Anyone fancy a go at this image?

[broadsword]

I was very pleasantly surprised from a previous post where a stacked image of mine of the Bubble Nebula was greatly improved by a member - highlighting perhaps how much 8 bit GIMP processing is limiting my own efforts.

I wanted to try it out again with a galaxy image - these are the ones which I've got generally pants images from, with lots of noisy speckled spirals once I've sucked the background lightness out.

So, anyone fancy a crack at this image of NGC 2403? It is the DSS stacked image from 20x120 sec ISO 1600 frames, with darks and bias images but no flats (I'm moving to these on the next night out), plus I also did a bit of RGB algnment and saturation increase with DSS. I can see good detail on it, but as I said GIMP seemss to drain it.

I've saved as a png this time rather than a jpg as advised previously....

Thanks in advance

[billhinge]

Hi Neil

I had a go in Pixinsight but I'm no expert, I'm sure others can do better

Used crop, dynamic background extraction, histogram transform and atrous wavelet then a bit of noise cancel

[broadsword]

Thanks Bill(?), great effort. Is Pixinsight a paid-only option right now? I think there used to be a free version?

[Cloudwatcher]

We have guests arriving shortly so I have been told by SWMBO to stop playing and do something useful!

Anyway,heres what I've pulled out of the mist so far............still needs a lot more TLC but could be a goodun.

[broadsword]

Ah, Cloudwatcher, glad you came through. I know the feeling, but surely this is what holidays are all about??

Thanks for the first go, looks way better than my attempts, any more you could do would be phenomenal. Again, if you get the time, maybe a quick run through of the steps? I know I'm pushing the goodwill bit..

[Daniel-K]

try stacking it with biliner rather than automatic i have had the same effect were the vignetting looks like that and its down to the settings in DSS

[broadsword]

Hi Daniel, just got DSS running in bilinear mode right now. Whilst on the subject of DSS, my settings are a bit historical and arbitrary anyway. I'm using average to combine the lights, but median for the darks and bias. Good, bad, or indifferent? Anyone any thoughts?

[rfdesigner]

couldn't resist...

out of interest.. I take it you're stretching the file before posting?.. I assume you are because you've only posted an 8 bit image.

would be interesting to see how people here could get on with the un-modified 16bit/colour image as it is just post stacking.

Derek

[Cabbagey]

Put my very amateur skills to the test with the help of GIMP, got this:)

[Cloudwatcher]

See your galaxy in full living colour on a computer screen near you with........... CW VISION.......

[broadsword]

All, thanks for some marvellour efforts at this one, lot for me to think about.

CW, I see you got lots of colour out of this in the end, even some pink. I've seen this on some of the best CCD images of NGC 2403, but didn't see any in my attempts. Don't get any in things like M33 either, wasn't sure if the IR filter in my unmodded Canon cuts it out. You also got some sharp detail in the core, with some dark specks in there that I jast can't get - again, any chance of a quick run through of the steps?

Cheers

[broadsword]

couldn't resist...

out of interest.. I take it you're stretching the file before posting?.. I assume you are because you've only posted an 8 bit image.

would be interesting to see how people here could get on with the un-modified 16bit/colour image as it is just post stacking.

Derek

Derek,

I think it ended up as 8 bit as I converted it to a PNG file in GIMP! Here is the stacked version without any stretches - I converted it to a PNG again to keep the size down, however I don't know if it is still in 16 bit - how can one tell? I'm a bit new to photo processing...I have to use a function in Powerpoint to do the conversions.

[russellhq]

I like these posts, helps me with my processing techniques.

Here's my best effort:

[Cloudwatcher]

My last post was,of course, just a bit of (over sharpened) fun but on a more serious note there is quite a bit of colour to be found in the original image.

Never having used GIMP I don't know what tools you have at your disposal so it's a bit difficult to give detailed advise that you can use. I assume levels are available and a method for varying saturation but possibly not the Dodge and Burn facilities. The latter are very handy for bringing out detail when you 'go deep' on an enlarged section of an image.

By way of illustration the first image below shows a section where basic Levels and Saturation were used,the second is where Dodge & Burn tools,on an enlarged view,have been put to use. Really all one is doing is changing the contrast between light and dark areas but with more control at your fingertips.

[broadsword]

Hi CW, thanks again for the tuition. The Dodge and Burn feature seems to do the business - there is usually a GIMP equivalent, I'll do a Google search on it.

i think the thing that stands out the most in terms of the better results in your images is how the very faint stuff, like the outermost arms, stay smooth and noise free when you've taken away the background glow. In mine I just get a few random grey blotches of noise. Is this something where 16 bit would help? I've paid a tennner for Photo Plus X4 so I hope to soon find out...

[Cloudwatcher]

.......the very faint stuff, like the outermost arms, stay smooth and noise free when you've taken away the background glow. In mine I just get a few random grey blotches of noise. Is this something where 16 bit would help?

The short answer is,I don't know.

I do most of my stuff in 8bit mode in Photoshop mainly because in higher modes some of the tool are not available.The finished image can be converted to 16 or 32bit after but to be honest unless I zoom in I can't see much difference.......perhaps I should go to Specsavers!

Blotches of noise can be treated by isolating in a separate layer and using the blur tools in Photoshop,reducing,in the case of the galaxy arms, the noise to a smoothness that is acceptable.

A quick overdone example attached by way of illustration........this may result in the loss of a few stars if your not careful.

[broadsword]

Thanks for all the help CW, I'm finally getting results not too far off yours. I must admit, dodge and burn feels a little like cheating, a sort of hand retouching, but I guess it can only enhance pixels that are already there!

I actually used your oval masks when I was messing around as I found it stopped me losing all of the faint detail in the arms by not having to do the initial work to get rid of the background sky glow. I noticed everyone managed to get the background flat, often finding stars in the vignettes corners. Anyone got any tips on doing this, I really struggle trying to do it with levels and curves?

[rfdesigner]

To get a flat background caused by vignetting, remember the problem is a light problem, not an offset one.

This means you need to multiply or divide the image not add or subtract.

In IRIS, I used some of the susbky commands with masks to get the background fairly flat, but this is a subtractive process, so I then subtracted this flattened image from the initial image to get my 'flat' then I used that as a conventional flat (dividing the origional image by the flat) to get the image more properly flat.

With IRIS I found it almost impossible to get a true flat as the image I was working with had already been manipulated. With an origional stack it would be more straight forward.

Derek