15-01-2023, 17:38
Hi Simon and Christian,
We discussed on this topic in our French team reviewer las week.
Yes I confirm here the assumption related to Rolling Shutter mode for CMOS cameras. To help observers in resolving the latency they are meeting, if they don't perform a real test on a led driven by an accurate PPS output we should ask them this two questions :
FPS max : What is the maximum frame per second rate the camera is able to deliver for a full frame output with a very short exposure time. This data is given by ZWO or any camera manufacturer. Keep in mind that Sharpcap with the free version is limiting this maximum rate.
Y N° lines : And what is the size of the matrix in vertical or how many lines the chip is delivering. This number could be a little more larger than the vertical size of the picture due to additional blanking lines and occulted lines.
In inverting the product of the two figures :
1/(FPS x Y N°lines)
you get the delay of the exposure start per line.
Therefore when you process an occultation, if the time stamping is driving the start of the exposure of the first line you get your recording latency in getting the Y line number where the occulted star image is falling on. With the poduct of this number with the delay of the exposure start per line you get the latency to add on your report. This work also in ROI mode.
Astroregards
Thierry
We discussed on this topic in our French team reviewer las week.
Yes I confirm here the assumption related to Rolling Shutter mode for CMOS cameras. To help observers in resolving the latency they are meeting, if they don't perform a real test on a led driven by an accurate PPS output we should ask them this two questions :
FPS max : What is the maximum frame per second rate the camera is able to deliver for a full frame output with a very short exposure time. This data is given by ZWO or any camera manufacturer. Keep in mind that Sharpcap with the free version is limiting this maximum rate.
Y N° lines : And what is the size of the matrix in vertical or how many lines the chip is delivering. This number could be a little more larger than the vertical size of the picture due to additional blanking lines and occulted lines.
In inverting the product of the two figures :
1/(FPS x Y N°lines)
you get the delay of the exposure start per line.
Therefore when you process an occultation, if the time stamping is driving the start of the exposure of the first line you get your recording latency in getting the Y line number where the occulted star image is falling on. With the poduct of this number with the delay of the exposure start per line you get the latency to add on your report. This work also in ROI mode.
Astroregards
Thierry