Eagle Nebula - M16

Grahame (Grahame) · #1 17-07-2011, 08:11 PM

Hi All,

This is taken from a dark sky site in WA, consisting of 10 x 10min Luminance, 10 x 5min RGB (bin 2x2) stacked in CCD Stack, processed in photoshop.

Used a DSI RC10C and a qhy-9 mono (astronomik type IIc filters) for this. Not happy with the contrast of this shot - not sure where i went wrong (stacking or processing) but thought i would post it anyway to see what others think of it.

Link here to larger version.

Grahame.

beren · #2 18-07-2011, 04:43 PM

Very nice Grahame sharp and great star colours wonder if you can brighten the neb a bit more...well done

TrevorW · #3 18-07-2011, 08:25 PM

Have to agree with you Grahame does looks a bit soft

Ross G · #4 18-07-2011, 09:10 PM

Hi Grahame,

I like the all the detail and the cool star colours.

Thanks.

Ross.

irwjager (Ivo) · #5 19-07-2011, 09:00 AM

Hi Grahame,

That's a very respectable shot indeed - lots to see.
Could maybe use a bit more contrast, like you said to bring out some more detail, if that's your thing - it all depends on what you want to highlight.

The theory I go by is that, on first impressions of an image, the eye is drawn to the areas with the smallest details, so shrouding small detail somewhat draws the eye to larger structures. It's not necessarily a bad thing.

One thing I was wondering about the star colors though, there seems to be an over-representation of yellow stars, with not a red star in sight. Might there be a reason why this is the case? The spectrum range (in RGB) where yellow stars actually turn up really looking yellow is very narrow, so you don't tend to see many. If this is not a pure RGB image then, of course, all bets are off

Cheers,

Hagar (Doug) · #6 20-07-2011, 07:51 AM

Quite a respectable image Grahame. My only real critisism would be the star halos. They make the nebula sink into the background and take the zing out of the nebula. You could try reducing the stars a little. It is a hard target which is quite dim and has lots of bright big stars to contend with. All up though a nice job.

multiweb (Marc) · #7 20-07-2011, 08:39 AM

Nice shot Grahame. Colors are spot on.

gregbradley · #8 20-07-2011, 08:05 PM

Hi Grahame,

I had a bit of a play with it and it came up nicely so I think it is primarily in the processing.

Firstly your image is slightly black clipped. Have a look at the histogram for the image. You'll see the histogram is hard over to the left with no space. Always leave a bit of space on the left. One rule is to leave a bit of room there that you can trim up when you are near the end of your processing. In your case it means that some of the detail in that black dust cloud is lost as it has been cutoff. So watch your histogram when processing or at least make sure you leave a fair bit of space on the left side of your histogram. Almost any astroimage will have a little room on the left with a bell curve slimming out to a little wriggle along the bottom. That little wriggle is the faint detail in the black areas and you want to keep that.

This was a quick processing rundown I did. Firstly the first thing is the image looks a bit dull. You got some nice data there but it looks dull.
The Eagle Nebula is a bit like that. To get a vibrant Eagle Nebula is a bit tricky as it is surrounded by lots of Ha areas and a large blackish dust cloud. So:

1. Make a duplicate layer - set to soft light and opacity to about 15% or maybe 20% to increase contrast.

2. Use curves to brighten up the now more contrasty image.

3. Use shadows/highlights to bring up the contrast in the central area. I got it so the eagle itself showed up nicely. Play with those sliders a lot.
Generally the top one is set to only about 3, the 2nd about 2/3rds across the 3rd about 1/3rd to halfway.

Then highlights across to suit, then the slider below it about 2/3rds and then the 3rd almost acts like a focuser, usually sharpest detail is at about 1/4 the way across.

Increase colour correction about 20% and a touch of mid colour contrast as well.

Now your standard high pass filter contrast enhancement. Duplicate layer/soft light/high pass filter worked best at the higher numbers to include more of the structures.
Now layer/hide all/ brush tool set to 30% rub on the central parts only then flatten image when you have it like you want it.

Then the stars take too much attention in the image.

2 runs through of Noel Carboni's make stars smaller action did a nice job.

That's it. It now looks a lot different to the original and apart from the clipping which can't be repaired it looks pretty nice.

As far as the star haloes - I didn't mind that. There is a method to deal with this. Jase did a writeup a while ago. I haven't used it yet but it sounds like a good method. I thought the haloes looked fine as they make a statement that those stars are really bright but its not everyone's cup of tea.

Greg.

Grahame (Grahame) · #9 13-08-2011, 12:30 PM

Thanks All,

After a brief break I have applied some of the suggested actions to this image, also discovered why it was black clipped - I was taking the result out of ccdstack with the file-save scaled data option.... BAD IDEA

the file-save data option will do automatic pixel maths and came out much better.

multiweb (Marc) · #10 13-08-2011, 12:43 PM

Quote:

Originally Posted by Grahame

Thanks All,

After a brief break I have applied some of the suggested actions to this image, also discovered why it was black clipped - I was taking the result out of ccdstack with the file-save scaled data option.... BAD IDEA

the file-save data option will do automatic pixel maths and came out much better.

There's an histogram in CCD Stack now. Before you save as a scaled TIFF make sure you have a bit of room on each end to play with. Older versions used to clip - true. But I haven't had any issues for a while. What version are you on now?

Grahame (Grahame) · #11 13-08-2011, 12:47 PM

I only *just* got the latest beta version and i did have the histogram up this time round

they are getting much better with the tools and information available to you as your processing I can see.

multiweb (Marc) · #12 13-08-2011, 12:52 PM

Quote:

Originally Posted by Grahame

I only *just* got the latest beta version and i did have the histogram up this time round

they are getting much better with the tools and information available to you as your processing I can see.

Yes. I get the beta version exe for testing from Stan. The latest stuff is unreal. It's gone a long way. I really like some of the new features. The main histogram is the Lum (black one). Check your channels histograms as well. They're the ones that might be clipped.

strongmanmike (Michael) · #13 13-08-2011, 01:06 PM

Both versions look pretty good Grahame, the colour is pretty well spot on in both to me. The original version has a slightly more depth though but the later has more vibrant colours.

Nice job!

Mike

Grahame (Grahame) · #14 13-08-2011, 01:15 PM

Thanks Marc and Mike,

I will check the histogram colour channels - dont think I did that one

Mike - Got a real nice set of filters from someone which I think is helping there!

multiweb (Marc) · #15 13-08-2011, 01:20 PM

Quote:

Originally Posted by Grahame

Thanks Marc and Mike,

I will check the histogram colour channels - dont think I did that one

Mike - Got a real nice set of filters from someone which I think is helping there!

Yeah it doesn't exactly work like PS. I guess because of the offset slider in the color adjust settings. You can have a Lum that looks ok while the blue is clipped so blinking through the channels and stretching to include the widest is the way to go.

Grahame (Grahame) · #16 13-08-2011, 01:28 PM

excellent suggestion marc - I have also found that it is very true when they say you can scale darks down but not up - it has done horrible things to my images while calibrating them with the incorrect dark file.