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M51 first try at Live Stacking Lucky Imaging

CMOS dso
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#1 jnanof

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Posted 22 May 2019 - 04:32 PM

TLDR: Live stacking in SharpCap, 15 second exposures, need to guide/dither for walking noise.

 

So I tried SharpCap live stacking last night. I did not take care to limit stray light, get perfect darks and no flats. was just messing around to see what I could get. I spend half my imaging time wasted on guiding issues so I tried 15 second exposures. I thought my focus was perfect but maybe it slipped or maybe seeing was just that bad last night. Had consistent 15 MPH winds and very turbulent skies. Even at such low exposure times, the large 30+ Arc-second PE combined with tiny pixels, shows itself 
So this was NO guiding at all, right at zenith and right on meridian. Clouds came and went as well as great to crappy transparency.
My biggest take away though is the need for dithering of some sort. I guess next time, I will guide and dither. I did not know that could be done using SharpCap as I usually use APT.
I will also try taking 15 second exposures and save to file every 10 minutes, then stack several of those. Still researching. But, this gives my a lot more hope for imaging with limited time and quality of gear. It will never be as good as dedicated SNR based exposures and proper stacking and calibrating but I am pleased with my results.

I am also wondering if the walking noise would not be so bad if the stacks were limited to 50-60 subs. I did not notice it until I was at the 30+ minute mark. I'd love some feedback on how to get a nicer stack/rejection using Sigma clipping too. 

This was one live stacked image of 206 @ 15 seconds LUM Gain 111 (unity), offset 5, ASI183MM DIY cooling, AT65EDQ scope and iOptron EQ45 mount. Processed in PI. Nothing I can do about the "walking/raining" noise at this point but will try again next clear night.

M51

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#2 mikefulb

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Posted 22 May 2019 - 05:16 PM

Maybe just bump the mount every 20 frames using the hand controller at a low speed to simulate dither.



#3 jnanof

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Posted 22 May 2019 - 05:19 PM

Maybe just bump the mount every 20 frames using the hand controller at a low speed to simulate dither.

I thought of that too but would rather not babysit. I could use PHD2 manual guide. 



#4 TinySpeck

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Posted 22 May 2019 - 05:23 PM

Pretty nice for only 50 minutes of integration and all your challenges!  How dark were your skies?



#5 jnanof

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Posted 22 May 2019 - 05:39 PM

Pretty nice for only 50 minutes of integration and all your challenges!  How dark were your skies?

about 4.5 Bortle. There were some points the transparency was amazing, then next thing, high thin clouds. Having trouble finding how to connect Shaprcap to PHD2.




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