Focusing with ZWO EAF

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k6inten
Posts: 12
Joined: Mon Mar 28, 2022 7:19 pm

Focusing with ZWO EAF

#1

Post by k6inten »

Hello,

I ran into this situation a couple times now and I wanted to report it. Nothing crashes, it's just a little thing.

When I am running the focus routine, I have it set to move in steps of 20 and I had been playing around with the number of steps to take and frames to capture at each step. Anyway, I set the number of frames to capture to '5' and started the routine. The focuser would move and I would get the status bar saying 'Waiting for 5 more frames' or something like that. It would count down 4, 3, then skip 2 and go to 1. Like I said, not a big deal, but a little something to look at.

I am running SharpCap Pro 4.1.13131.0 - 2/17/2025 64 bit.
ZWO EAF focuser

Attached is the log. It's pretty big but I also bet you know what you are looking for. :)

Thanks,
Keith
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Log_2025-02-23T18_45_13-7908.zip
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Re: Focusing with ZWO EAF

#2

Post by admin »

Hi Keith,

interesting - thanks for letting me know. Looking through the log, I can see that as well as skipping the '2' it is counting a -1 as well (missing zero). It seems likely that the information is being recorded twice under some circumstances, so that it counts down 2 instead of 1, but I will have to do some digging to try to work out how/why that is happening!

cheers,

Robin
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Re: Focusing with ZWO EAF

#3

Post by admin »

Hmm,

looks like this may be normal if the time taken to collect a 'sample' can be less than the time between checks for how many focus samples have been taken. The checks are carried out at 250 millisecond intervals. If you have set to average over 10 frames and the camera is running at maybe 60fps then a new sample will take about 160ms, so it's possible for two to be added between checks.

If this is the case then I don't think any harm is being done (maybe at some data points you will get the average of 6 samples instead of 5, but nothing bad will happen because of it). If it is happening at longer exposures so that the sample collection time (exposure length times number of frames to average over) is more than 250ms then please let me know as maybe there *is* an issue and I need to look deeper.

thanks,

Robin
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k6inten
Posts: 12
Joined: Mon Mar 28, 2022 7:19 pm

Re: Focusing with ZWO EAF

#4

Post by k6inten »

Robin,

I had my exposure time set to 4s so should be well outside the 250ms window...

Keith
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Re: Focusing with ZWO EAF

#5

Post by admin »

Hi Keith,

ooops, yes, that would rule out that idea... I will check again to see if I can spot anything with longer exposures.

cheers,

Robin
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