Crab Nebula HOO questions

[Mike in Rancho]

Hi Jeff,

I took a quick look at things. Actually found some banding in the data, which I tried to get handled in Wipe with the adaptive horizontal bias. Seemed to help, but maybe I could have done more.

Then, setting aside the red/blue balance, I changed a few things up from normal to go for a softer stretch with my ROI, and squashing shadow range in OptiDev and Contrast. Your APP version, which you seemed to like, also had a more limited stretch so I tried to head in that direction. I could also predict from the other edits that there could be potential trouble with blown-out or near-blown-out white regions. ?

I also kept HDR at defaults for further taming. SVD9 did not give me any viable starfishies, possibly a result of my weak stretch, so I was left with synthetic. If needed I might have used extended dynamic range here though too. That was too bad though, as I think SVD would have really helped clarify detail here.

Then just playing with the Color module for balance and saturation, followed by an SS-Isolate and denoise. I think a nice looking final would also result from a last step FilmDev to drop the gamma 10% (which would also help hide remnant banding) giving a bit more contrast - though I suppose I could have done that in SS too while I was there, but I like looking at that after denoise is finished. Also I had already smashed the shadows down so much, I didn't really want to remove even more faint detail than I already had.

Cool stuff! I didn't know this was in the ol' Orion neighborhood. Will have to try it out - though I'm a little short on reach with the scope I like using these days.

Jeff M1 bicolor ST9 1A.jpg (406.13 KiB) Viewed 19475 times

[jhart]

Hi Mike,

Thanks for the comments. I also noticed the banding. I tried using the Walking Angle Noise parameter in Tracking Off/Denoise in ST8 to remove it there. Is Wipe a better place to try to deal with that?
I am flummoxed by ST9 Decon. So far I can't get it to pick stars to sample in any data set and regardless of what I do in the preceding modules. It also does not appear to give you the option to try to create a different mask to put some of its starfish on some stars to sample.
I am a fan of APP for stacking and related things such as mosaics. It also gives you a good basic look at your stacking result automatically at the conclusion of its integration run. I would not say its post-stacking tools are comparable to ST. I referenced it in my initial post because I thought I might have a problem somewhere due to my surprising amount of OIII with the use of the new L-Ultimate filter and my initial foray in ST with such narrow band data.

Jeff

[Mike in Rancho]

Yeah Jeff, even with an L-Ultimate there's quite a bit of something coming through the OIII band, though I have no idea if it is true OIII.

Is this considered a PN, or SNR? Either way it makes sense as they are not quite so Ha dominant.

I didn't think about Walking Noise in Denoise for the banding, so I guess whatever works best. If it's minimized early, I suppose there's less chance of accidentally enhancing it with the other modules, but DN may be sufficient, along with perhaps just minding the stretch or squashing it down.

The SVD9 sampling will get worked out - preview revision right now and hit or miss.

[decay]

Cool stuff! I didn't know this was in the ol' Orion neighborhood. Will have to try it out - though I'm a little short on reach with the scope I like using these days.

Hi Mike, yes that's a fascinating object that I have wanted to shoot for quite a time. But be prepared to get a somewhat ridiculous result like this:

2022-12-20 20_32_36-Window.jpg (47.13 KiB) Viewed 19439 times

This target is a bit out of range for our Newtonians, I guess. Taken with 1m focal length, DSLR pixel size 3.72µm, bin 50%. So its really tiny Unless you have a scope like Jeff
First I took the full spectrum image on the left and I was pretty frustrated. And I was even more frustrated as I saw Jeff's awesome dataset here only one day later and so I decided to try a Hail Mary ( ) and did this second shooting with my Optolong L-enHace duoband filter in place. But I'm afraid, I do not feel any better now

But what I want to point out (also @Jeff): In visual spectrum this object appears to be almost white. I did colour balancing with star samples and therefore I guess, that colour balance shouldn't be too much off. And this fits with what I've read about M1: The pulsar in its centre emits synchrotron radiation at all wavelengths. And therefore a part of the captured 'OIII' is likely to be synchrotron radiation at that wavelength only.

Best regards, Dietmar.

[Mike in Rancho]

That's still pretty nice, Dietmar, even for a too-short 1000mm!

Interesting on the white light. Though whether you want to balance it to white in duoband is a matter of choice, I think. Even if not true OIII, the duoband is still only capturing that thin slice (of the continuum) which is teal. So such a bicolor (however balanced) will show areas of white where you have balanced a relatively even concentration of Ha and the "teal slice" of whatever that represents.

I think.

[jhart]

FYI,
My focal length for the Crab Nebula was 2654mm with the OAG and filter drawer. That is pushing the envelop on what is doable from my light polluted city neighborhood. (I like that APT tells you your exact focal length).

Jeff

[fmeireso]

AFAIK you don't need to extract the channels beforehand. ST will do that for you. Just load the same file into the RGB slots. Set parameter [Luminance, Color] to [L + Synthetic L From R(2xG)B, R(GB)(GB) (Bi-Color from OSC/DSLR)].
Later in Color Module set parameter [Matrix] for example to [HOO Duoband 100R,50G+50B,50G+50B]. Then try to use Bias sliders to set the desired colour balance between channels.

At least this is what I did with my duoband datasets. Good luck!

Best regards, Dietmar.

2022-12-17 18_56_25-Greenshot Editor.jpg

Hmmm, i did not know that either. I used to extract the red and the blue/green channel for doing HOO. So this is no more needed?

CS
Freddy

[decay]

I used to extract the red and the blue/green channel for doing HOO. So this is no more needed?

Yes Freddy, that works fine just like described. I read that in one of Ivo's posts (I did a search in past forum posts as preparation) as I started with duoband/HOO imaging last summer. Duoband/HOO imaging worked right from the start for me, without any problems. I never tried duoband imaging while my EOS 2000 was still unmodded, because it was clearly visible how weak sensitivity for deep red / Ha was. So I modded the camera and bought that L-enHace filter - in this order, because I was afraid to wreck the cam while modding. Great Scott, I sweated blood and water .

Best regards, Dietmar.

[fmeireso]

thanks Dietmar! i did not know...saves time for processing