Omega Nebula (M17) and Processing Tips

This is my second attempt this season at capturing and processing the Omega Nebula. This time I managed to capture 8 hours of narrowband data across four nights - lucky we finally had a good run of clear skies. I processed the data by putting Ha in Red and OIII in Green and Blue. In this video I also discuss how to combine the different filters and cut through the brightness of the nebula with PixInsight Here is more info on the hardware and software:
Target:
Omega Nebula (M17)
Imaging Telescope:
Explore Scientific 127mm ED Refractor (952 focal length)
Focuser:
MoonLite 2.5" Focuser with Motor Auto-Focus
Field Flattener:
HoTech 2" SCA Field Flattener
Mount:
Celestron CGX
Polar Alignment:
QHYCCD PoleMaster
Imaging Camera:
ZWO ASI1600MM-Cool
Frames:
Frames:
Astronomik Ha: 60x240"
Astronomik OIII: 60x240"
Integration: 8 hours
Ha: Gain=139, Offset=21
OIII: Gain=75, Offset=15
Guide scope:
Orion ST80
Guide Camera:
Lodestar X2
Guide Software:
PHD2
Calibration Frames:
Darks: 50, Bias: 50, Flats: 50
Capture software:
Sequence Generator Pro (SGP)
Stacking software:
PixInsight
Post Processing:
PixInsight, PhotoShop
Dew Shield, Dew Heater Strip
Astrobin: astrob.in/355891/B/

[@DennisCarmody]

Always enjoy your more thorough walk throughs! Keep up the great image work and clear skies!

[@ChucksAstrophotography]

Thanks Dennis

[@jimdrever9936]

Thanks for this video Chuck....I always learn something new.
Oh, and beautiful shot too!

[@ChucksAstrophotography]

Thanks Jim.

[@RaysAstrophotography]

Good Job Chuck. Great tips.

[@ChucksAstrophotography]

Thanks Ray

[@AdvancedHalo]

Really nice Chuck!

[@ChucksAstrophotography]

Thanks AdvancedHalo

[@N4GW]

Looks great

[@tommyboypackham9668]

Your latest looks pretty awesome! I am using DSLR and lens at the moment but hope to go tele and CDD/CMOS soon. Will go Narowband also mostly as live in fairly light polluted area. Watching your videos and workflow is great 👍 Your final results always make me 😮

[@ChucksAstrophotography]

Thanks TommyBoy, good luck when you get your CMOS camera - you'll love it.

[@alexevivi]

Beautiful.

[@ChucksAstrophotography]

Thanks Alex

[@eddwar8597]

Great picture.

[@ChucksAstrophotography]

Thanks EddWar

[@M31glow]

I like the one on the right more, the yellow tones are perfect

[@ChucksAstrophotography]

Thanks Walter, I liked the yellow too.

[@astrophotonics9470]

To me its right on the Money, Good work.

[@ChucksAstrophotography]

Thanks John

[@davepastern]

Lovely image Chuck. Have you thought of posting on the PixInsight forums about creating a L layer with pixel math?

[@rtpman1953]

Thanks for the video and the very nice image. You've inspired me to spend more time in curves transformation to bring out the other subtle colors. I wonder on the bright core of the nebula if changing the kernal radius of LHE might have brought out more detail. Not saying it would but may have. I've been experimenting with two passes of LHE. One at the small kernal radius and second at larger kernal radius. Sometimes it helps it. Yes, the newer image is my pick as well.

[@ChucksAstrophotography]

Thanks Paul. Actually, right after I made the video, I did play around with the LHE settings and grabbed more detail in the core area. The final result is on Astrobin.

[@kajouman]

good video chuck...it helpt when using pixinsight

[@ChucksAstrophotography]

Thanks kajouman

[@Max6785]

Hey Chuck, excellent vid as always. I'm curious about something you said early in the vid about your guiding of .8 for low south. I noticed my own guiding on the trifid the other night was pretty bad (1.2ish) which is also low south. Why is that region such a problem for guiding?

[@ChucksAstrophotography]

Maybe because they are moving faster across a different arc because of their position?

[@thesammyjenkinsexperience4996]

At a guess, I'd say your star size and saturation issue with the OIII filter is caused by shooting through more atmospheric haze and light pollution. If it's only happening with objects in the southern skies it's probably because those objects are always in that thicker band of haze, whereas northern objects are going to pass through the thinnest part directly overhead and during integration those images will outweigh the ones closer to the horizon. What's the bandwidth of your Astronomik filters? They're 6nm or 12nm, yeah? You might want to try Astrodon 3nm instead.

[@thesammyjenkinsexperience4996]

I had this really weird problem with this one star in my Carina nebula mosaic. In 36 panels (12 in each narrowband wavelength) there was just this one star that came out huge in Ha, but small in OIII and SII. I had captured that same region twice over a month apart too, same thing. I did the mosaic with the Hubble palette and there's this massive green star in there. It looks kinda ridiculous but i kept it anyway.

[@ChucksAstrophotography]

All of my narrowband filters are 6nm. This was my last low object for a while.

[@thesammyjenkinsexperience4996]

Do you use the Local Normalization tool immediately before integration in Pixinsight? I ask this because you mentioned being concerned about subs with plane and satellite trails. These really shouldn't be a concern to you at all if you use Local Normalization with outlier rejection enabled. Using the output from this tool during image integration should remove planes, satellites, powerlines, etc.
I also use the Subframe Selector script to assess which are the best images using a third party algorithm and then insert a weighting keyword which is also used during image integration to prioritize cleaner images. If find the combination of the two tools eliminates all unwanted junk.

[@ChucksAstrophotography]

Thanks, but the planes I am talking about are huge, low flying and go across the whole frame - there is no way of saving it, not thin lines - but very thick.

[@hurriyetpek77]

in your opinion Chuck.. is it really a big difference between a 80mm triplet and a 127mm one.. just got an 80mm edt cf triplet apo.

[@ChucksAstrophotography]

Well me 127mm has twice the focal length as my 80mm, so the 127mm will always be able to grab more detail than the smaller scope. But of course the 80mm has a nice wide field of view. So I think there is a big difference, but I feel the scopes compliment each other - I'm glad I have both.

[@hurriyetpek77]

i c thank you. you deliver a lot of information regarding ap 'n processing.. much appreciated.. allways enjoy your vids

[@thesammyjenkinsexperience4996]

You've listed in your specs that you were at gain 139 offset 21 for your Ha images but your sample mean readout is the same as a bias frame (at least in my 1600) for that setting. Are you sure it wasn't gain 75?

[@thesammyjenkinsexperience4996]

Hrm, weird. I just took a few bias subs at gain 139 offset 21 and the mean readout is around 300. It was about 760 for me a few weeks ago.

[@ChucksAstrophotography]

Oops, I just checked - my mean readout for Bias is 300. 218 for gain 75. I must have given you the wrong value when we discussed this before.

[@thesammyjenkinsexperience4996]

Chuck's Astrophotography No, you gave me the right value before. I don't think I had my gain setting at the right value when I took my bias frames. I thought I took them at 139 but it must have actually been 200.

[@ChucksAstrophotography]

Oh ok. I have so many things going on, I can't keep track.

[@thesammyjenkinsexperience4996]

Chuck's Astrophotography It's cool. My values were 76/209, 139/300 and 200/760. I've been spending the last few nights trying to find optimal exposure times for 76 and 200 using the background mean readout. I try to sit at around 350-450 above the bias mean readout.