NGC 1365 Galaxy from B8 Sydney Skies

[Startrek]

Here’s my humble little image of NGC 1365 Great Barred Spiral Galaxy from B8 heavy light polluted Sydney Skies over the past week or so.
Captured over 3 half nights with a 25% waxing moon on the last night until late.
Same deal…,
8” f5 Klaus Helmerich Carbon Newt
Skywatcher EQ6-R pro mount
ZWO 2600MM Cooled to -10C , Gain 0
PHD2 Multistar guiding ( 0.50 to 0.65 arc sec )
EQMOD and Stellarium for Goto and tracking
APT for acquisition
Lum 510 x 30sec subs
Red 250 x 30sec subs
Green 250 x 30sec subs
Blue 240 x 30sec subs
Dithered every 3rd sub
Full calibration suite
Darks
Flats LRGB
Flat Darks LRGB
Total integration approx 10 hours
1250 x 30 sec subs !!!
Analysed , Calibrated and Stacked in ASTAP
Processed in Startools v1.8

Definitely not enough data to peg back the noise and expose more signal ( detail) I reckon 30 to 40 hours and we’re talking about some decent SNR (We just don’t get enough clear moonless nights in Sydney over 2 or 3 cycles, plus I have a limited view of the sky )
I had to turn down the gamma or background brightness to hide the gradient bomb. The signal is there but so is the noise.
At my B3 dark site down south I can push 180 sec Luminance subs and the background value of each sub is around 600 to 650 . In Sydney a 30 sec Luminance sub has a background value of around 1100 to 1200. Chalk and cheese.
I cropped the image so it wasn’t a tiny dot in the frame.
Anyway whinge over ……,

Thanks for looking

Comments welcome

Martin

[strongmanmike]

Perfectly ok to whinge, we stand in solidarity with you :gday:

Well done on capturing a worthwhile image, sometimes the fishing trip yields less than an ideal catch but the trip was still fun :thumbsup: :fishing:

Mike

[Startrek]

Thanks Mike,
Yeh definitely worth a go , at least you can see the little sucker past all the snowstorm.
I think I’ll leave these dim ones for down south , where results would be significantly better.
Cheers
Martone

[Dave882]

Martin that's a more than respectable contribution! The overall structure is well resolved, and it's just the fine detail and those dimmer regions that is effected by the lp noise. But yes, without consecutive clear nights over a new moon you can't hope for much better from the suburbs. The last month or 2 has been really dismal, and even when the sky clears its only for a few hours, and the jet stream...yeah don't get me started....

I've resolved to the fact that unless I can capture around 30hrs from my location it'll be a bit sub-par...but then again, you can only work with what you've got!

Keep up the great work mate!

[TrevorW]

Nice effort Martin I can sympathize with you re light polluted suburban skies :)

[Startrek]

Thanks Dave,
Appreciate your positive feedback
I guess I’m forgetting that I’m imaging a mag 10 dim Galaxy with an angular size of 11 x 6 arc mins under B8 skies with neighbours backyard floodlights on until midnight and only a 8” aperture at 1000mm focal length. Then throw atmosphere seeing into the equation plus Sydney’s central CBD light dome to the North causing a huge bias in the gradient snowstorm , so it ain’t too bad for only 10 hours I suppose.
I imaged M20 Trifid in LRGBHa during a new moon winter with 30 sec subs ( 8 hrs of LRGB and 2hrs of Ha ) and the gradient was manageable and easy to mitigate. The image turned out to be one of my best M20’s in years. Admittedly M20 is a mag 6 object with a dense Star field and loads of Ha so a huge difference in size and brightness from that of tiny dim NGC1365.
These ZWO 2600 series cameras are so damn sensitive , they gobble up photons but also LP gradients as well.
Still thinking about that Antlia Triband LRGB broadband filter as a substitute for Luminance ( only for use in Sydney of course)
Thanks again
Cheers
Martin

[Startrek]

Thanks Trev
Yeh I do carry on a bit but it ain’t easy in one of the most light polluted Cities in the southern hemisphere.
Lately I haven’t had time to get away down to my Dome and B3 skies due to Grandparents duties 3 to 4 days a week but next year my Wife and I will be freed up a bit more so planning to get away down south more often.
You don’t appreciate dark skies unless you also image from a big City like Sydney. When I’m down south under B3 and the subs start rolling in , you say to yourself why do I bother imaging up in Sydney , it’s simply chalk and cheese. Thankfully we have Narrowband

Cheers
Martin

[strongmanmike]

I agree, I used to image from inner suburban Newcastle (https://pbase.com/strongmanmike2002/image/141334067/original), not only were the skies a lovely light grey/white, the seeing was crap too, then I got out to near Kurri Kurri (https://pbase.com/strongmanmike2002/image/107700957/original), west of Newcastle and it was darker (B3-4) but still ordinary seeing, then I moved to semi rural skies outside Canberra (https://pbase.com/strongmanmike2002/image/147003522/original) (B3) and at 600m (https://pbase.com/strongmanmike2002/image/157983427/original) and it was much better, both darkness and seeing....now in Tinderry (https://pbase.com/strongmanmike2002/image/173146506/original), well, the journey is kinda complete, would have to leave Australia now in order to get a significant improvement :D....true dark skies are wonderful :stargaze:....and so are grandchildren...hope to have some too...eventually...:thumbsup:

Mike