M83 - The Southern Pinwheel

SpaceNoob (Chris) · #1 13-04-2015, 12:27 PM

Hi All,

I had a bit of a mission with this one, capturing subs between clouds! Having to contend with shallow well depth and a strong core signal, I could get away with the shorter subs on this one. I had about 80-70% Moon quite close so that probably didn't help with SNR...

There could probably be a lot more detail discovered by aggressive sharpening but I want it to look a little more natural to preserve the colour in the dust lanes. That and I can never seem to get a handle on sharpening without destroying something that I want present and unharmed.

I'm pretty happy with it so far, not sure if I will be tomorrow, but I think it is an improvement on my last galaxy. Ticked off another goal too.... Adding some Ha to an LRGB galaxy!

Image details:
Telescope: CDK 12.5 @ f/8, 0.44" sampling.
Camera: SBIG STT-8300
Composition: LR(Ha)GB 310:85(60):35:60, 9.1 hours total.

Flickr:
https://flic.kr/p/r9KSUe

Astrobin (Does not seem to respect ICC - I don't know how to fix yet... anyone got tips for astrobin?):

http://www.astrobin.com/172086/B/

RickS (Rick) · #2 13-04-2015, 12:45 PM

The stars are a bit blobby at full res but a very nice M83, Chris.

I haven't found any solution for Astrobin stripping ICC profiles, unfortunately. I did report it as a bug a while ago but didn't get any response. Maybe we need more people to complain!

Cheers,
Rick.

SpaceNoob (Chris) · #3 13-04-2015, 01:14 PM

Quote:

Originally Posted by RickS

The stars are a bit blobby at full res but a very nice M83, Chris.

I haven't found any solution for Astrobin stripping ICC profiles, unfortunately. I did report it as a bug a while ago but didn't get any response. Maybe we need more people to complain!

Cheers,
Rick.

Thanks Rick, yeah I am not happy with the blobby brighter stars, I am seeing this pretty much all the time. Anything bright gets pretty blown out I am guessing it is a combination of sampling at 0.44" and having shallow wells? I need to find a way to process this out for future images. Is there a magic button?

gregbradley · #4 13-04-2015, 02:19 PM

Overall quite nice Chris.
Try shorter exposures like 5 minutes and see how that goes.
I am thinking your camera needs adjustment - the gain may need to be turned down a bit. Not sure if that is a user adjustable thing.

Also for processing try masking out the stars and treat it as a separate layer. There is a thread going on at this site that goes over the various ways of doing that.

The galaxy itself could be brightened lightly with curves to bring out the faint halo as its been processed slightly black clipped making it seem the galaxy ends where the colourful blue ends and it doesn't.

Greg.

RickS (Rick) · #5 13-04-2015, 02:27 PM

Quote:

Originally Posted by SpaceNoob

Thanks Rick, yeah I am not happy with the blobby brighter stars, I am seeing this pretty much all the time. Anything bright gets pretty blown out I am guessing it is a combination of sampling at 0.44" and having shallow wells? I need to find a way to process this out for future images. Is there a magic button?

I find that star bloat is a problem with the KAF-8300 even in a wide field rig (Tak FSQ-106ED.) I spend a lot of time in PixInsight fixing it. I think the microlenses on the sensor are partly to blame. If you find that magic button please let me know!

Cheers,
Rick.

multiweb (Marc) · #6 13-04-2015, 04:34 PM

Great colours. Very punchy.

strongmanmike (Michael) · #7 13-04-2015, 05:56 PM

Wow Chris, that's bloody excellent, very colourful, punchy and some lovely detail

Now, if you can just sort the fuzz ball pom pom stars...heck, you are on your way to stardom mate

Mike

Placidus (Mike and Trish) · #8 13-04-2015, 06:54 PM

Hi, Chris,

Just comparing your stunning job with our own previous effort, which we used to be rather pleased with. Wow.

The detail in the dust lanes right through the core is most impressive. Top shelf.

It is perhaps a teensy bit over-saturated. Otherwise, magnificent.

Best,
Mike

Rod771 (Rod) · #9 13-04-2015, 08:35 PM

Nice detail and lovely colours Chris!

Looking good!

SpaceNoob (Chris) · #10 14-04-2015, 09:58 AM

Thanks everyone, I think I'll try figure out this star bloat thing and see if I can get some improvement. I agree with the saturation too, probably a bit on the saturated side, also I see the clipping too (due to being a bit heavy handed on the curves). I have another version processed first that is completely different and more "hubble" like with even more detail in the dust lanes but I lost control of the fainter trails and background. Will see what I can do over the next few days to improve it.

The first version I was working on before it all fell apart a bit is attached if you're curious. Also in Flickr but set to private as I hadn't finished it so not sure if the link will work:

https://www.flickr.com/gp/92067259@N06/Gp8nqF

Cheers,
Chris.

alpal · #11 14-04-2015, 05:18 PM

Hi Chris,
it's a fantastic picture.
It's a pity about the enormous stars.
I don't think the STT-8300 has a gain control - like the QHY9m - so it can't be that.

cheers
Allan

Paul Haese · #12 14-04-2015, 07:17 PM

The star aside, you have a good field of view, good colour and good detail in the first version. I am not a fan of the second image further down the thread though.

The stars are quite odd. I cannot recall seeing them look anything like these in any other scope setup. Perhaps It might be the baffling or something in the CDK setup. Or the combination of both camera and scope. I'm sorry I cannot be of help to sort that.