DSO Pseudo-Lucky Imaging with Live Stacking

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
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MarMax
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DSO Pseudo-Lucky Imaging with Live Stacking

#1

Post by MarMax »

I've been in a recent discussion on CN regarding short subs and live stacking for EAA. Not exactly lucky imaging but perhaps more like "fortunate" imaging. This is the discussion thread.

https://www.cloudynights.com/topic/8264 ... p=11934147

The unknown, because I've not had a clear sky in days, is if short (1/2 to 1 second) subs can be live stacked with a small sensor (290) using restrictive FWHM and Brightness filters to cull bad frames. I plan to try this with a C11 Hyperstar (f/2) and the ASI290MM, which should be quite fast and sensitive. The rig is a CPC Alt-Az mount connected via a USB hub to the HP Pavilion laptop (i7 and Windows 10).

On a side note, the last time out with the QHY183C when running 10 second subs I was having some live stacking delays. There were instances of a good 30-50 second lag but there were no dropped frames. The stack count would just suddenly jump up by the number of delayed frames. The FWHM values would also lag and then update all at once.
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Re: DSO Pseudo-Lucky Imaging with Live Stacking

#2

Post by admin »

Hi,

the issue with very short exposures is that you may not be collecting enough light to optimize the noise levels of the captured image relative to the camera read noise - if that is the case then the stack may end up not really improving as much as it should with added frames. Anyway, the smart histogram functionality will work that out for you by measuring the sky background brightness. Short exposures also increase the amount of work that needs to be done by the live stacking calculations, but using a smaller sensor like the 290MM will offset that.

On the live stacking delays, the two things that are possible are 1) that the camera is dropping frames without telling SharpCap - doesn't sound likely in this case since the stack count would not increase by 3/4/5 suddenly or 2) that the processing is taking too long. You can check the latter by looking in 'Status' tab of the live stacking UI, which gives both the amount of time needed to stack each frame and the amount needed to display the frame. It would be interesting to know if it is the whole SharpCap UI freezing up or just the live stacking not updating but menus etc working - that would help narrow down the possibilites.

cheers,

Robin
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carlomuccini
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Re: DSO Pseudo-Lucky Imaging with Live Stacking

#3

Post by carlomuccini »

It has also happened to me for a few weeks (I always update SC with the new version) and this did not happen before
The livestack works fine but even for 30s it does not update the status window, then suddenly it recovers.
But it's just a window update issue, the live stack works great

ZWO ASI 294MM in bin 2: 15s gain 300

Among other things, I found it much better not to use the dark and I avoided the veil with background lines that appeared before; however, there remain some "rows" of hot pixels when I sum the FITs later

Here IC5070
TEC140
ASI294MM
4x900s
Bin 2
2072 x 1410 pixel

Carlo
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Re: DSO Pseudo-Lucky Imaging with Live Stacking

#4

Post by admin »

Hi,

so I have a new feature coming up with hot pixel removal without dark frames (tomorrow's update) which should help.

Logs from any cases of of lagging live stack would be welcome - I will investigate.

cheers,

Robin
MarMax
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Re: DSO Pseudo-Lucky Imaging with Live Stacking

#5

Post by MarMax »

That new hot pixel feature sounds nice. I'll look forward to testing it out.

I'm also really bad about saving logs but I will try to remember next time I'm using the QHY183C.
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