time can vary enormously. Usually the better data takes less time to process and the worse the data the more it takes to sort it out and get a decent image. My M83 image had something like 31 alternative variations before I was "happy".
Noise is one of those subjective elements in an image. A small amount is Ok but usually personally I prefer to have minimal. Different people object to or don't mind some noise. The real solution to noise apart from the usual processing tricks is more exposure time.

Stars are best protected with masks along the way if they are getting overly stretched. Especially with this camera as I find halation is an issue with this camera - perhaps more sensitive to IR than other cameras I have used.

Overall as a philisophy of approach I prefer to work on basics before processing. That comes from the observation that excellent data just falls out of the computer so to speak with little work and looks great and poor data heavily manipulated usually misses the mark. Best to have both going for you ideally.

Thanks for your processing alternatives though. Its good to have different viewpoints.

Greg.

[gregbradley]

I've gotten 2 hours of Ha and about an extra 2 hours of luminance and colour to add to it now.

Greg.

[Ross G]

Another great looking galaxy photo Greg.

All your galaxy photos look beautiful with nicely balanced colours and detail.

Stick with your techniques!

Ross.

[gregbradley]

Thanks Ross, nice of you to say.
I have about 4 hours of extra data to add to this one including 2 hours of Ha for the core and Ha areas.

I'll be adding to this one shortly. I think I'll take a bit more whilst its still in my imaging zone once the bad weather clears up.

Greg.

[LucasB]

Beautiful detail in this one Greg!
Lucas

[gregbradley]

Thanks Lucas. I was surprised at the amount of detail. I think because its quite a bright galaxy and also there was some good seeing at the time.

Greg.

[RobF]

Really enjoyed catching up on this one Greg. Beautiful image.
And Fred's comments have made my day nicely :rofl:

Its pleasing to see many of the Ice regulars with decent FL going out after so many extra galactic targets lately. This could be the start of a five year mission? :question:

[marco]

Beautiful Galaxy Greg and great resolution, I agree you managed it very well!
Regards
Marco

[gregbradley]

Thanks Rob. Yes I believe it could last 5 years. Even if only adding to the data each year making previous images deeper. The advantage of settling on a good system and then utilising it.



Thanks Marco. Much appreciated.

Greg.