NGC 253 Sculptor Galaxy 2nd Capture with 2600MM

[Startrek (Martin)]

There’s still quite a few galaxies positioned nicely in the east during the new moon so decided to experiment a bit more with broadband imaging under heavy light pollution using my 2600MM on NGC 253 Sculptor Galaxy.

Over a couple of nights captured 3 hours of Luminance and slightly more than hour each of Red , Green and Blue.

This time set the 2600MM to Gain 0 ( instead of Gain 100 )

Bortle 8 skies City Suburban
New Moon period
8” f5 Klaus Helmerich Carbon fibre Newt
Skywatcher EQ6-R pro mount
ZWO2600MM cooled to -10C , Gain 0
Antlia L RGB Pro series filters
ZWO 7x2” EFW
TS optics GPU coma corrector
Orion 60mm Guidescope with helical focuser
ZWO 120MM-S guide camera
190 x 60 sec Lum subs
75 x 60 sec Red subs
73 x 60 sec Green subs
75 x 60 sec Blue subs
Flats and Bias for all filters
EQMOD and Stellarium for Goto and tracking
APT capture software
PHD2 Multistar guiding ( 0.50 to 0.60 arc sec total rms )
Dithered every 2nd sub
Stacked using ASTAP
Processed in Startools V1.8 ( Data set loaded via Compose ) Luminance type L + Synthetic L , RGB , RGB

A couple of takeaways from this project -
The luminance data was way overexposed at 60 seconds under Bortle 8 skies. I tried processing with and without Luminance and found results were significantly better without it.
Moving forward , Luminance subs will have to be between 10sec and 30 sec maximum under these heavy light polluted skies. The 8” newt and the 2600MM with only a Lum filter just sucks in those photons and Skyglow ( not to mention neighbouring lights )
I processed just the R, G and B and Startools creates a Synthetic Luminance.
The image had less noise to deal with yet still had good detail.
Id wished I had 3 hours of additional RGB data rather than unusable Luminance data.
Switching from OSC to Mono is a big learning curve

Astrobin link below for full resolution…….

https://www.astrobin.com/izyu3e/

*** Also photo of initial auto stretch before gradient wipe , don’t you just love heavy light polluted skies !!

Comments welcome

Thanks for looking

Martin

[bluesilver (Peter)]

It is looking pretty good.
The new camera is working out quiet well for you.
The detail in the arms looks promising.
Well done.

[Startrek (Martin)]

Thanks Peter
The camera is working out well , it’s just the operator that needs to learn to harness its capabilities and performance under crappy skies
I tend to repro the same image a few times to squeeze a little more detail etc..
This time I Binned the image at 71% instead of 65% which allowed a slightly bigger crop and slightly more stretch to expose the core and the outside spirals
I also back off on colour saturation and adjusted the RGB balance to shift the purple / mauve colour to more of a blue.
The noise reduction at the end to smear the grain required 4 pixels instead of the previous version which required 3 pixels
Damn I wished I knew about the Luminance exposure issues , I could had added 3 hours of more RGB to this image which would have been a much better result.
Live and learn…..,

Here’s the repro …..

Cheers
Martin

[Dave882 (David)]

Nice one Martin I think you’re really getting the hang of the new camera and this has come out really nice. I reckon you may have been battling some poor seeing too as it’s been really bad in Sydney lately. Some better conditions may help to resolve some more detail in those inner dust lanes. Good call with the colour.

[strongmanmike (Michael)]

Your a trooper Martone, always having a go, love hearing about your imaging efforts as much as seeing the results

Mike

[Startrek (Martin)]

Originally Posted by Dave882

Nice one Martin I think you’re really getting the hang of the new camera and this has come out really nice. I reckon you may have been battling some poor seeing too as it’s been really bad in Sydney lately. Some better conditions may help to resolve some more detail in those inner dust lanes. Good call with the colour.

Thanks Dave,
The waisted 3 to 4 hours of Luminance was a real bummer. I don’t even know if it’s worth shooting 10 , 20 or 30 sec Lum subs as I’d need probably 500 to 1000 subs to achieve decent SNR. Really short subs are still noisy with some signal.Luminance is suppose to provide all your fine faint detail, but I certainly couldn’t see that after a stretch.
I’ve been reading a few Posts on CN and a lot of folk opt for capturing more RGB and using a Synthetic Luminance ( like I did on this image but unfortunately no where near enough RGB )
Seeing might have been poor but it didn’t reflect in my guiding , guiding was really tight , almost flat lining for my mount
I tried SV Decon in Startools to try and deblur the atmospheric effect but due to the massive noise reduction plus reduction in overall image size in pixels , this algorithm didn’t work that well, so I abandoned it ( it works a treat though for Narrowband or broadband in darker skies )

There’s no substitute for Dark Skies like down at my Dome !!

Cheers
Martin

[Startrek (Martin)]

Originally Posted by strongmanmike

Your a trooper Martone, always having a go, love hearing about your imaging efforts as much as seeing the results

Mike

Thanks Mike,
Yeh it’s a struggle in the big smoke , especially when your neighbours either side with 2 storey homes leave all their backyard, side passage and facade lights most of the night ( they must have a fear of the dark or something )
Imaging at both chalk and cheese locations ( Sydney and South Coast Dome ) certainly makes the hobby frustrating, challenging and rewarding.
Gee what did you long timers do 30 odd years ago under crappy skies with film gear. Must have been tough to get a decent image.
Hats off to the pioneers

Cheers
Martin