M20 Trifid Nebula from NexDome Obs

[Startrek]

I had some maintenance work to do at my bortle 3/4 dark site retirement retreat for 2 days so took the opportunity to image on the first night. Chose M20 Trifid nebula again so I could compare my recent M20 captured under City suburban Bortle 7/8.

New moon
Bortle 3/4
Conditions were poor to average
NexDome Obs
10” f5 Klaus Helmerich Carbon fibre Newtonian ( built by me )
ZWO2600MC cooled to -10C , Gain 101
No filters , just internal UV/ IT cut protective window
138 x 60 sec subs , dithered every 2nd
40 x Flats
60 x Bias
EQMOD and Ascom Stellarium
APT
PHD2 Multistar guiding ( 0.75 to 1.0 arc sec , poor guiding , chasing the seeing )
Stacked in DSS
Processed in Startools V1.8 OSC linear data set

Astrobin link below ….,

https://www.astrobin.com/8fs7m9/

Attached Synthetic Luminance version
Original Native frame
Crop frame
I sometimes like to present synthetic luminance images as it does expose some finer details where colour versions seem to mask some of the fine detail due to colour saturation etc….

Obviously this M20 image was so much cleaner than the City suburban Bortle 7/8 M20. The resultant noise was so minor that I could have skipped noise reduction all together
Imaging from both ends of the Sky spectrum ( Bortle 7/8 to Bortle 3/4 ) does make you appreciate the fact you can image under fairly dark skies which provides so much more capability in post processing

Comments welcome
Thanks
Martin

[Startrek]

Forgot to attach photos of my laptop screen during capture plan under both Bortle 7/8 City suburban skies and Bortle 3/4 dark skies at my NexDome Obs

Bortle 7/8 City suburban skies New 8” f5 Klaus Helmerich Carbon fibre Newtonian
Bortle 3/4 Dark site NexDome Obs 10” f5 Klaus Helmerich Carbon Fibre Newton ( 12 months old now )

And this is during the new moon period

Pretty easy to guess which ones which ?

Clear Skies
Martin

[decay]

Hi Martin,

thanks for sharing the photos of your laptop screen under Bortle 7/8 and 3/4 skies. I think I've never seen such dark skies. That's great, lucky you I'm still wondering about the quality of the sky here at my location. It's probably a bit better than your suburbian sky, maybe Bortle 6 I guess.

Best regards, Dietmar.

[Mike in Rancho]

Well, I don't know APT. All the green is light pollution?

I otherwise would not be able to tell. The scales are quite different also so hard to match. I could go look at your other recent images and double check which Newt has the longer focal length maybe. Both seem to look awfully good.

[Startrek]

Well, I don't know APT. All the green is light pollution?

I otherwise would not be able to tell. The scales are quite different also so hard to match. I could go look at your other recent images and double check which Newt has the longer focal length maybe. Both seem to look awfully good.

Mike,
The green cast is definitely light pollution
Same camera , same Gain , same exposure lengths , same cooling, same Laptop and only a small difference in focal length
I also initially tested my 10” at my city suburban location , green cast as well

Martin

[Startrek]

Well, I don't know APT. All the green is light pollution?

I otherwise would not be able to tell. The scales are quite different also so hard to match. I could go look at your other recent images and double check which Newt has the longer focal length maybe. Both seem to look awfully good.

Mike,
The green cast is definitely light pollution
Same camera , same Gain , same exposure lengths , same cooling, same Laptop and only a small difference in focal length
I also initially tested my 10” at my city suburban location , green cast as well

At my Bortle 7/8 City suburban location you look up and can only see a handful of bright stars, sky looks dark grey not black
At my Bortle 3/4 dark site you look up and see billions of stars and the Mily Way plastered across the night sky in a huge arc or band under black skies
Chalk and cheese really

Martin

[Mike in Rancho]

Mike,
The green cast is definitely light pollution
Same camera , same Gain , same exposure lengths , same cooling, same Laptop and only a small difference in focal length
I also initially tested my 10” at my city suburban location , green cast as well

Martin

Thanks for the explanation, I think I get it now. Both screens are showing a debayered preview, and the (expected) green bias is picking up and showing a huge overall brightnes cast across the screen. Boy, so much!

I have driven across the far desert plenty of times at night, although it's been many year now, and been able to see the MW from B2 or whatever it might be. Though I never stopped to stargaze, nor have I been out there for any imaging. Must make for amazing data.

Scales are still too dissimilar to me to be able to see how the processed differences turn out though.