NGC 247 Needle's Eye Galaxy & Burbidge's Chain in Cetus
After months of narrowband imaging in the back yard, it was nice to finally get some LRGB data under the beautiful Leyburn skies last weekend... and fill my CCD's wells with photons rather than dark noise for a change
I stumbled across NGC 247 (Needle's Eye Galaxy) while checking out the nearby NGC 253 in a star atlas, and thought it looked rather neat in ESO's image. The dark "needle's eye" seems like an uncommon feature of galaxies... maybe someone (Robert?) knows the story here? There's also a cute little line of galaxies very close by called Burbidge's Chain.
Even though it's listed as magnitude 9 in most catalogues, NGC 247 actually has a remarkably low surface brightness at magnitude 24. I decided to spend three full nights at 2x2 binning on it to make sure that I'd have enough data, and it worked out quite well for luminance.
There's plenty of room for improvement in the processing, but that'll have to wait until a rainy day in summer when uni exams are all over. Enjoy!
Hi Dave,
You certainly got an amazing amount of detail for a small scope.
It's hard to find a better picture unless with a large scope.
I probably would have taken some short exposures at 1x1 binning just for the bright stars
& copied & pasted them into the pic to reduce their sizes.
That's a lovely image, Dave, and was definitely worth all the integration time. The little galaxy chain is particularly cool. Look forward to your post exam repro!
Wow, what a pretty galaxy and in such a rich, stunning field. The pin-point detail in the arms and core is gorgeous.
Gulp – 32 hours total integration time, what a marathon effort!
Thanks Dennis! We had some spectacular seeing on a couple of the nights (sub-two second!) which definitely helped on the core detail.
The 32 hours isn't quite as impressive as it sounds... after the first night, I just have to uncover the scope, wait for cool down, start imaging, do the flip, and go to bed. Feels like cheating
Quote:
Originally Posted by Larryp
Lovely image, Dave!
Quote:
Originally Posted by alpal
Hi Dave,
You certainly got an amazing amount of detail for a small scope.
It's hard to find a better picture unless with a large scope.
I probably would have taken some short exposures at 1x1 binning just for the bright stars
& copied & pasted them into the pic to reduce their sizes.
cheers
Allan
Thanks Allan! The excellent seeing didn't hurt either A few of the stars are clipped in the raw subs, but I did also take shorter subs for later HDR combining. I think I need to learn a few more processing skills first to manage them better.
Quote:
Originally Posted by RickS
That's a lovely image, Dave, and was definitely worth all the integration time. The little galaxy chain is particularly cool. Look forward to your post exam repro!
Cheers Rick! Thanks for all your help & advice too... I think we could call some percentage of this your image too
Quote:
Originally Posted by gregbradley
The galaxy looks great and all those little background galaxies came up nicely.
Something has gone awry with stretching process and the stars - they look clipped.
When you end up doing the repro keep an eye on that early on to see what happened.
Greg.
Thanks Greg. The 3D plot of the stars look good (mostly non-clipped except for the brightest ones), but I wasn't able to deconvolve them to reduce bloat and compress their dynamic range (but it worked quite well on the small stars in the galaxy core). I'll have to learn a few more processing tricks over the summer. Any suggestions welcome!
Extreme imaging for sure Dave. Are you sure you were never into skateboards!
My first thought was that might have been the ESO image actually. Fanastic galaxy detail and the faint galaxies in the background a great. Might be worth doing some shorter exposures for the stars next time, but really, what a stunner!
I've got to get back to my M31. Having lots of gradient problems, probably because it started each night in the T'wba sky glow.
Very nice result Dave, that galaxy chain looks so cool and the colours in the galaxy look good with the HII regions showing nicely, I discarded this galaxy from my possible targets as boring so I'm glad you didn't I can't help but think there might be more in that mega data to surface though I would expect more myself anyway ...but then what would I know it's probably just a monitor thing
Hi Dave,
Do you know why the bright stars have a magenta and/or blue flare in the 5 o'clock position? Does your scope have field corrector installed?
The detail in the main object came out really well but I think the colour balance of the brighter stars is off, far too much orange. Perhaps due to trying to incorporate Ha, have you tried just RGB or LRGB to compare?
From a dark sky site the advantage of Ha on broad band sources (e.g. galaxies) is marginal, yes there are emission nebula in there but they are compact plus relatively bright, and the R filter can usually do a good job of isolating them. On galaxies with faint emission jets (M82 being the best example) the Ha can help out.
You mentioned binning 2x2, was that also the case in L? I think for the 8300 sensor it would be better to image L at 1x1 with subs long enough to overcome read noise. The CCD dynamic range is usually more compromised when binning due to the limited well depth of the read out register. I don't know what the hit is in 2x2 for an 8300, you could measure it by looking at the ADU count where a star flattop's.
Extreme imaging for sure Dave. Are you sure you were never into skateboards!
My first thought was that might have been the ESO image actually. Fanastic galaxy detail and the faint galaxies in the background a great. Might be worth doing some shorter exposures for the stars next time, but really, what a stunner!
I've got to get back to my M31. Having lots of gradient problems, probably because it started each night in the T'wba sky glow.
Thanks Rob! It was an all-round great weekend out there. I'm glad we had a day to catch up too.
Quote:
Originally Posted by strongmanmike
32hrs huh...? Did you have to rotate a dome?
Very nice result Dave, that galaxy chain looks so cool and the colours in the galaxy look good with the HII regions showing nicely, I discarded this galaxy from my possible targets as boring so I'm glad you didn't I can't help but think there might be more in that mega data to surface though I would expect more myself anyway ...but then what would I know it's probably just a monitor thing
Great job
Mike
No dome to rotate, but I had to huff and puff a lot to keep the clouds away I like hunting for the neglected ugly ducklings of the sky... I'm like the fishermen in the background of the John West commercials who pick up the ones that he rejects
Thanks Mike! The 10 hours of Ha don't really count, and 22 hours in my piddly 8 inch scope is like 10 hours on yours, and by the time we compare relative sensitivities of our respective chips, I've really only got about same signal-to-noise as one of your efforts
Yep, I agree that there's plenty of more to dig out of this one. I need to learn more processing skills, as I've primarily focused on good data capture this year. I suspect a lot of Sidionio-ing in my future
Quote:
Originally Posted by ericwbenson
Hi Dave,
Do you know why the bright stars have a magenta and/or blue flare in the 5 o'clock position? Does your scope have field corrector installed?
The detail in the main object came out really well but I think the colour balance of the brighter stars is off, far too much orange. Perhaps due to trying to incorporate Ha, have you tried just RGB or LRGB to compare?
From a dark sky site the advantage of Ha on broad band sources (e.g. galaxies) is marginal, yes there are emission nebula in there but they are compact plus relatively bright, and the R filter can usually do a good job of isolating them. On galaxies with faint emission jets (M82 being the best example) the Ha can help out.
You mentioned binning 2x2, was that also the case in L? I think for the 8300 sensor it would be better to image L at 1x1 with subs long enough to overcome read noise. The CCD dynamic range is usually more compromised when binning due to the limited well depth of the read out register. I don't know what the hit is in 2x2 for an 8300, you could measure it by looking at the ADU count where a star flattop's.
Best,
EB
Eric, thanks for your tips - very much appreciated The colour flaring is from a combination of factors. I took equal length subs for RGB, but the combine ratio using eXcalibrator was 0.76 : 0.78 : 1.00 and I think the R subs bloomed a bit more in camera. The saturation boost really messed it up.
Yes, I binned the L in 2x2 as well - but in retrospect that wasn't a good idea. It has an especially shallow horizontal shift register that causes weird blooming patterns, which probably didn't help with the colour combine.
The Ha data was actually from my back yard and not dark skies, which is fairly easy/cheap to gather as I have the scope set up semi-permanently there.
I usually aim for sky limited exposure lengths, but it's hard to judge without regularly shooting LRGB regularly. My blue channel was spot on Starizona's ideal exposure calculator at 2x2 binning and 30 mins each, but the red only needed a bit over 20 mins. I overshot the luminance by a fair bit (20 mins instead of an ideal 14) which might explain some of the star bloat too.
There's still a lot to learn... and the more I learn, the more I realise there's yet even more that I don't know
Quote:
Originally Posted by TimberLand
Very cool, great colours. I'm also a fan of galaxy groups and chains, you have got yourself a keeper there. Mag 24 impressive.
Love everything about this image. Colour and detail are great, those stars really add impact to the image.
Almost feels like you could float amongst them.
Great image,well done Dave! you deserve a great result from all that hard work gathering data 32 hrs! wow! congratulations.
Thanks Chris. It's the setting up, aligning, calibrating, target acquisition, processing, etc that takes a lot of time and effort... once the gear's set up and working 1 hour vs 32 hours isn't all that different
Quote:
Originally Posted by tilbrook@rbe.ne
Outstanding Dave!
Love everything about this image. Colour and detail are great, those stars really add impact to the image.
Almost feels like you could float amongst them.
Thanks Justin! So many pretty galaxies overhead at the moment - nice to be able to grab one.
I love the detail in the galaxies, but can't help feeling distracted by the surrounding stars, especially the orange ones. Maybe Rogelio's star reduction tool might help?
Crikey Dave, that's excellent. This is a very dim object and you have lots of fine detail in there. Suspect that the minor issues with stars will disappear when you get time to reprocess, but for me this image is about the galaxy anyway, not the stars. all the best with exams. regards Ray
Fantastic image Dave. Such an impressive galaxy and you've nailed it very well. Adore the background galaxies adding an extra dimension. Good to see an tradition true colour image in your portfolio as you make the most of the unpolluted Leyburn skies. Top work.
A few of the stars are clipped in the raw subs, but I did also take shorter subs for later HDR combining. I think I need to learn a few more processing skills first to manage them better.
so I'm glad you didn't 
I would expect more myself anyway ...but then what would I know it's probably just a monitor thing 
