M16 Updated with RGB Data

[Hagar]

M16 captured last week but this time with 50 minutes each of RGB data added. This image uses the same Ha data as the previous Ha image but this time it is used as a purely luminance layer. Combined in CCDStack and adjusted in PSCS4.

The first image is the full frame, warts and all.
The second image is a crop of the core area.(Pillars of Creation)

Overall image Stats: HaRGB Ha = 60min, RGB = 50 min each all in 10 minute exposures.

[desler]

I really like the full frame, not 100% sure with the crop, the fainter stars look a little off to me! Although could be my bloodshot eyes.

Darren

[Omaroo]

The full crop is a ripper Doug. Really continuous tonal graduation throughout. Very well done. :thumbsup:

[ptc]

you have some nice data there but I can tell you that it is a mistake to use Halpha for luminance. It will attenuate the non-Hydrogen emission data, such as oxygen and sulfur and will therefore foul your color balance.

it is even a bigger mistake to use it for luminance for a tricolor emission line image.

if you take the time to think about what you are doing in technical terms perhaps you will understand.

here's a brief set of slides that illustrate graphically how Ha luminance skews color balance in emission line images but it does the same thing for RGB
http://www.narrowbandimaging.com/why_halpha_is_bad_for_luminance_pag e.htm

[Alchemy]

Nice detail Doug, bit of a stock answer, but it's true.

Re the use of ha as a luminence, I see Richards point BUT, I question the following, in particular as I use a one shot color camera

1. If the object is purely ha such as cats paw it's not going to make any difference.
2. In an object such as m16 which I presume to be largely ha in the nebulosity, what is the ratio of say ha to sulfur or other band in a luminosity way, in a one shot color the ha pretty much dominates anyway so is the difference really minimal.
3. People are happy to use non modded cameras to image m17 which makes a substantial difference to the image, and they are happy enough.
4. Given the ha makes the stars much smaller in respect to the nebulosity ( hope that makes sense) I think it's worth it to reveal that extra detail.
5. Any narrowband image is already fiddling with whats there, this is just another way of fiddling with it.

Imaging is really art in a way, one mans Picasso is another mans Rembrandt, and whilst Richards point is true, I feel that all imaging processing accentuates one aspect and limits another. So it's really an argument left to personal preference.

Clive

[RobF]

Good one Doug, but I'd also like to know more about the dark secrets of using Ha in RGB images. Its so tricky to get right. I loved the richness of the blues etc that people like Marcus make look so easy.

Enough of that - top shot!!:thumbsup:

[strongmanmike]

I see what Rich is saying too Doug, he has said similar to me on occassions :P. Your shot does look a bit monochrome red, it would look more pleasing if the blues were more influential, which is pretty much what Richard is saying..?

Great job though, I really like the wide field version, the monochrome red look works better here.

If it is any help David Malin thought the colour balance in this version (http://www.pbase.com/strongmanmike2002/image/63567656/original) was about right. Although not exactly as it appeared in reality, the actual print (http://www.pbase.com/strongmanmike2002/image/63568574/original) can be seen in this shot and was a little more magenta-purple..? David explained the reasons for the correct colour balance along the lines Richard has mentioned.

Mike

[jjjnettie]

Beaut work Doug. I love the full frame best, puts it all into perspective for me.

[RobF]

Was there any Ha in that 2006 rendition Mike?

[spearo]

Well done Doug,
Agree, full frame is very nice and shows the faint nebulosity captured.

Also had a look at your website. Bella is gorgeous!
frank

[strongmanmike]

Yes, it was an LRGB combine where Luminance (as L+R+Ha) was taken with AP152EDF Starfire and RGB (as LHaRGB) taken with an 80ED all using a SXV-H9 CCD.

Mike

[multiweb]

Nicely done. :thumbsup: Agree with Richard regarding Ha blend though. Have you read his paper? Makes a lot of sense.

[ChrisM]

Doug, for my eyes, the full frame image is very striking with great contrast between the background and the nebulosity.

Chris

[Paul Haese]

Doug nice work, maybe just bring the blues up a little and perhaps just take a look at those dark halos around the stars.

As for not using Ha for pure luminence; well I am in disagreement. I have used it several times and it took some time to get the blend right but it can and is often used by many astrophotographers. Rob Gendler is one I can think of as using it often for luminence and in tri colour emission lines. He even has a technique for sorting the balance. Technically I am sure Richard is correct but this is often as much about art as it is about science.

[ptc]

I am not impressed with Gendler's work; It always looks overprocessed to my eye and I don't buy using Ha for luminance. It helps accentuate some detail but at the expense of fouling the color balance and severely attenuating data that already trends to being too faint at the outset (oxygen and sulfur to be specific). People work like hell to get the sulfur and oxygen data that is already orders of magnitude fainter than the hydrogen and then they turn around and attenuate the faint by adding Ha as luminance atop it. It ought to be plain that this is a mistake if you take the time to think about this analytically.

I simply don't care for the overprocessed look that is becoming all too common: sort of like a bad flu that is making the rounds, keeps getting passed from one to another :-)

We can agree to disagree on this and you can do what you like of course.:thumbsup:

I do agree that this can be as much about art as it is science but if art is the goal then that ought to be stated at the outset and the result should NOT be called an image, it ought be called a painting or something else that clearly differentiates it from being an accurate reproduction of something real.

In my working definition of an image, that excludes things like painted in detail, sharpening due to the artifacts left behind and so on. I realize this is controversial and is goring a sacred cow or two, but this is my opinion and it is as equally valid as anyone else's opinion and when you have everyone saying the same thing no one progresses with any new ideas.

If you take the time to research it, you will find that when I pioneered the tricolor emission line method in widespread use today way back in 2001, I got mostly negative comments by those that didn't like it because it didn't look like Gendler's RGB.

but time has shown it to be a preferred method for nebular imaging, particularly from light polluted imaging sites that are far too common these days and were I have listened to the majority opinion at the time none of this would have ever happened

the moral of the story is that true breakthroughs start with a small group of people that dare to do things differently. It was true when Columbus sailed west to go east, it happened when Copernicus challenged The Church with his heliocentric view and happened when Einstein theorized that Newton's mechanics were only a special case

I am not for one moment representing that this work of mine approaches the work of these giants but I am saying that groupthink is often wrong and history has shown that to be true many many times. I further assert that this is yet another example of groupthink being on the wrong track.

[ptc]

Spot-on regarding that comment on the Blues.

In fact you will find that when you use Ha for luminance or even Ha + Red that you kill off blue reflection nebulosity

Jim Thommes reprocessed a nice image of M8 at my suggestion that he took and ditched the Ha luminance and found that a patch of blue reflection nebulosity appeared in his image that had heretofore been attenuated so badly by the luminance layer as to be imperceptible.

That work was fully documented on the Astromart Forums during April or May if I recall correctly.

[TrevorW]

It might be an idea to continue this debate in another thread and get opinions from others such as

Martin Pugh
Ken Crawford
Tom Davis
etc etc

IMHO the red is very prominant and star colour is lacking eg white stars but it is a fine image none the less

[Hagar]

Hi all and thanks for all the comments. I probably should explain this image/picture/painting, whatever it should be called.

It is just purely and simply a combined image of M16 Using a Ha mono image to try and bring out some of the detail captured by the Ha and impress it onto the RGB data which was captured with normal RGB filters.

It was not an attempt to enforce any scientific principles or details, I only intended or at least hoped to get an image which would show a bit more detail. After looking at the image it is rubbish and quite soft looking. Maybe I should only post when I have been asleep for a few hours after the initial process. It is amazing how bad it can look after a sleep.

I really appreciate all the remarks from everyone here as it is the only way I will learn how to present a decent image.
I do however have to agree with quite a few comments about the subjective colouring of astro images. Whether we like it or not the colour balance of images taken here on earth are a variable thing. Things such as atmospheric conditions, water vapour, dust etc can make a huge diference to the final colour of an image. As Mike pointed out David Malin regarded his image as the correct colour but what and who is to say David is truely correct. I doubt any colour balance techniques used by David can possibly be truely accurate for every image in every imaging condition.

I also have some problems with comparing RGB and Tri colour NB images as the two are in reality a world appart. I may be wrong but I understood NB imaging was a method of highlighting detail in Nebulas etc.
RGB on the other hand is probably a little more realistic in relation to the true look of the nebula but processing does fall back to what we think the colour should be and how much of each we need to make a pretty picture with good detail.

Neither of the two imaging methods are truely scientific in the end formatted image. Taking all this into cosideration I see no real point in argueing the symantics of of one method or the other and see no reason why a blend of one or both methods shouldn't be used to produce a pleasing image rich in colour and detail. It must be remembered that we all image with a differeing perspective on the final product and as such end up with different results. Personally I like and image which shows great detail and can only recall a couple of images posted by Mike Sidonio in comparison with hubble images and a couple posted by Rolf reflecting the same comparisons and set my goals to come up somewhere near their standards.

We are fortunate to have some great imagers at our disposal who are happy to help those of us who need the help and aai will continue to strive for a better image with their help and as can be expected I will stumble along the way and produce the likes of these images which should have been dumped but by posting I have learn't something else either to do or not to do on the next image I work on.

By the way, the next will be adding some colour to The cats paw nebula.
Just watching the images roll in and there is some horrible reflections in the Blue, green and Lum images. Something else to fight with and work arround.

I have added the (First) RGB only image and a (second) LRGB image made with a synthetic Lum made from the RGB channels. I like the stars better Trevor.

Thanks everyone for your comments and assistance.

[ballaratdragons]

Regardless of who says what colour is correct, or whatever opinions are given . . . I like the images Doug :thumbsup:

They are very good . . . err . . umm . . . paintings :rolleyes:

[Tandum]

Doug, if you did a non linear stretch then to some peoples eyes you have destroyed the true content of the image. If you played with sharpening to give the image depth instead of having a flat pavement look, then to some peoples eyes you have destroyed the true content of the image. etc etc etc

There is no science here, as soon as you do a non linear stretch all the science is gone and it's an art.

[Alchemy]

Rembrandt it is then

[desler]

Science, pretty pictures or whatever we want to call our offerings, one thing can't be underestimated, the last two repro's are quite simply wonderful.

Easy to get lost in, and very subtle differences and show a level of dedication in capture and skill in the processing.

In the end we all spend a considerable amount of time doing what we do, because we enjoy it. The learning curve; or should I say for me the learning steep mountain continues at different levels for us all and I for one will continue to post my tired eye versions that quickly get repro'd.

For me, watching the evolution from capture to final production holds its own fascination, it's not that long ago terms like "stretching", "levels and curves" and "selective sharpening" meant absolutely nothing to me.

We're all on a journey, one that we all entered into voluntarily, so let's not get to technical, experiment, show others and continue on what I can see will be a lifelong curve of improvement.

My 2 cents worth!



Darren

[strongmanmike]

I have heard this line before but it is just not true, sorry Robin.

Revealing faint galaxy extensions (http://www.pbase.com/strongmanmike2002/image/97061387/original)or jets (http://www.pbase.com/gregbradley/image/125180001/original), inner galactic structure (http://www.pbase.com/strongmanmike2002/image/108349883/original), outer bits of a planetery nebula (http://www.pbase.com/strongmanmike2002/image/122195818/original)or faint ghostly rings within nebulae (http://www.universetoday.com/35845/giant-soap-bubble-in-space/)that have either been seldom or never seen before, to either discover them or to chart their expansion or changing structures are all things only possible by stretching and manipulating your data...depends on what your deffinition of "science" is huh?

Poo hooing what we do as just "pretty pictures" is really a little naive (not directed at you Robin :))

Mike :thumbsup:

[RobF]

Is the Mark I Eyeball truely linear?
Even if it is, its able to cope with an amazing dynamic range.

Oops. Sorry to be chatting on your thread Doug. :thanx:

[Garyh]

Well Doug, regardless of the color balance/science? debate, you have captured a wonderfully crisp and detailed image and have manipulated the data nicely.
I reckon the color balance is a more personal choice thing...
If Martins, Tom or Kens or Mikes etc etc looked exactly the same in color balance wouldn`t that be boring ?

[Jeffkop]

Geeze Doug, I think the moderators are going to have to add "no posts about colours" to the banned list. It all comes down to exactly why a particular individual is involved in this persuit as well I think. To expand on that, I think both your images are fantastic to look at AND they are full of detail and if they were mine, Ide consider the time I spent collecting the data worthwhile. Everyone has their own take on images for sure, you yourself have even had a shift from your original critique, so these things are a changeable feast. Seems a pity that for some a technical viewpoint is first and the vista is a very secondary consideration, but its all about why one takes astrophoto's isnt it. Passion is a truely a force to be reckoned isnt it.

[TrevorW]

Hi Doug

Had a play with your TIFF file, there is really good data there, don't see anything wrong with using HA in this as come up a treat IMO but other so called knowledgable people may think different but DILLIGAF, hope you like

Cheers