Ngc 346

stars2go (Colin) · #1 30-10-2013, 12:59 AM

Hi Folks
Has been a while since I posted an image but I thought I would share this one. This is the nebulous cluster NGC 346 on the edge of the Small Magellanic Cloud.

The image is here... https://dl.dropboxusercontent.com/u/...CDK%208-16.jpg

Approx 10 hours exposure using a Plane Wave CDK-700, Astrodon Gen2 filters and a PL-16803 camera. Image is a composition of Ha (used as luminance) and RGB. Processed with CCD Stack and PS. Control of the HA to avoid ending up with a red blob was the main challenge with this image

Comments are welcome

Colin Eldridge

Leonardo70 (Leonardo Orazi) · #2 30-10-2013, 01:06 AM

All the best,
Leo

alistairsam · #3 30-10-2013, 01:37 AM

Wow, that is awesome. How Long were the subs and how did you tone down the red? Desaturate?
How faint is this?

Alistair

renormalised (Carl) · #4 30-10-2013, 01:48 AM

Just goes to show what a good scope can do...wonders

Nice piccie

stars2go (Colin) · #5 30-10-2013, 01:49 AM

Hi Alistair
RGB combined in CCDStack. First grey scale Ha layer added in luminosity mode. A second Ha layer was colourised and added in lighten mode. The intensity of the colourised layer and its opacity controlled the level of red in the image. In the RGB image the nebula was mainly blue and there was a strong tendancy for the HA to swamp that. All subs were 10 minutes.
I am pleased you liked it
Thanks
Colin

dvj (John) · #6 30-10-2013, 03:46 AM

Outstanding image. I need to do narrow field shots of each nebula complex in the LMC! Each one is fantastic in detail.

multiweb (Marc) · #7 30-10-2013, 08:59 AM

Wow! Monster scope and great result.

alistairsam · #8 30-10-2013, 10:06 AM

Quote:

Originally Posted by stars2go

Hi Alistair
RGB combined in CCDStack. First grey scale Ha layer added in luminosity mode. A second Ha layer was colourised and added in lighten mode. The intensity of the colourised layer and its opacity controlled the level of red in the image. In the RGB image the nebula was mainly blue and there was a strong tendancy for the HA to swamp that. All subs were 10 minutes.
I am pleased you liked it
Thanks
Colin

Thanks Colin,
With the colourised layer, was that added to the blue or red channel as this nebula is predominantly blue as in the image below? is it possible to create a synthetic luminance and then add Ha for a HaLRGB and thus preserve the blue?
http://images.nationalgeographic.com...33_600x450.jpg

I just had a look at the image on my PC and noticed the red and blue stars have white cores, is this a result of stretching? did you use a star mask?
just learning the ropes with processing so thought I'd ask.

That CDK-700 is one fine scope with a lot of zero's in the spec, zero backlash, zero pec, zero/no coma....
sigh..

Cheers
Alistair

renormalised (Carl) · #9 30-10-2013, 10:33 AM

Quote:

Originally Posted by alistairsam

that cdk-700 is one fine scope with a lot of zero's in the spec, zero backlash, zero pec, zero/no coma....

$200,000

stars2go (Colin) · #10 30-10-2013, 01:38 PM

Alistair
I just added the colourised Ha as a layer in lighten mode and used curves to brighten it to introduce only the lighter parts of the colourised layer into the image. Even then, I had to lower the opacity to stop the whole nebula going red. And Yes; cores of the larger stars are saturated

RickS (Rick) · #11 30-10-2013, 02:17 PM

Very nice image, Colin. I did a bi-colour version with a GSO RC10 a while back but yours is better

renormalised (Carl) · #12 30-10-2013, 03:49 PM

Colin, instead of trying for a colour image, why not just do a B/W one. Either a luminance image through a clear filter or Ha in B/W/greyscale. I think they look just as good, if not better, than colour pics

stars2go (Colin) · #13 30-10-2013, 04:44 PM

Hi Carl

Personal choice really, I am not that fond of grey scale images

Colin

gregbradley · #14 30-10-2013, 04:54 PM

Exciting image. I have never seen detail like that before in NGC346. I remember we exchanged some PMs a few years back. You mentioned you were going to mount the CDK on the back of a truck. Is that how you ended up mounting it?

Ha in this object would wreck the delicate blues and you have done that aspect nicely. The cost seems to be blue halos around the brighter stars. Perhaps that is coming from the Ha as luminance part of your processing.

I think if you added a star mask at some point in the processing, expanded a couple of pixels and feathered a couple of pixels would protect the stars from the Ha blending. Ideally some luminance would have been better than Ha and use Ha only as a lighten layer colourised as red and gently does it as you have done.

I know some use Ha as luminance and I occassionally add a tiny amount this way to add some more detail but usually its a colour wrecker and throws the colour balance off or weakens them a lot or both.
Greg.

stars2go (Colin) · #15 30-10-2013, 06:25 PM

Hi Greg
I was very appreciative of your thoughts back then. 2 comments

1. The back of a truck was a bad idea, which soon became very apparent. The scope now lives in a Sirius observatory about 50k south of Perth in what is best described as fairly dark skies, Bortle 3.5 !!
2. Image processing skills take a long time to develop (for me) and I am only part way along the journey

Thanks for the comment
Colin

alpal · #16 30-10-2013, 07:39 PM

Hi Colin,
A great image & similar to this one from ESO:

http://en.wikipedia.org/wiki/File:ESO-NGC346.jpg

I can't help feeling that another go at processing would be worth it.

Off topic:
are you considering adaptive optics for your telescope?
Such a large telescope should be able to operate the flip mirror quite quickly
& should give a huge advantage.

cheers
Allan

Rex · #17 30-10-2013, 10:09 PM

Spectacular image Colin. Thanks for sharing.

stars2go (Colin) · #18 31-10-2013, 02:16 AM

Hi Allen

I want to try AO. Have ordered a system from SBIG, I thought one supplier and it should all work together.... so I have already received STX-16803 and 7 pos filter wheel. AOX and Remote Guide Head delivery probably December. I see a lot of comments about AO, if you have fairly steady conditions, it makes the image much better... if conditions are not so good then the improvement is also not so good. Will have to suck it and see.

Thanks for the inspiring comments

Colin

alpal · #19 31-10-2013, 06:42 AM

Quote:

Originally Posted by stars2go

Hi Allan

I want to try AO. Have ordered a system from SBIG, I thought one supplier and it should all work together.... so I have already received STX-16803 and 7 pos filter wheel. AOX and Remote Guide Head delivery probably December. I see a lot of comments about AO, if you have fairly steady conditions, it makes the image much better... if conditions are not so good then the improvement is also not so good. Will have to suck it and see.

Thanks for the inspiring comments

Colin

Hi Colin,
That's great news - I hope the AO goes well for you.

cheers
Allan

marco (Marco Lorenzi) · #20 01-11-2013, 03:08 AM

Good one Colin, really great detail. 70cm aperture.. you made my mouth drooling

Clear skies
Marco