Well it’s been a while between new posts in the DS forum. OS work commitments and other tasks have consumed much of my time so haven’t been as active in the imaging scene as I’d like. Still keeping tabs on the imaging work submitted by others which acts as a catalyst for getting out there and collecting photons.
Anyway, without further ado, I’m pleased to present NGC 253, dubbed “The Silver Coin Galaxy”.
The barred spiral galaxy NGC 253 is the brightest member of the Sculptor group of galaxies. The group is estimated as being nearest to the Local Group of galaxies which includes our Milky Way galaxy. NGC 253 is one of the dustiest galaxies known. Dark dust patches conceal much of its spiral structure, also masking the HII regions. The galaxy appears elongated as we see it from an edge-on perspective. In spite of the dust, two spiral arms are subtly visible towards the edge of the galaxy with numerous bluish clusters of young stars. NGC 253 is approximately 10 million light-years distant.
About the image;
This is an LRGB composite consisting of 5.5 hours of data (L:120min; R:70min;G:70min;B:70min) taken over a few nights to beat the rising moon light contaminating the chrominance data (RGB). This isn’t much data to work with for such a slow telescope (F/9) and a dim target such as NGC 253. I wrestled for hours chasing colours. I haven’t got a good handle on the Astrodon filters and the colour balance characteristics they produce. Even after manual normalisation of the individual RGB channels using pixel math, I still couldn’t get the right balance with a 1:1:1 ratio (as per filter specs.) so opted for a more suitable balance. Kept a natural feel. The exact problem occurred with the Helix nebula image. The RGB data used 10min subs binned 2x2 to give a good S/N ratio. The RGB data is actually quite good, but on reflection, I should have also taken some shorter 5min subs to bring the star colours back. 10min subs was ideal for the galaxy chrominance, but pushed the stars too far (thus lost their colour information). Overall, I feel I’ve captured the “essence” of the galaxy reasonably well with handful of background galaxies dotting the scene. NGC 253 is quite high late in the evening this time of the season so lends itself well to getting good resolution as it crosses the meridian – darn those GEM flips!
Image processing;
All subs calibrated/reduced (dark, bias, flat), registered and Sigma-Reject combined in MaximDL. Luminance deconvolution performed in CCDSharp – two iterations. Colour combined chrominance (RGB) in MaximDL to achieve corrective colour balance ratios. Luminance initially stretched in MaximDL using DDP – no sharpening filters applied. Both images loaded into PS for further processing. Chrominance image stretched using shadow/highlights tool. Both images (luminance and chrominance) had gradients, but nothing considerably hard to deal with - created basic subtraction masks to remove these. Then moved on to cleaning both luminance and chrominance layers with the self-healing brush – removed colour inconsistencies and minor dead pixels that were not clean up in the combine function. Applied two selective layer masks, one to reduce noise in the dim areas and the other to highlight features of interest. Actually, I was rather slack with the noise reduction. Could have been a pushed the settings hard to better correct some colour noise.
I will try to make sure there is not such a long delay between posts. Though, I’m happy to produce a few quality images a year, than pump out a crap one every fortnight!
I hear the FSQ calling - back to wide fields is in order.
Well, that’s my couple of cents worth <pun intended>, thanks for looking and hope you enjoy it.
That is one of the best images I have seen of NGC253. In fact, I cannot recollect ever seeing the dust lanes so well defined, with so little noise, especially around the fainter edges of the arms.
A stunning portrait of one of my favourite galaxies – a fantastic effort in acquiring, processing and presenting this cosmic masterpiece. I am inspired and now have something to set my sights on.
That is one of the best images I have seen of NGC253. In fact, I cannot recollect ever seeing the dust lanes so well defined, with so little noise, especially around the fainter edges of the arms.
A stunning portrait of one of my favourite galaxies – a fantastic effort in acquiring, processing and presenting this cosmic masterpiece. I am inspired and now have something to set my sights on.
Cheers
Dennis
Thanks Dennis. Pleased you liked it. It is certainly a real gem to image, but rather difficult to get the spiral structure right. Thanks again.
Quote:
Originally Posted by EzyStyles
jase, so crisp and detailed! very very nice could even see some of the nebs around the dust lanes.
The core might be abit too bright.
Cheers Eric. Indeed, the core maybe a little on the bright side. If you stare directly at the core, your peripheral vision will notice the two barred spiral arms. My goal was to bring these out as I have not seen many images portray this effectively. I found a dim core lost this effect.
Quote:
Originally Posted by Rocket Boy
No wonder the $AU is up, look at the quality of this coin !!!
Well done Jase !!!
Thanks RB. Will not take credit for the AU economy though.
Quote:
Originally Posted by h0ughy
LOL more than a doller spent on this one - as the others said - well done
Cheers H0ughy. Appreciate the kind words.
Quote:
Originally Posted by leon
They may be few and far between Jase, but this is certainly worth waiting for, what a ripper of a shot.
Leon
Pleased you liked it Leon. Will try to step up my output. Will never compete against the volume of you DSLR guys put out. But then again, quality over quantity! Thanks again.
Last edited by jase; 03-10-2007 at 04:05 PM.
Reason: typos
Cheers Andrew. Appreciate the kind words. Hope you get up and imaging soon mate.
Quote:
Originally Posted by Blu Moon
sorry its taken me this long to post a comment but I was busy bowing in front of my LT!!! well done great effort.
Thanks Blu Moon.
Quote:
Originally Posted by EzyStyles
The core might be abit too bright.
As I listen to all critiques, I pondered on this further Eric. Having three iterations of this image in different forms, all have a similar core brightness levels. Attached is a "unprocessed" luminance. Unprocessed in that it has gone through registration, hot-pixel removal and sigma-reject then stretched using DDP to present the expected dynamic range. No other processing was performed. When looking at the final image posted and this image, the core has nominal values and as such I don't believe I've lost much (if any) data due to this (white clipping). I may reprocess a few more renditions, but for now I'm satisfied with the presented image. Thanks again.
Beautiful Jase!
I have had 2 looks at it so far today and its mind blowing!!
Makes me want to use it for my desktop so I can study it some more!
Absolutely well done!!
look forwards to your next post!!
cheers Gary
Beautiful Jase!
I have had 2 looks at it so far today and its mind blowing!!
Makes me want to use it for my desktop so I can study it some more!
Absolutely well done!!
look forwards to your next post!!
cheers Gary
Thanks for your comments Gary. Much appreciated.
Quote:
Originally Posted by jase
For the record and educational purposes... those having difficulties making out the spiral arms in the presented image - attached (below) is a NIR (near infra-red) image providing greater clarity than the visible wavelengths. (image courtesy of 2MASS)
Excellent Jase. The mark of a good NGC253 is how well defined the dust lanes are, I have found them difficult to resolve. You have certainly done them justice, and the colour balance is superb, also difficult to get right.
nice one Jase like all your shot stunning. Well done
Phil
Cheers Phil. Its pleasing when tasks come together. I had my doubts about the resolution of the luminance, but after a little deconvolution it worked out well. Thanks again.
Quote:
Originally Posted by iceman
Wow, how am I going to post mine now!?!? Brilliant!
Thanks Mike. Please post your rendition. Don't be deterred by my image. All images are special in their own right.
Quote:
Originally Posted by Bassnut
Excellent Jase. The mark of a good NGC253 is how well defined the dust lanes are, I have found them difficult to resolve. You have certainly done them justice, and the colour balance is superb, also difficult to get right.
most enjoyable
Cheers Fred. I focused on the dust lanes in the processing as I tried to emphasis the barred spiral structure. As can be seen comparing the NIR and visible wavelength images, its not easy to achieve (at visible wavelengths). The final colour balance I used was 1:0.7:1.3. This follows the characteristics/sensitivity of the KAI-11000M chip. Seems to have worked quite well. Thanks again.
Quote:
Originally Posted by plasmodium
Exactly what I was thinking Mike!
Jase - can you please post a list of what you intend to point your scope at over the next 12 months - I won't bother imaging them then!
Really good shot too......
Thanks Lee. Believe it or not, but I have completed my acquisition listing for the next three months. Sounds like a long time, but its only a handful of images as it takes time to deliver an image of good quality (especially with a mono camera and filters). I've worked out how the objects will be framed and in some cases a mosaic maybe required. Certainly not releasing the list - that would spoil the surprise.
Quote:
Originally Posted by Ric
A wonderful image Jase, so rich and detailed.
You have done a great job with this image.
Cheers
Cheers Ric. I'm pleased you enjoyed it.
Quote:
Originally Posted by Tamtarn
Another beautiful image Jase The full resolution is AMAZING
Thanks Barb and David. Appreciate the kind words.
Quote:
Originally Posted by DavidU
Awesome ! great detail......
David, thanks for your comments.
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Once again, thank you all for taking the time to look at this posting and make comment. Appreciate it.
, thanks for looking and hope you enjoy it.
jase, so crisp and detailed! very very nice could even see some of the nebs around the dust lanes. 
sorry its taken me this long to post a comment but I was busy bowing in front of my LT!!! well done great effort.
I focused on the dust lanes in the processing as I tried to emphasis the barred spiral structure. As can be seen comparing the NIR and visible wavelength images, its not easy to achieve (at visible wavelengths). The final colour balance I used was 1:0.7:1.3. This follows the characteristics/sensitivity of the KAI-11000M chip. Seems to have worked quite well. Thanks again.
