DITHERING PROBLEM

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
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nettid
Posts: 16
Joined: Fri May 19, 2017 12:53 pm

DITHERING PROBLEM

#1

Post by nettid »

I have a problem with the dithering in sharpcap
my exposure is 120sec
the dithering setting is:
Automaticaly dither - on
Diyher interval - 120
Max dither step - 20 px
Settle thereshold - 2 px
Min. settle time - 5 sec
Max settle time - 60 sec
When I start with dithering, after the second exposure phd2 loses the guide star
cwm2col
Posts: 21
Joined: Tue Feb 23, 2021 2:21 pm

Re: DITHERING PROBLEM

#2

Post by cwm2col »

Hi,

Robin explained an option to me that might help. the dithering interval is a tad confusing, and APT for comparison does not use a interval time to start dithering, it just allows it after an number of sub-exposures, which is easier to think about.
In sharpcap, for a 240s exposure, I set the dithering interval to 230 s. That seems to allow the software to call a dither at 230s, but it waits until the 240s exposure is finished before starting the dither. When I leave the dither internal at 240s, i.e. assuming that a dither will start after the 240s exposure as would be a logical expectation IMO, the next exposure starts at the same time, mixing the operations. This could be a little clearer I think in sharpcap.
So, set your dither internal to 10s less than the frame length for example and see what happens. It worked for me, dither between frames, but avoiding a dither and a new frame coinciding.
nettid
Posts: 16
Joined: Fri May 19, 2017 12:53 pm

Re: DITHERING PROBLEM

#3

Post by nettid »

I will try it, Thanks!!!
Is It a good idea use reduce exposure while dithering?
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Re: DITHERING PROBLEM

#4

Post by admin »

Hi,

yes, really everyone should always have the 'reduce exposure' setting on... In fact I should take the setting away and make it default to on with no setting :)

With the reduce exposure setting on, SharpCap drops the camera down to 1s exposures while dithering and then puts back the correct exposure when the dither is complete - much less disruption.

Robin
cwm2col
Posts: 21
Joined: Tue Feb 23, 2021 2:21 pm

Re: DITHERING PROBLEM

#5

Post by cwm2col »

Yes, as Robin said. Apologies, I answered without checking your query was for live stacking. In that case, the check box to reduce to 1s is really very helpful. Sounds like a good idea to make it a default necessary option for livestacking.

If you were using the sharpcap 4 sequencer, for separate exposures, then the method I summarised might be useful.
nettid
Posts: 16
Joined: Fri May 19, 2017 12:53 pm

Re: DITHERING PROBLEM

#6

Post by nettid »

I use Live stack, but I process later with DSS
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