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davesparx

A tiny Owl :(

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Hi there,

This is last night's Owl nebula. It's tiny!

Is there supposed to be any colour in this nebula?

I've converted to .jpg but it looks like the resolution is low?

It's ED-80 with focal reducer on NEQ6 with finder guider.

David

post-19599-0-82024200-1388485836_thumb.j

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With my 10" SCT and Atik 314L it looks a greenish colour but that may just be in the processing, and obviously lots bigger.

Dave 

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Have only attempted this once and was a pretty poor effort. With only a LPR filter and using a DSLR mine appears a little on the green side

post-15439-0-46799400-1388500732_thumb.j

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i didn't get many lights on it but to me it seems a pale turquoise with a subtle red hue at the edges

owl_stacked_zps337f8cff.png

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You've got a nice sharp image there, how many exposures is it made up from?  Perhaps with a bit of processing of the colour balance and addressing the vignette gradient, the colour will show through?

It is a very small object but interesting nonetheless.  I had a go at imaging it a couple of years ago and framed it with the nearby M108 galaxy through a 70mm frac + QHY8:

post-5202-0-40485000-1388509769_thumb.jp

Edited by r3i
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Processing can result in almost any colour you wish.

Your entire frame appears very red/purple this is the kind of effect I get from the light pollution filter which also is fixed through processing but could also be down to optics.

There are many variables that can effect this, so I always feel that colour is very subjective and mostly user defined.

You mention using an NEQ6 and ED80 but what camera did you use? I'm assuming from the frame size a dslr?

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Astrophotgraphers working in colour don't invent their colours, though. They should have a bearing on reality, though it's hard to be perfectly calibrated all the time and there will be variations. The OP's image isn't calibrated in colour balance because the background sky isn't a neutral dark grey.It has a strong magenta caste, suggesting that the green channel needs lifting.

The first step in colour balancing should be to look at the top left of the histogram peak in each channel. They should be lined up. You can adjust them by clipping back the black point (moving the left hand slider to the right.) Don't cut into the main pedestal though.

levels%20aligning-L.jpg

In a colour balanced image the owl will be a blue-green colour with some red structures. This is because it has strong O111 signal and some red Ha features.

Olly

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Hi there, chaps

Thanks for all the information and advice. Anweniel, I'm using a modded canon 1100d. Olly, I didn't know that they should be lined up...I've been messing around with them to try and get the background as dark as possible. I'm guessing that that puts loads of blue into the photo?

I'll have another go at processing he subs that I have.

Thanks, chaps

David

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Hi there, chaps

Thanks for all the information and advice. Anweniel, I'm using a modded canon 1100d. Olly, I didn't know that they should be lined up...I've been messing around with them to try and get the background as dark as possible. I'm guessing that that puts loads of blue into the photo?

I'll have another go at processing he subs that I have.

Thanks, chaps

David

It tends to be a beginner's mistake to go for an ultra dark background. I would suggest a background sky set at about 23/23/23 in Photoshop for the R,G and B channels. I think you'll find this looks much more natural. There is also a danger of black clipping (discarding) interesting faint data which deserves to be there in your picture.

Olly

Black%20clipping.-L.jpg

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Hi there, Olly

That's excellent! I can see that I have loads to learn. I can't wait to get out there again and give it all another try. What a great hobby!!

David

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Maybe my ignorance as Im still very much a novice but why make the assertion a colour imager SHOULD aim for an image that has a bearing on reality, is there no scope for artistic license?

Edited by Anweniel

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Maybe my ignorance as Im still very much a novice but why make the assertion a colour imager SHOULD aim for an image that has a bearing on reality, is there no scope for artistic license?

We're all free to post whatever we like! However, if you post an image as RGB then boring old convention would say that you'd put the red in the red channel, the green in the green...etc. Also that you'd use a red filter for shooting red...etc.  :grin:  :grin:  :grin: I think that if you post an image as RGB then it should be RGB. No? Of course, NB imagers (wild maniacs, the lot of 'em!! :eek: ) can do whatver they like.

I think it's a bit too simple to say that colour in RGB imaging is a free house. If it is, it ceases to be RGB imaging. But if you don't want to do RGB, then fine. I use artistic license all the time but...

- I want my background sky to be a dark neutral grey. Turquoise is out!!!

- I want my star colours to agree with the astrophysics and the HR diagram.

- I want Ha to appear in red, O111 on the blue-green border.

- Etc.

:grin: lly

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It's a reasonable assertion that when RGB imaging (or true colour) the colour of the object should represent how it actually appears. That's kind of the point in RGB. Yes you have liberty to process certain features if you want, but overall it should be a faithful representation.

More or less all bets are off for emission line, where transitions in atoms are represented by colour. This is a false colour if you like as if viewed by the eye it would not appear this colour. Any narrowband image will have weird colours compared to RGB. There is more scope of artistic licence.

There is a rather heated debate at the centre of all this, and that is whether imaging and processing is science or art. For me it is a bit art but a lot of science. I have a background in physics so this is hardly surprising. I take a scientific approach to imaging. I believe that knowledge of what's going on will lead to better images. If you trawl back through some of my posts almost all will have a scientific slant. That's because science is absolute (as good as) and it deals in facts and numbers. It's never subjective, always objective. In saying that I take an scientific approach, I don't actually do science with my images. I'm not a photometrist nor a spectroscopist. I'm in it for pretty pictures, obtained through understanding of the systems involved. That may change in the future, I'm not sure. It's hard to achieve Hubble images from the ground with a small apo.

Yet others view this as an artistic endeavour. That's completely their prerogative. It's expressionism on the grandest scale. For some, scientific integrity of an image is meaningless. And as with anything in art it's all fair game.

However both camps almost always agree on one thing, images of an object should be a true reflection of that object. Adding data for example is a no no. And why do we feel that restraint when it's all fair game in the artistic sense? Well because the universe needs to sexing up. Whatever it does naturally is far more grand than the mind of even the wildest dreamer.

There is artistic licence...to a point.

Thanks for watching! :)

Paul

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