The Lagoon: A pretty picture with some science.

[sjastro]

A combination of narrowband and true colour imaging to map out the dominant Ha, OIII and SII regions in the object.

Ha and SII where mapped to red and OIII to cyan.
The pinkish regions indicate strong SII emissions relative to Ha.
The redder the region the stronger the Ha emission.
Cyan /blue regions indicate a strong OIII emissions.

3hrs each Ha, OIII, SIII combined luminance, 1 hr each RGB.
BRC-250, STXL-11002 camera.

http://members.iinet.net.au/~sjastro/LagoonHa_OIII_SIIc.jpg

Clear skies

Steven

[multiweb]

That's a really superb shot Steven. Very good. :thumbsup::thumbsup::thumbsup:

[jase]

Well done Steven. What bandpass are your narrowband filters and did you need to subtract Ha from SII to get a cleaner (distinguished) emission line?

[Rex]

Nice job Steven, my two favourite subjects, science and pretty pictures. lol. Nice details and I like the colour even though it is a science image. Well done and interesting information.

[Atmos]

Fantastic rendition there Steven, I've got something to aspire to :-)

[Geoff45]

Beautiful rendition there Steven. Everything is good-- colour, stars, detail. Nicely done.
Geoff

[RickS]

Very interesting image, Steven. Also an attractive one!

Cheers,
Rick.

[Stevec35]

Nicely done Steven. Science or not it's an excellent Lagoon picture with intelligent use of NB filters.

Cheers

Steve

[strongmanmike]

Science..? well maybe, looks like just another (of the many) colour palette interpretation to me :question: which is nothing negative BTW.. but I agree with Steve C and it actually looks like gases, with a lovely tenuous gaseous feel, excellent :thumbsup:

Mike

[Slawomir]

It is a very pleasant experience to appreciate the nebula in you photo - nicely done! :thumbsup:

[sjastro]

Thanks Slawomir



Hello Mike.

The objective of this image was to highlight the Ha and OIII dominant regions in the the Lagoon. It is an LRGB not a narrowband image.
The process doe not involve mapping the data to a specific channel as in narrowband imaging but rather remapping the colours through Ha or OIII dominant masks that are applied to the colour image.
The science involves assigning the correct "colour" to the emission which is not the case for narrowband imaging. In fact most colour palette assignments in narrowband imaging are distinctly "unscientific" given that the data is not matched to the RGB channels according to its wavelength range.



Thanks Steve



Thank you Rick.



Much appreciated Geoff.



Thank you very much Colin.



Thanks Rex.




Hi Jase.

Given that Ha and SII are at 656 and 672nm respectively and are "red" emissions, I simply produced a combined Ha+SII image and subtracted the OIII data after normalizing the background to produce a Ha+SII dominant mask.
I use 7nm bandpass filters which now has me thinking the pink colours in the image may be due to NII emissions at 658nm rather than SII.

I will produce separate HaRGB, and SIIRGB images to see if I can spot any differences.


Thanks Marc.

Clear skies to all.

Steven

[strongmanmike]

Ok, I think I see now what you were aiming for here :thumbsup:

Either way, it is a really nice looking Lagoon.

Mike

[topheart]

Very well done Steven!

Looks natural to me as well ....Nice to see another imager with a BRC250 here.

Cheers,
Tim

[SkyViking]

That's just stunning. I really like this interpretation of the Lagoon, very well done Steve. The colours and subtle hues are great and the whole area looks very ghostly and beautiful.

[sjastro]

Thanks Mike, Tim and Rolf.

Steven

[sjastro]

Tweaked the Ha+SII mask to bring out further detail of SII emissions in the image particularly in the core region as seen in the before and after tweaking in the attachments.

Latest version.
http://members.iinet.net.au/~sjastro/LagoonHa_OIII_SII_newc.jpg

Clear skies

Steven

[Weltevreden SA]

Steven, you mentioned boosting the SII emissions relative to Ha as part of the science goal of the image. Was this goal to probe the SI column density [logN(SI) is 16.3/sq.cm in the Hourglass] as a gauge of emission intensity from the Her36? Garnett 1989 suggests that the N(SII)/N(SI) ratio is >3 for many Galactic cluster forming regions. It seems upon eyeball inspection that emission intensity is little different in the Hourglass core but discernibly brighter & more textured in the structures illuminated by Sgr9 (O4), esp the filaments N of the HG. The Teff of O7.5 Her36 is 36,000 K while O4 Sgr9 is 42,000 K. Her36 itself is reddened by 6.3 Mv by a local superimposed dust remnant but the Hourglass as a whole is only ~1.7. IOW, the added UV intensity produced by 6,000 K can be revealed by astute line selection in image processing. Was your goal to demonstrate this is the kind of science that can be drawn out of image processing available to most enthusiast budgets? If so, good show! =Dana in S Africa

[sjastro]

Hello Dana,

In short the answer to your question is no.
Since I am using RGB colour data along with combining Ha OIII and SII data in a luminance image, SII data is effectively being drowned out and very difficult to extract out as a separate colour mapping.
It doesn't constitute "empirical" science as some of the SII data is lost in the background.
Since the objective of this image to to give some indication of the breakdown of the Lagoon in Ha, OIII and SII emissions, loss of SII data is a consequence.
Extracting any SII data as a separate colour mapping is more artistic license than science. The science part comes in the construction of the mapping masks to extract the data.

The other issue is that while separate Ha and SII images look quite different (the left hand attachment is the Ha only image, the right SII only), the reason for the difference is that SII being a longer wavelength is able to penetrate deeper into the obscuring dust of the Hourglass.
Structurally the Hourglass is emitting both Ha and SII which is difficult to separate using pixel maths.

Thanks for your comments.

Steven

[rustigsmed]

very nice Steven, I particularly like the whispy details in the brighter sections.

Cheers

Russell

[sjastro]

Thanks Russell.

Steven