IC 4628 Prawn Nebula under a Full Moon

[Startrek (Martin)]

Captured IC 4628 Prawn Nebula for only the second time, under a full moon last night using my L Extreme Multiband filter
Beautiful clear night , no wind , no dew but it was like daylight outside with that big full moon overhead

NexDome Obs
8” f5 GSO newt
Skywatcher EQ6-R pro mount
ZWOASI2600MC set in Ascom to highest dynamic range Gain 0 cooled to -10C
Optolong L Extreme OSC multiband filter
65 x 3 minute dithered guided subs
Goto and tracking EQMOD and Ascom Stellarium
Captured in APT
PHD2 Multistar guiding ( 0.80 arc sec error total )
Subs reviewed in Astap
Stacked in DSS
Processed in Startools V1.7 OSC Linear data set

Synthetic Luminance version
Compose Synth L , R ( 2xG ) B OSC version

Comments Welcome
Thanks

[Andy01 (Andy)]

Nice framing & composition Martin!
The dark rings around he stars in the colour version are distracting, maybe worth finding the cause?

B&W version looks pretty good!

[Startrek (Martin)]

Thanks Andy
Appreciate your comments
Yes the Luminance version does give some full depth and detail of the Prawn
In the colour version I created a star mask so as not to include the stars during processing the main objects colour It’s a bad habit of mine as you don’t need too , Startools takes that into account and masks the majority of stars down to a few pixels ( only the teeny weeny faint stars get caught up the colour saturation )
Only when doing OSC Bi colour in Compose you have to mask your stars otherwise they end up with all sorts of unusual colours.
Unfortunately Star Masks do leave a few pixels of background around the perimeter.Some of it does get hidden after Noise Reduction ( in the form of smear )
I must admit though OSC narrowband under a full moon with the fainter nebulas like the Prawn is difficult to process your colour or even extract a suitable bi colour version
Ive had more success with the likes of M8 , M16 , M17 and a few others
Cheers
Martin

[strongmanmike (Michael)]

Nice one Martin..how good are calm, clear dewless nights??

There looks to be some vignetting?..did you use flats?

Mike

[Andy01 (Andy)]

Originally Posted by Startrek

Thanks Andy

In the colour version I created a star mask so as not to include the stars during processing the main objects colour ...
Unfortunately Star Masks do leave a few pixels of background around the perimeter. Some of it does get hidden after Noise Reduction ( in the form of smear )

I used to use Startools, from memory one of the processes - Decon maybe? created dark rings around stars if the setting was too high.

[Startrek (Martin)]

Originally Posted by strongmanmike

Nice one Martin..how good are calm, clear dewless nights??

There looks to be some vignetting?..did you use flats?

Mike

Mike
Thanks for your comments
No I didn’t use flats
I’ve tried various methods to produce good flats at various ADU with my 2600MC , white T Shirt , LED photographic light panel with variable illumination settings etc.. and the various flats I produced don’t really help much with dust donuts and vignetting. A lot of folk with the 2600MC have similar issues obtaining good flats that work.
So I resort to keeping my sensor spotless and use the Vignetting preset in the Gradient Wipe module of Startools
Mistakenly with this image I forgot to use the Vignetting preset and used the Narrowband preset in Wipe ( Vignetting caused by full moon glare )
So to clean up the residual or trace of Vignetting in the image , I reprocessed the image using the Vignetting preset in Wipe
Here it is
Cheers
Martin

[Startrek (Martin)]

Originally Posted by Andy01

I used to use Startools, from memory one of the processes - Decon maybe? created dark rings around stars if the setting was too high.

Andy
I didn’t use Decon in Startools, I’m sure it’s the L Extreme filter creating this thin halo ring
It doesn’t appear as prominent on other images without the filter
Decon has come a long way in Startools to arrest the ringing around stars etc..

Cheers
Martin