The extended halo of NGC 253

[strongmanmike (Michael)]

Well being a blueaphile I'm gunna say it is way too red/magenta and I recon there needs to be more brightness variation from centre to edge of the galaxy buuuut otherwise....man, a pretty damn cool image that Ricki With plenty of exposure you have certainly revealed the faint outer halo and display it quite nicely too. Yes, a real shame you weren't able to reveal the S-Bend guess it takes incredible stretching skills to be able to show that, oh well, next year mate . The limiting magnitude looks to be pretty faint too.

Very well done

Mike

[Bassnut (Fred)]

Gee, spectacular 3d detail there Rick, top work. Who cares about the stars . The diffraction spikes add drama.

[gregbradley]

Originally Posted by strongmanmike

Well being a blueaphile I'm gunna say it is way too red/magenta and I recon there needs to be more brightness variation from centre to edge of the galaxy buuuut otherwise....man, a pretty damn cool image that Ricki With plenty of exposure you have certainly revealed the faint outer halo and display it quite nicely too. Yes, a real shame you weren't able to reveal the S-Bend guess it takes incredible stretching skills to be able to show that, oh well, next year mate . The limiting magnitude looks to be pretty faint too.

Very well done

Mike

I don't know if Rick is willing but it would be cool if he uploaded his ata to Dropbox and invited others to have a go at processing. It could be a fast track way of gaining some processing info if those who process it post what they did.

This is potentially the most interesting data I have seen for a while.

Greg.

[RickS (Rick)]

Originally Posted by multiweb

Beaute shot Rick. Sharp as and not over processed like many I've seen before. Great details.

Thanks, Marc!

Originally Posted by John Hothersall

That image jumped out at me so rich and bright, I thought you had used Ha as a few red patches have come out. Only criticism is the bright stars and diff spikes are a bit too dominant but you have brought out the halo very clearly.

John.

Thanks, John. Good points. The stars did blow out when I stretched the halo despite some attempts to control this. I need to work on my mask generation.

Originally Posted by peter_4059

Nice going Rick. Heaps of detail and sure is high impact. Agree with what others have already said re the red stars. They seem to have a dark ring on my monitor.

Thanks, Peter. That's another thing I will try to correct.

Originally Posted by strongmanmike

Well being a blueaphile I'm gunna say it is way too red/magenta and I recon there needs to be more brightness variation from centre to edge of the galaxy buuuut otherwise....man, a pretty damn cool image that Ricki With plenty of exposure you have certainly revealed the faint outer halo and display it quite nicely too. Yes, a real shame you weren't able to reveal the S-Bend guess it takes incredible stretching skills to be able to show that, oh well, next year mate . The limiting magnitude looks to be pretty faint too.

Very well done

Mike

Thanks, Mike. I did deliberately pick that colouring based on an eXcalibrator colour calibration and a bit of a survey of NGC 253 images that I liked and didn't like, but perhaps I'm a magentaphile I did flatten the dynamic range of the galaxy a bit to bring out the halo and I agree I could probably do better with some more work. I also promise to do better on the S-bend next year

Originally Posted by Bassnut

Gee, spectacular 3d detail there Rick, top work. Who cares about the stars . The diffraction spikes add drama.

Thanks, Fred!

Originally Posted by gregbradley

I don't know if Rick is willing but it would be cool if he uploaded his ata to Dropbox and invited others to have a go at processing. It could be a fast track way of gaining some processing info if those who process it post what they did.

This is potentially the most interesting data I have seen for a while.

Greg.

Greg: I don't think I'd want to make a public release but I'd be happy to make the data available on request.

Cheers,
Rick.

[allan gould]

Rick
Another superb image. Just love how well you have brought out all the faint halo.
Allan

[RickS (Rick)]

Thanks, Allan! I've had some great feedback for a repro but I think it only needs a bit of tweaking. It might be a bit OTT for some people, of course

[astronobob (Bob)]

Wow, EyePoPPin image Ric, Dig that Lots

[Shiraz (Ray)]

Excellent image Rick - got a lot of really dim stuff and at very high resolution. Top stuff.

FWIW, I think it looks just like a deep image of 253 should look - the dust lanes have a fair bit of red even in much shorter exposures and as you go deeper, they should look redder. I would not have used quite as much saturation, but that is just my personal taste and not anything to do with your fine image.

Regards Ray

[broca (Steve Coates)]

Fantastic work! The time you put into this has paid off well!

[RickS (Rick)]

Originally Posted by astronobob

Wow, EyePoPPin image Ric, Dig that Lots

Thanks, Bob!

Originally Posted by Shiraz

Excellent image Rick - got a lot of really dim stuff and at very high resolution. Top stuff.

FWIW, I think it looks just like a deep image of 253 should look - the dust lanes have a fair bit of red even in much shorter exposures and as you go deeper, they should look redder. I would not have used quite as much saturation, but that is just my personal taste and not anything to do with your fine image.

Regards Ray

Thanks, Ray. I may tone it down just a little when I address some of the other issues. Part of the problem is my fantastic calibrated 27" NEC monitor. It makes everything look great!

Originally Posted by broca

Fantastic work! The time you put into this has paid off well!

Thanks, Steve.

[marco (Marco Lorenzi)]

congrats on the attempt Rick, the halo is well visible. I too find the overall look a bit reddish but that doesn't take much out of the "impact" of the image

Regards
Marco

[Tandum (Robin)]

Yes, definitely an original colour scheme. Never seen anything like it before.

[jase (Jason)]

Great work in picking out the extended halo, Rick. Sure is an incredible sight to see. Equally impressive are the details you've obtained throughout the dust lanes. I don't mind the colour presented. The HII regions really pop so you've on to something. Well done.

[RickS (Rick)]

Originally Posted by marco

congrats on the attempt Rick, the halo is well visible. I too find the overall look a bit reddish but that doesn't take much out of the "impact" of the image

Regards
Marco

Thanks, Marco.

Originally Posted by Tandum

Yes, definitely an original colour scheme. Never seen anything like it before.

Is that good or bad, Robin?

Originally Posted by jase

Great work in picking out the extended halo, Rick. Sure is an incredible sight to see. Equally impressive are the details you've obtained throughout the dust lanes. I don't mind the colour presented. The HII regions really pop so you've on to something. Well done.

Thanks, Jase...

[White Rabbit]

Lovely shot Rick.

Would you mind explaining how you came about your image plan ie the number of subs and length of subs for each channel? I understand it's a pain but would help us newbs out here in wilderness lol.

Your image plan was 7x900s R, 7x900s G, 7x900s B, 30x600s Lum would mind if I ask why the lum channel is only at 600s but 30 subs? I understand that 30 subs would make it a smoother image than 7 but I dont understand why the colour channels are a full 1/3 the length longer than the lum?

Cheers.
Sandy

[RickS (Rick)]

Originally Posted by White Rabbit

Lovely shot Rick.

Would you mind explaining how you came about your image plan ie the number of subs and length of subs for each channel? I understand it's a pain but would help us newbs out here in wilderness lol.

Your image plan was 7x900s R, 7x900s G, 7x900s B, 30x600s Lum would mind if I ask why the lum channel is only at 600s but 30 subs? I understand that 30 subs would make it a smoother image than 7 but I dont understand why the colour channels are a full 1/3 the length longer than the lum?

Cheers.
Sandy

Thanks, Sandy.

The image plan is a bit of a wet finger thing. I could be more scientific about it and probably should be, but I have a reasonable idea of what works for my scope/camera combination.

Some of the factors governing my choice of exposure time are:
- imaging at a fairly slow f/9 -> long exposures to collect significant data
- sensor has a reasonable amount of read noise (8 e-) -> long exposures to overcome read noise
- a sensor with deep wells -> long exposures won't tend to saturate stars too quickly
- dark skies mean less sky glow and associated noise -> long exposures
- Luminance collects data much faster than RGB (the colour filters block approx 2/3 of the incident photons) so shorter exposures make sense for L

If possible, I always like to have at least half a dozen subs for each of the RGB filters so that the rejection algorithm has some data to work with.

I believe the theory that says our eyes are more sensitive to Luminance than Chrominance so I always go for lots of Lum data. I have managed to salvage a couple of images where I had very little colour data. Stacking a good number of subs always seems to produce good results.

I tend to play with the data during the day when I'm out for a few nights. I check the S/N ratios and can make a call on how much more data I think I need. After the first night imaging NGC 253 I realised I didn't need much more colour, so I mostly concentrated on Lum for the second night.

I also put a lot of effort into good calibration data. I redo my library every few months and normally use 500 bias frames and at least 24 hours worth of dark frames for each sub length. For flats, I always get enough to give me approximately half a million electrons which is the point of diminishing returns on my sensor.

So, that's a few of my thoughts. Hope they are helpful...

Cheers,
Rick.