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The Lagoon Nebula - Narrowband vs Broadband

astrophotography CMOS refractor
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#1 Camissa



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Posted 22 August 2019 - 05:04 PM

M08 Forum D.jpg

Lagoon Nebula (M8) narrowband


I imaged the Lagoon Nebula just 2 weeks ago with the ASI294 MC Pro. I was not really happy with the result and it was time for first light with my new ASI1600 MM Pro monochrome camera and my first attempt at narrowband imaging. 


I was a bit confused how to process the data but some friends confirmed to treat each channel like a separate image (calibration, registration, integration). The resulting masters were processed with Dynamic Background Extraction and Multiscale Linear Transform. I then registered the 3 linear masters with each other and used simple Pixelmath to make an RGB. This was slightly processed (Dynamic Crop, Histogramm Stretch, Curves, Morphological Transformation (to decrease star sizes and to eliminate the tiny stars), and finally a little Unsharp-Masking to make the stars pop a bit.


Unfortunately, clouds came while S-II data was acquired so I had to shut down with S-II only 30% done. I will collect some more data and will then reprocess everything.


However, I am quite happy with this first result. I have included a link to the Astrobin higher resolution image and also a link to the OSC image from two weeks ago. Note that besides broadband vs. narrowband the images were taken with the same telescope and the same total data acquisition time from the same suburban location. Seeing was better during the narrowband imaging. Both images suffer from my lack of skills and experience in imaging and processing though. 






150 secs per subframe, 16 H-a, 16 O-III, 5 SI-II, ASI 1600 MM Pro with Astrodon 5nm filters. 





35 secs per subframe, 158 subframes, gain 117, ASI 294 MC Pro.



Everything was guided with PHD2, imaged with Sharpcap, and processed with Pixinsight and Apple Photos.


Any tips for improvement or comments are highly appreciated. Thanks for looking.


Clear skies,


Edited by Camissa, 22 August 2019 - 05:33 PM.

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#2 descott12


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Posted 22 August 2019 - 05:50 PM

Actually, I think the OSC image is way better.  Probably just due to the learning curve with NB but it looks great to me.

#3 stargazer60


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Posted 22 August 2019 - 05:56 PM

I have to agree with descott12 the OSC image very good, but as you work with narrowband it too will come.  Keep up the great work.

#4 Camissa



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Posted 23 August 2019 - 06:44 PM

Interesting! I thought the narrowband image was better. I acquired some S-II data tonight and will try to reprocess. Maybe I can make use of some of the OSC data too. 

#5 ciraxis


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Posted 24 August 2019 - 08:05 PM

Lagoon is an object that I prefer in LRGB or HaLRGB, I don't care for it in strictly narrowband.  

#6 Marco 104

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Posted 25 August 2019 - 04:17 PM

I'm in the process of deciding which camera to get, 294 or 1600, the first would allow to achieve great results in shorter time, the second permits to exploit narrowband, while still keeping the possibility to go for RGB


For Lagoon I also prefer the RGB/OSC version, did you acquire any data in LRGB with the 1600? This would be an interesting comparison, keeping optics and sky the same 



#7 JamesTX


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Posted 27 August 2019 - 01:12 PM

I'll buck the trend here a little and say I like the NB image more, nice and clean.. although its too orange. 


Try using the lrgb tool. Leave L unchecked.  Assign s2 to red, Ha to green, and O3 to blue.  Then hit it with ABE/DBE.  After that, if there is still too much green/green noise.. use the SCNR tool to take care of that.  After you are nearly done processing it.. if your star color is funny looking (purplish) Hit ctrl-i to invert your image.. use the SCNR tool to remove green again, then ctrl-i to invert back.  Star color should look better now.

#8 dhaval



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Posted 27 August 2019 - 02:02 PM

I like the NB version better - I believe the underlying data seems to be a lot better than the OSC data. The issue with your NB image is not the actual data, but rather its processing. I think you're clipping the background a bit and you need to do a better job with the color palette. Once you have those two sorted out, it should look much nicer.


To me, the OSC image looks a bit noisy, that is a data issue. Data issues are very difficult to fix in post processing unless you jump through hoops using something like PixInsight. 



#9 MikeMiller


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Posted 27 August 2019 - 06:12 PM

I've done HaRGB on this and have liked the result.

#10 Camissa



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Posted 30 August 2019 - 02:10 AM

M08 Forum D Hubble.jpeg


Thank you for your comments. Yes, I also think the OSC image has more noise. I captured more data and reprocessed the Lagoon - every image shows my own progress in learning AP and Pixinsight in particular.


I will do an LRGB version when weather permits - this comparison of different imaging techniques with the same gear and sky is very informative for me.


High Res Link:




Clear Skies,


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