Narrowband imaging - And the creation of colour.... is it science?

[AndyUK]

I can't recall which "famous" astro-imager said it, but in one of his video tutorials he noted some dodgy star shapes... some he "fixed" and one or two he simply cloned out (shock horror!).  I certainly wouldn't have noticed (I doubt many would), and, as he said, he had no problem doing this as, in his mind, imaging wasn't science, it was about producing a "pretty picture".  Now okay, those stars he cloned out weren't Alnitak or 52 Cyg(!), but there's no denying that his resultant picture was very nice indeed... Which is, I believe, what many of us are trying (hoping) to end up with - Something that we're happy with and others looking at (in my case, especially my wife!), can say wow, that's beautiful.

So, on that basis, perhaps certain (many?) types of astro-imaging can (should?) indeed be classified as "art"... as is Photography.

Taking that a stage further, and perhaps another example, I know someone who's working on M31 at the moment, but unfortunately he's discovered his Ha data has trailed.  I gave him 2 options - track down the problem and retake the Ha (which, with our weather, he may not be able to get until next year) or leave it out and settle for an RGB this year and take the Ha next year.  However, there is of course a 3rd option - Using a reference image, he could potentially "process in" those Ha jewels...  Admittedly, he will always know that that's what he's done and if he did do it now (as a short-cut to get an image he'd like to post), I'm pretty sure, that he WOULD get the Ha next year and re-process/re-post, but it would still be a pretty picture either way...

HOWEVER, I would most definitely agree with the other sentiments in this thread that if processing colour in to a mono image, it must be listed in the details (ie in the M31 example above, perhaps "Ha regions added in post-processing").  From my own personal view as long as people aren't being mislead or lied to, then there's no problem at all, but if they are then they should be thrown to the lions...! .

[ollypenrice]

The term 'pretty pictures' is a put- down. Any imager is perfectly entitled to be self deprecating and apply the term to his or her own work if they choose to do so but on the rare occasions when someone has asked my if I 'just take pretty pictures' I've given them a pretty robust response along the lines of  'No I B well don't! I try to make beautiful, accurate  and informative pictures of nature's marvels and I work hard at that. If you want a pretty picture go and take a snap of a Barbie Doll sitting on top of a Christmas tree.'

Did Van Gogh set out to make pretty pictures? Did Rembrandt? Goya? We astrophotographers don't have their talent, that's not my point, my point is about our intentions. When I see people working on images here with love, care and, above all passion, I wouldn't say to them, 'Pretty picture, well done.' (Most of them are bigger than me!!! )

Olly

[swag72]

10 minutes ago, ollypenrice said:

.....I try to make beautiful, accurate  and informative pictures of nature's marvels and I work hard at that. 

Herein lies the rub for me I guess Olly - Is the image of the Rosette  a beautiful picture? ..... I'll let each person decide on that  
Is it accurate? No I don't think so as the colour is arbitrarily placed where I want it and where I think it should be, based on other internet images and my own ideas.
Is it informative? Not in a sense that I would consider informative .......

 

[ollypenrice]

But since you've declared your method and your intention then that's fine.

I'm not sure about how I feel about basing a colouration on copying another image, though. Long term, where would that take us?

Olly

[swag72]

I guess that for this process development Olly I was playing it safe and trying to get something that was close to a genuine HST image.

Perhaps for the future, I will be more cutting edge  and put the colour where I like not where commonly viewed images suggest that they should be...... Onwards and upwards....

[cuivenion]

I was doing an outreach event about two weeks ago (my first), and I was getting questions along these lines. 'Do people just add the colour to these photos or is it real?' I think it it was. Since my only real experience in astrophotography is in planetary imaging my answer was no people don't add colour.

If false colour is being added I think it needs to be boldy stated and there has to be a line drawn between art and science. I've noticed that a lot of solar images state they have had false colour added presumably to bring out more detail, but not so many DSO or planetary images.

 

[Starlight 1]

This is a real nice post and Very interesting, what is my opinions, if I used a picture to  solve in everything being equal the copying process is already begun

Your personal touch on the process then make  it individual So as long its signed off in your name that what counts.

You could take a colouring book it's already map out what colours you apply is an individual taste someone who is colourblind would use different colours to you no right or wrong it's about having fun.

[Stub Mandrel]

I think its interesting to compare x-ray or radio 'false colour' images with Hubble or other 'visible spectrum' images.

The x-ray/radio images often have ghastly gaudy colours fully saturated and stretched right across the spectrum. they are usually awful to look at but get across the distribution of elements or signal strengths very clearly.

this suggests to me that the presentation of the Hubble Pallette, for example, is not just about getting across information on the distribution of gasses but is also informed by a pretty hefty aesthetic element that may or may not be related to seeking a 'wow' factor for any number of reasons.

 

[steppenwolf]

Quote

Since my only real experience in astrophotography is in planetary imaging my answer was no people don't add colour.

If false colour is being added I think it needs to be boldy stated and there has to be a line drawn between art and science.

No bubble burst here, I don't think imagers normally add colour, they just adjust a colour range to suit their own interpretation so you didn't give your outreach members any wrong information.

What Sara is doing here is a clear departure from the norm and she's made that clear from the start. Without a doubt, declaring the process is important for integrity just as we imagers already do when we decribe an image as being 'LRGB', 'SHO', 'NB', 'bi-colour' etc.

[opticalpath]

I very much liked the distinction that Olly drew in a recent post between processing that reveals - but does not invent - information.  I hope he won't mind me paraphrasing part of what he said:

" .... The information is in there. You don't invent it, you separate it.  ....... However, the separation is in the data to start with.  That's vital."

I think that is a pretty good rule to live by if we want to call what we are doing 'astro-imaging'.  When we assign colours, we do so based on a real separation of information within the data we captured; there are many wonderful examples of this being done in imaginative ways in our imaging forums.  I could imagine extending the idea even to colour separation based on some other factor such as signal intensity, if that added interest to how the data was displayed.  But the moment that we 'paint' colour in a more arbitrary way that doesn't represent real separation in the data that we captured, I think we crossed a line.  I have no objection at all to anyone doing this for aesthetic reasons as a piece of art, but I'm uncomfortable about it sitting in an 'imaging' forum, even if the process is fully disclosed.  It just feels to me like it belongs in a different category. 

Adrian   

[Stub Mandrel]

One good test might be how people react to pictures of nebulae with the stars removed.

is it purely an aesthetic exercise, does it reveal structure without distraction, or is it full of artefacts that minimise its 'scientific' value?

[glowingturnip]

I had some fun a while back, during a data-starved period of mine, with processing some raw Hubble data of the Cats Eye nebula.  I found Hubble data from 9 different narrow-band filters, some rather exotic deep IR or UV along with the regulars, and had all sorts of fun colour-mapping them in different ways.

I opted for this one in the end, I used a hybrid colour palette  based on NII=red, Ha=green and OIII=blue, but encompassing all 9 Hubble filter data channels in spectral order (scaled then from the larger spectrum scale linearly into the visible spectrum scale, and then pro-rata'd each channel into the nearest R, G or B (and I think i fudged the deep IR and UV straight into R and B respectively).  Looks quite nice I think.

Is it pretty ?  Yes.  Is it science ?  No.  (is it my own work ?  No !)

 

On the broader question though, I'd say that even the very best images on here are woefully inadequate as scientific representations of the target.  We're presenting data in 3 simple colour channels, in visible light only, with no meaningful spectroscopic data whatsoever.  Even NB photos only show 3 spectral lines out of the thousands coming from the target so only give a true scientific representation of those three lines.  On that scale RGB images are as equally valid in presenting a true scientific representation of the average light in each part of the visible spectrum.

[Stub Mandrel]

4 minutes ago, glowingturnip said:

On the broader question though, I'd say that even the very best images on here are woefully inadequate as scientific representations of the target. 

Not sure about that - there is scientific value in anything that allows the viewer to develop a concept of the structure of an object.

The value of Lord Rosse's drawing of M51 discussed elsewhere was huge, yet despite the enormous multi-server effort that went into it, it is only a sketch compared to the information in many images on this site.

Even my own humble M31 shows the surrounding globular clusters and where the younger, bluer stars are in relation to the older redder ones, and that helps me visualise the structure of the galaxy and by analogy better understand descriptions our own.