last frame statistic

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GregL
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last frame statistic

Post by GregL » Sat Jun 29, 2019 2:55 pm

Question -- on the bottom of the Sharpcap 3.x form there is a line of information. The fields 'exposure' and 'last frame' show values -- for example, if I am making a 30 second exposure, my typical duration, the 'last frame' value is 108.1 seconds. What is this telling me?

Thanks,

greg latiak
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Re: last frame statistic

Post by admin » Sat Jun 29, 2019 10:05 pm

Hi,

The last frame value shows you the amount of time it took for the last frame to be grabbed from the camera. Typically you'd expect this to be very slightly higher than the exposure value to account for a little bit of time needed to download the frame from the camera. Of course it is the value for the last frame (the one visible on screen at the moment), so that means that if you were taking 60s exposures and have just reduced the exposure to 30s, the value may well show as 61s or thereabouts until the first of the 30s frames has completed.

Hope that helps, Robin

GregL
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Re: last frame statistic

Post by GregL » Thu Jul 04, 2019 1:04 pm

Thanks, Robin.

I don't quite understand the low level synch with my QHY183 camera -- as to whether the exposure is concurrent with transfer of the last frame from the in camera buffer to the PC, or whether these are serial events. But I gather that its probably safe to assume that the larger the last frame value the slower the USB3 connection is likely to be, yes? Anyhow, thanks.

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Re: last frame statistic

Post by admin » Thu Jul 04, 2019 9:51 pm

Hi,

Modern cameras tend to have on board memory so that the result of one exposure can be stored in the camera memory and then downloaded to the computer while the next exposure is already in progress. Apparently the high speed readout from the sensor to the on-board memory helps alleviate some issues that can otherwise be seen with CMOS sensors. I'm afraid I have no idea if the 183 model has this feature or not. However your correct that last frame times that are consistently much higher than the exposure can either indicate very slow readout or potentially a problem with dropped frames.

Cheers, Robin

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