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M31 re-edit

MartinB

By MartinB
in Imaging - Deep Sky

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MartinB

MartinB

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Promised my first clear night for around 6 weeks so all geared up but lots of high cloud so... nothing else to do but mess around processing.

Here's an M31 taken at Kelling using an ED80 and QHY8 Given it a few tweaks. Not sure how far to go with the saturation, gets difficult to judge after a while. The first is relatively lower sat the second a bit more. Any preferences?

11926_normal.jpeg

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11927_normal.jpeg

(click to enlarge)

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MartinB

MartinB

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With my aged laptop screen I am struggling to see any difference...

Guess I'm dancing on the head of a pin!

Thanks Kevin and Thing, one all then :)

There is a compressed tiff somewhere on ukastronomers Jamie, you can have a play with the raw data if you like or feel free to use these jpegs. Just let me know what adjustments you make.

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MartinB

MartinB

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Thanks for the feedback guys, very helpful and encouraging. The difference was a bit more marked before posting. I preferred the 2nd one but I think I was in danger of getting carried away and over doing things. I'll leave it alone now!

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Sam

Sam

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They're pretty hard to tell apart but I reckon the first one has slightly more defined dust lanes whereas the second one is showing more of the fainter blue bits. I think the second one is just a tiny tiny tiny bit better than the first because the fainter detail shows up better and it has a nice full look to it. :)

Sam

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Tim

Tim

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It's such a subjective thing Martin! And then there is all the varying laptop and monitor calibrations to take into account.

On my laptop screen, which incidentally is calibrated to the same degree as Mike's (Yfronto), the first image appears to have a little more contrast, and the second, a more delicate and fuller feel. Do you find that the problem with increasing the saturation is that it highlights also the halos around the stars? But it's difficult to get the stars showing their true colour without doing that. Incidentally, the colours in the stars is the biggest difference I have found really when swapping from DSLR to 16bit CCD. Have those extra thousands of colours to play with really gives the camera a chance to show some differences in them.

The other thing with M31 is the Ha regions. They seem few and far between, but perhaps they are just easier to see face on as in M33? They are present in m31 though, and its difficult to bring those out amongst the dust I find, as they dont seem to have the usual magenta/red glow.

One thing I noticed on your tiff Martin, was the colour cast, slightly on the yellow side. Did you use a LP filter at Kelling?

I prefer the second image btw :)

Tim

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MartinB

MartinB

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TJ the biggest problem I normally find when I increase saturation is introducing noise. With 4 1/2 hours of data I felt I could push the saturation a long way without noise becoming a big issue. I'm not really used to that luxury! Coloured halos are definitely accentuated, that's where the smudge tool comes into its own!

I think the QHY8 does give a yellow cast if no colour weightings (a boost to the blue) are applied when debayering. Conveniently the idas filter seems to correct this quite nicely! I wasn't using an LP filter at Kelling.

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ollypenrice

ollypenrice

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Who cares about the difference between the two? It's the difference between yours and anything I've managed that is rather overwhelming! These are great, with bombing dense colour.

But I do prefer the first on such moments as the seeing permits...

Great stuff,

Olly.

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Tim

Tim

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ah thats interesting. I havent used the camera without a cls filter which also highlights blue.

For noise, have you tried GreyCstoration? Its slow, but seems very effective when used sparingly, better than any median noise filters.

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MartinB

MartinB

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For noise, have you tried GreyCstoration? Its slow, but seems very effective when used sparingly, better than any median noise filters.

I've never heard of it TJ. I use a mixture of Noel Carboni's actions and my own noise reduction using very small gaussian blurs to selected areas of the image - typically between 0.4 and 0.8 pixel radius.

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Tim

Tim

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GreyC is available as a standalone, but I think there is a plugin for maxim. I have it in nebulosity too. I first came across it using the amazing Pixinsight. The algorithm it uses differentiates between sharp edges and background noise. It works a treat on colourful noise, as when increasing saturation.

Here's a link. http://cimg.sourceforge.net/greycstoration/ worth a try, but it has a lot of settings to configure.

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