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Problems with integrating Ha/OIII to RGB

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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi,

I know there are several threads with maybe similar problem, but they didn't helped me with my problem. I also tried the procedure as stated in this thread:

https://www.astropixelprocessor.com/community/tutorials-workflows/combining-r-g-b-with-ha-oiii-data-using-an-optolong-l-enhance-filter/

but also very unsophisticated result.

But from the beginning: I had two sessions with M16, one without an one with l-eXtreme filter. The results fpor each session looked very promising for my skills 😉 So I wanted to combine the pictures an dused the "combineRGB" in TAB "TOOLS".I splitted the RGB into the channels and splittet Ha and OIII in with the subsequent "algorithm" in TAB "RAW/FITS". These 5 pictures I registered and normalized.

To get the combined picture I used the formula RGBHOO and after getting negative results I added the Ha into RED and OIII into GREEN/BLUE as written in the thread mentioned above.: same result...

 

Here are the results (got with the "combineRGB"-tool, using same stretch and no saturation everytime):

Ha/OIII only:

M16 Ha+OIII

 R/G/B only:

M16 R+G+B

Ha/OIII+R+G+B with RGBHOO:

M16 Ha+OIII+R+G+B

What am I doing wrong? As I wrote before I tried the procedure described in the thread with the factor (e.g. 2.5 for the RED channel) but the result looks quite the same as RGBHOO. I also tried to play with the factors of Ha and OIII. To get an image which shows reasonable colors I have to reduce the factor of both Ha and OIII down to 0.1, which leads to a result looking nearly the same as RGB only... If I look at the RGB only and Ha/OIII only pictures it should be better???


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

That looks very strange indeed, how do the frames look like just before you use them in RGBCombine? So, the individual stacks for R, G, B and narrowband?


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi Vincent,

thank you for your reply. Would it make sense to upload the 5 files?

The frames look quite normal, and if I combine just Ha/OIII OR R/G/B then the combined pictures look also quite normal (as you can see in the first two pictures in my first post).

I also tried it in APP 1.083.2, but its just the same outcome.

 

Best regards

 

 

Juergen


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Hi Juergen,

Sorry for the delay, been very busy. Yes, you can upload the 5 frames first, just to see what happens here and if I can't see what's going on, I'll likely ask for more data. 🙂


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi Vincent,

no problem, I think you are quite busy with V2.0.0...

Since I was just in front of my PC I already uploaded the files. I think the file names are self explaining. Ha and OIII was done with l-eXtreme, R,G and B with Astronomik L-2 filter, both with my QHY 268C.

 

Thank you for your support 🙂

 

Best regards

 

Juergen


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Ok, having a look now. I notice that the RGB itself seems to combine fine, but as soon as I add narrowband data, something is up. I suspect a data issue here, when I load in the OIII by itself just to check, it looks like this:

image

How did you take this data and how did you load it from the telescope to the computer and into APP? This kind of interference seems a bit like a data transfer issue perhaps. Or are you processing on an external harddrive?

Would be nice if you could upload like 10 subs of the OIII and Ha, together with the darks, bias/flat darks, etc.


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi Vincent,

strange! I dont see these stripes in my OIII fits which I sent to you (and also not for the Ha). If I only open this file it looks like that:

M16 OIII

 

I will upload some subs of my l-extreme narrowband and the master dark/flat/darkflat.

 

At the moment I upload the files. Since I had two sessions (with the same flats) I upload ten files from each session (named M16_S1... and M16_S2...)

 

Best regards

 

 

Jürgen

 

P.S.: as always I took the pictures with kstars on Raspi 4, the pictures are saved localy on the raspi, after the session I download them to the PC. All other process is with APP


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

You maybe can notice the pattern in the OIII file when zooming in or out, if I zoom in a lot it's less clear, but you can see differences in the background noise that end up causing these patterns. You don't see that at all? Thanks for uploading! edit: I'm also wondering if the bands can be some conversion issue btw, as APP does convert the values a bit, never seen anyone mention that though, but I'll keep that in mind and inform Mabula if that might be the case.

image

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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

yes, if I zoom in I also see those lines in the separated fits data. i dont see them in the stacked picture befor separating OIII and Ha. Perhaps the separation creates those artefacts? I used drizzle-mode (Bayer- / X-trans) when creating these separated files.

 

What I dont see are the big stripes you shown in your picture in your post from 10:31.

 

But despite that artefacts for me it is not clear why I get those crazy colors in trhe RGBCombine. i' curious what you will find out.


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Yes, I will investigate that further with your new data as well, but it does point to an issue in the narrowband data, the bands are just an indication something is up. 😉


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Just an extra verification; I assume you did use the "extract-Ha" and "extract-OIII" algoritms?


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

yes thats right


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Hi Juergen,

Could you indicate which ones are taken with Ha and OIII, S1 and S2?


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

I think I figured it out based on the signal. 😉 When I add a masterdark to the Ha frames (S2), I see this message in the console:

1227 - GENERAL IMAGE LOADER: loading frame D:\Moderator\juergenn-RGBCombine\MD-IG_60.0-E300.0s-QHY_CCD_QHY268C-9ee77c4-6252x4176-all_channels-session_1.fits
1228 - 2) CALIBRATE: performing calibration in 32bits normalized floats...
1228 - 2) CALIBRATE: converting data to 32bits normalized floats...
1228 - GENERAL IMAGE LOADER: frame D:\Moderator\juergenn-RGBCombine\MD-IG_60.0-E300.0s-QHY_CCD_QHY268C-9ee77c4-6252x4176-all_channels-session_1.fits was loaded successfully
1228 - 2) CALIBRATE: Adaptive Data Pedestal : raised to: 4.768E-02
1228 - 2) CALIBRATE: Adaptive Data Pedestal : because 2937 pixels are clipping to 0 without it!!!

Which can indicate that either the frames were not exposed long enough to get well above the background, or that the signal in the darks is too high due to an issue there (going to check that). The OIII (S1) signal is even lower, so that will for sure cause issues and I think this is at the basis of the problem you get when combining signals.


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi Vincent,

both S1 and S2 are taken with the l-extreme (Ha and OIII). So you can extract Ha and OIII from all 20 files.

 

Regarding Darks: Maybe the dark datas are too old? I took them last October. Perhaps it would be better not to use Darks in that case?

 


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Ahh, sorry I should've seen you used that filter for both. Ok now that is interesting, I do see a difference between S1 and S2 in terms of overall signal, so maybe it has to do with conditions during the nights? You can indeed try to make new darks and maybe expose for longer with that filter. Not using darks in this case may be a good idea, you can also just use the BPM instead of the darks (if you don't have amp-glow, which I think is the case).


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

S2 was done the night after S1, all the equipment stayed in the observatory. At least moon was different, but all the other things (should) be the same.

 

Normally I expose 900s with the l-extreme, this time I tried 300s to reduce overexposed stars in the pictures.

 

Yes, the QHY268C has no amp glow


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

I think that may explain it then, the clipping of pixels isn't a big issue, so a bit longer of an exposure and new darks might solve your issue. I would try this data without any calibration first and then just add the flats etc to see when the issue starts popping up.


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(@juergenn)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 37
Topic starter  

Hi Vincent,

just an update from my side: yesterday night I took pictures of the veil nebula with l-eXtreme. Again I tried to combine Ha and OIII. I extracted like before Ha and OIII WITH drizzling. Result was a red picture. If I turned down all the sliders for the Ha part of the picture I got a weired colored result.

So I tried extracting Ha and OIII WITHOUT drizzling and combined these Ha and OIII. Result: Pretty picture with nice colors and the possibility to tune the amount of each color.

So in my opinion the weired things here have to do with drizzling. My intention to use drizzling was, to get a little bit more resolution. But now I see, that I have to do it without drizzling...

 

Best regards

 

 

Jürgen


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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5229
 

Hi Jürgen,

Interesting! That should also be possible, I've asked Mabula to have a look as well here. Please allow for a day or two as he's also quite busy. 😉


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