The Ghost of Cassiopeia, so difficult...puzzling

[fmeireso]

Ha, now you mention this Dietmar about coloring...it got me thinking,i just reviewed my OSC stack of the IC 63,

this is a plain OSC , no filter , no nothing....

I have colored stars, that seems all allright....but...not trace of red nor magenta on the Ghost...how weird...

I noticed in processing that only the outerlines of that object turned red if i oversaturate. You can see this on Stefans image too..the red is more in the outer parts of that nebulae. You see it better of course cause it is a astro cam, i believe.

Just brainstorming, I could be wrong...

IC67Snapshot.JPG (225.46 KiB) Viewed 3408 times

[Stefan B]

I remember our discussion on your Veil Nebula thread, and I have only now understood ( ) that you are using your duoband filter with your mono DSLR. Well, this means, that you cannot distinguish between Ha and OIII, right? I will have to think it over, this thread and your Veil Nebula thread.

Dietmar, I guess that approach is totally valid. You get the detail from both gases and color them via your RGB. This is basically the same as when I use my l-eNhance data as luminance and broadband as RGB (like here viewtopic.php?f=11&t=2653). When entering the l-eNhance data into the luminance slot ST converts the signal to b/w and color is only assigned afterwards in Color. The OIII signal then will be colored teal/blue and the Ha will be colored red. Freddy's take on this is even better since he uses a mono cam for the luminance and doesn't waste any photons.

Did you use the NBaccent module for your image Stefan?

Yes, I did. With the LRGB approach I wasn't getting the colors right. But with NBAccent there were stars everywhere

I noticed in processing that only the outerlines of that object turned red if i oversaturate. You can see this on Stefans image too..the red is more in the outer parts of that nebulae. You see it better of course cause it is a astro cam, i believe.

It was a modded DSLR.

The usage of an unmodded DSLR with Bayer matrix makes it probably pretty hard to detect any color from the faint Ha at all while your mono DSLR with the duo NB captures quite some luminance from it. I guess this pretty much explains your coloring lacking the red. The question is if it's possible to get some red out of your duo NB data. But that maybe difficult since it contains also OIII signal (and Hb but that shouldn't bother us since it's a weaker mirror of Ha) and you can't discriminate between the two with the mono cam.

As far as I know the object barely contains any OIII at all so it might be worth a try to use all the slots in Compose by entering the OSC data into RGB and the mono data into luminance and NBAccent. You'd get the clean signal from the duo band, the colors of the reflection stuff from the OSC and the Ha from the NBAccent slot (although contaminated by all the stuff from the OIII bandpass). As far as I know Ivo didn't encourage to use the same data for luminance and NBAccent but it maybe helps here...

You haven't shared to two data sets here, right?

Regards
Stefan

[decay]

I will reread Sven's thread and maybe post a hint about that

Oh, I've seen you already posted a hint in Sven's thread ... I will post later on there some thoughts why I'm thinking (alt least for the moment ) that the rings are diffraction rings.

I guess because the color info comes from the OSC not the mono

Yes, for sure. That's the way you set it up in this case. But this may explain your problems with the colours? Most of the images of the Veil are duoband / bicolour images, maybe with some RGB stars. But of course, in that way it is easy to get strong red / mint colouring. So you probably have a problem with your RGB / broadband stack (this seems to fit to the things you described in your next post).

I had a stack of pure Ha too

So taken with your mono DSLR and a Ha filter?
I suspect your unmodded broadband DSLR has a simply too weak response for the Ha line. My EOS was nearly blind for Ha until I modded it. This might explain your problems getting a decent colouring out of your broadband data.

I know this is a difficult target, but still wanted to do anyhow...because i find it so beautifull..

Yes, of course!

this is a plain OSC , no filter , no nothing....

I have colored stars, that seems all allright....but...not trace of red nor magenta on the Ghost...how weird...

I noticed in processing that only the outerlines of that object turned red if i oversaturate. You can see this on Stefans image too..the red is more in the outer parts of that nebulae. You see it better of course cause it is a astro cam, i believe.

Yes, no red because your OSC / unmodded cam does not capture the Ha line? But I'm not sure, why there's so little mint colouring. But this explains your problems regarding the colouring if you use this broadband data for colouring your images ...
(And yes, Stefan uses an astro cam or previously a modded DSLR and therefore has a stronger red signal.)

Best regards, Dietmar.

[decay]

Oops, I just have seen that Stefan already answered . Sorry.

[fmeireso]

First of all , i want to thank everyone for the positive feedback here

the stacks should one be interest to give it a go. Fits files , aligned


Mono stacks
https://www.dropbox.com/s/w2rz102zs4ehd ... r.fit?dl=0
OSC Stack
https://www.dropbox.com/s/8n85ryvnduji3 ... B.fit?dl=0

[fmeireso]

yes, no red because your OSC / unmodded cam does not capture the Ha line? But I'm not sure, why there's so little mint colourin

I don't really agree, because, in the OSC version, the ghost is quite visible, so signal is detected. If this is supposedly ha, why is the coloring not red then. I would understand , that if the signal was too weak and the OSC could not capture any red ha signal, no Ghost nor color would be there...I assume.

On some images on the internet the red is not always that prominent either
https://www.bing.com/images/search?view ... ajaxserp=0

Some even go to the purple or gray/blue. indeed others show much more red. The witchcraf nebulae , a reflection nebulae is often shown in thesame colors...; let's call that haloween colors

As far as I know the object barely contains any OIII at all so it might be worth a try to use all the slots in Compose by entering the OSC data into RGB and the mono data into luminance and NBAccent

I did use the mono in the luminance slot and the OSC in all the R-G-B slots. The result was the third image. Afaik you cannot use the luminance slot at the same time as the NBaccent slot, it is either the one or the other, unless i misunderstood the explanation in the PDF documentation.

[Stefan B]

Hi Freddy,

I had a quick look at your stacks and I guess you will really have a hard time coloring your luminance with the RGB data. As you've already noted IC59 and IC63 have blue reflection stuff in the "core" and red Ha on the periphery. And your luminance picked up the Ha but rather not the reflection nebula while your OSC did the other way round. You can see it here:

Ghost-Lum-vs-Color-small.gif (738.15 KiB) Viewed 3384 times

Your luminance and color data sets don't have much signal overlap and don't match in my eyes. It's almost as you'd try to color radio data with visual spectrum data when there nothing to *see* in the direction of the radio source.

It would be much easier if your OSC would be modded or if you used your mono with RGB filters for visual spectrum, too. At least that's my take on it.

Regards
Stefan

[fmeireso]

Thanks for analyzing , Stefan...

Hmm...so lacking Ha color...the only thing i can do for the moment is perhaps doubling the integration time on the OSC and hoping to cath some more Ha for the color then .... I don't have R G B filters and as far as i know the Elf does not use them either for his imaging. He uses the same camera's. I might PM him via CN, he has far more technical knowledge that i have ...

[Mike in Rancho]

Nicely done, Stefan!

Usually it's the intensity difference and the effect on color that's noted when using an alternate luminance, but occasionally for Compose we've noted the effect of detail difference.

Very starkly shown by your graphic here. They just won't match up well.

I also looked up the target on Stellarium -- seems quite low surface brightness. This would not be easy.

[Stefan B]

Hmm...so lacking Ha color...the only thing i can do for the moment is perhaps doubling the integration time on the OSC and hoping to cath some more Ha for the color then .... I don't have R G B filters and as far as i know the Elf does not use them either for his imaging. He uses the same camera's. I might PM him via CN, he has far more technical knowledge that i have ...

Your non modded OSC is certainly not completely blind to Ha but maybe just not sensitive enough to get a reasonable signal of such a dim target. Another way round may be to get Ha data (if I understood correctly you have a dedicated filter) with the mono and try l-eNhance mono data as luminance, broadband OSC data as RGB and Ha mono data for NBAccent. Maybe try not only L,RGB but L + synth L. Thus you get the rather small stars from l-eNhance (with a bit of synth L contribution of broadband), the details and color from the reflection nebula (which is lacking in your luminance data) and the NBAccent color matching your l-eNhance luminance.

Certainly sounds like a hell of a project

Regards
Stefan