IC 1848 "The Soul Nebula" in HST palette

[GordonH]

Hi all

I've almost recovered from my laryngitis and there was the promise of some clear weather last night so needs must as they say and I just had to get out and take some pictures. I decided to tackle IC 1848 as I hadn't tried this subject before, I was aiming for 2 hours per filter in 10 minute unguided subframes but as is usually the case with the British weather there was a couple of periods of cloud which wiped out 2 of the Ha and 1 of the OIII subframes. For the rest of this imaging run the seeing wasn't very good, I could just about make out Cassiopeia as the sky appeared a bit misty, this was confirmed by the noisy image and gradient on the image when processing which I think I have managed to get rid of the worst through processing (so please excuse the over processing). I colour combined the image as an LRGB combine using the Ha data as a luminance channel and then asigned SII=Red Ha=Green and OIII=Blue with a weighting of 3:1:2 for the respective RGB channels. Some people may say that this is wrong to use the Ha as a luminance channel when there is already Ha as a colour channel and this doesn't give a "scientifically" correct image, but I don't image for scientifically correct images I image for enjoyment and because I find the results pleasing. Anyway, that is enough of my ranting, I hope you like the image

Thanks for looking

Best wishes

Gordon

[thing]

Crikey Gordon. That's a bit good. Loss of data or not that's a mighty fine effort. I don't even know where that neb is. Looks like a woman's head with a ram's horns hairdo.

[Reggie]

Superb image Gordon, especially given the amount of hassles you had getting the subs in the first place.

[GordonH]

Crikey Gordon. That's a bit good. Loss of data or not that's a mighty fine effort. I don't even know where that neb is. Looks like a woman's head with a ram's horns hairdo.

Hi Dave

I should have mentioned that it is in Cassiopeia very close to the "Heart nebula"

Best wishes

Gordon

[LostNSpace]

Cracking image Gordon.......

Certainly one of the best Soul Neb images i have seen........

Mark

[Psychobilly]

Stunning Gordon....

I pay the pair (Heart and Soul) a visit from time to time but have yet to get any decent time on the soul as I got the dome aperture in the wrong place last time

If we ever get clear skies in the west of the country again I'll; have to re-visit it

Billy...

[MartinB]

Another great image Gordon and I love the colour. Pretty pictures is what it's all about really. Scientific photometric images aren't the sort you would put on your wall!

I'm very interested in the SII and what you've done with it here. I can't see any SII nebular detail The central area is magenta as are the stars there which looks like the red has been boosted and the green toned down. Is this due to different treatment of the centre of the nebula compared with the areas surrounding the nebula.

I'm still not convinced that the amount of time taken gathering SII wouldn't be better spent getting more Ha and OIII and then creating a synthetic 3rd channel. All the great stuff in this image is green and blue. What are your thoughts after processing it all?

[GordonH]

Hi Martin

To a certain extent I agree with you except that in a lot of emission nebula the different emission lines overlap each other giving a mix of colours rather than distinct areas of Ha, OIII and SII. I think this nebula has a mixture of both in that there are quite clear areas of Ha and OIII (green and blue) but as you pointed out there is a considerable amount of magenta colouring in the middle of the nebula and I think this is where the SII has contributed,ie red and blue mixed gives a purple/magenta type colour. As you say, an alternative would be to concentrate on the more dominant channels such as Ha and OIII and create a synthetic channel but this would create a completely different colour palette. I think it is basically down to personal taste really. When I do the colour combining in Maxim DL I always try different palettes and weightings until I come across a combination that I find pleasing to the eye, this was no exception

Best wishes

Gordon

[Doc]

Another oer I've never heard off but am mighty proud to be looking at it now.

Fantastic image Gordon.

[MartinB]

Thanks for that Gordon. I've done a bit of narrow band and my experience has made me ditch the SII, mainly because of the severe shortage of imaging time. I like your image a lot and interesting to know that the magenta is down to the combination of OIII and SII

[Taff]

Nice one Gordon' great colours of the neb.Taff

[narrowbandpaul]

hi gordon...

nice image...as usual.

I find O[iII] a more frustrating channel than S[iI[, since high energy events in the nebula arent that abundant (in the centre yes)

I find S[iI] shows up in compression quite well, and gives a 3D image.

yes the O[iII] and S[iI] are both weak, but for diffuse nebula I find O[iII] more annoying.

For planetaries, O[iII] is very strong, more so than Ha believe it or not....

For diffuse, I like the use of all 3 colours...

Ha as a kind of background, S[iI] to add data to compression regions, and O[iII] to map high energies...

gives a good 3d looking image I feel.

Also the KAI 16000 sensor has a reduced S[iI] QE compared to O[iII] so that in itself will alter the relative strengths of the lines.

Just my two pennies

Paul

[MartinB]

Very interesting points Paul. It would be good to continue the discussion but not at the expense of Gordon's thread so I'm starting another thread - "is SII worth the bother"!!!!

[GordonH]

Hi Martin and Paul

I don't think this discussion is at the expense of my thread, it is very useful information which helps myself and other beginners in NB imaging develop. In my particular image the apparent lack of SII data visible is down to several factors partly due to what Paul was saying, partly because of what Martin is saying ie "Is it really worth the bother" and also because of the way that I process my narrowband images at the moment.

At the moment because of relatively short exposure time due to weather, lack of free time etc, I also use the Ha as a luminance channel to help smooth the image when it comes to processing (I have tried with and without and I find it easier with the Ha as luminance). Now this is where the narrowband purists such as Richard Crisp throw their arms up in despair as their view is that you can't use Ha as luminance when it is already a colour channel as all you achieve is accentuating the Ha channel at the expense of diminishing the OIII and SII channels. To a certain extent I can see their point but in Richard Crisp's opinion there is no compromise, it must be done without Ha as luminance otherwise you don't have a "Scientifically correct" image (my choice of term not Richard's). The reason why I am mentioning this is because I think sometimes some people forget that what we are doing is Astroimaging/astrophotography which is a very rewarding branch of photography which in turn is a form of Art. As far as I am aware the whole point of art is to allow tthe artist to demonstrate his perception/interpretation of how a subject looks whether it be as a drawing, painting, pastel, photograph, sculpture, etc. Although people have different tastes the important thing is does the image look pleasing. I enjoy the end results of my imaging (otherwise I wouldn't do it) and so far judging from the amount of feedback I have received on the forums virtually everybody else does as well which is an added bonus (Richard Crisp still gives critisism about my use of Ha as luminance). I don't plan on changing my basic techniques because my images are "wrong". To me part of the enjoyment is experimentation and trial and error and as they say "There is more than one way to skin a cat" (no intention of any suggestion of cruelty to animals!)

I would be interested to hear what other people think about this

Best wishes and clear skies (please)

Gordon

[MartinB]

I wonder if Richard would feel the same living in Chesterfield, with a non permanent set up and working 60 hours a week!

Most of our problems come from getting adequate s/n. That is especially the case with narrow band. The weakest, least important channel holds back the rest of the image. If you have a strong luminence channel that will obviously improve the Ha detail visible. For aesthetic imaging I guess it is trial and error, seeing what looks best, which is subjective.

The main problem I have with luminence and narrow band is loss of colour saturation. I have some routines to deal with that with HaHaRGB images but NB is more of a challenge. You have good saturation in your image though Gordon