QHY174M low frame rate

[scorpion136]

Regardless of ROI size, I cannot get our new QHY174M to achieve more than 15 FPS. I'm using a brand new Cable Matters USB3 cable, the exposure length is set at 10 msec, no limit on frame rate in SharpCap. Laptop is a powerful Lenovo P1 with SSD. Cable is plugged into the USB3 port. The camera is supposed to be able to achieve 138 FPS. I'm stumped. Does anyone have any suggestions on how to get more frames/sec out of this camera in SharpCap? Using SharpCap Pro, latest version.

Thanks,
Ted

[admin]

Hi Ted,

first place to check is the 'USB Traffic' control that you will find in the controls on the right. For QHY cameras, that control needs to be turned down to get the highest frame rate (or turned up for maximum stability). If that is set to a high value then it will be limiting your frame rate, so try adjusting it downwards to see if that helps.

cheers,

Robin

[joanbdunham]

I have been attempting to solve a somewhat similar problem with a QHY 174 GPS and find that the settings for USB Traffic and Offset are important.
If USB Traffic is set too high, say =140, the fps drops to half what it should be for the given exposure setting. I find it puzzling that, after years of successful se with USB Traffic = 0 and Offset = 100, I now have issues with dropped frames and lower fps. I suspect there has been a software change that has modified how they affect SharpCap operations.
My advice is to try various setting values and look at how the fps change and whether or not you experience dropped frames. SharpCap is a great piece of software with a lot of parameters to consider but, trust me, you will find a set that works well.
BTW, lore amongst observers is that these parameters are camera specific. What works for QHY cannot be expected to work for ZWO.
Joan

[admin]

Hi,

you are quite correct - the USB traffic control for QHY is completely different to the Turbo USB one for ZWO - for a start, low USB traffic gives highest frame rates for QHY, but high Turbo USB gives max frame rate for ZWO! Similarly, gain is measured completely differently across various brands of camera...

cheers,

Robin

[Jean-Francois]

Hello,

Yes, different camera brand then different way to define the "USB transfer".
It is "traffic" or "Turbo" depending on the camara brand.
It modify the transfer between the camera (driver) and the computer (USB bus or something similar).
A low value can be interpreted differently with different camera brand.

On my ToupTek camera ... it has only 3 possible setting position "0", "1" or "2" ... with "2" for the maximum data transfer.

One point ... if you have during the LiveView already some dropping frames ... then it will be not better during the capture and saving on the disc.
One setting fine in LiveView is not necessary fine during the capture of a film.
And in addition ... it could depend on the maximum data transfer on the disc. In this case some SSDs are OK for the first GByte, but then no more for larger file. Or for some additional complication ... some SSD can be fine at the beginning, but much slower as soon as the disc is nearly full.


Robin ... not concerning the low frame rate ... but what happen during the memory buffering in SharpCap ?
If SharpCap can not save all the frames on the disc ... it saved it temporary in memory.
What is with the timestamp ? Are the timestamps correct while the individual frame was received by SharpCap and so the timestamp can be determined. The saving on the disc later will not change the timestamp.
And this ... independent from the file format (SER, ADV or FITS) ?


If one observation needs very short exposure, then the frame rate will be high ... but maybe with some dropped images.
The first is to consider using binning (ideally "hardware" binning in the camera) or to use a ROI. If it is not possible or does not help, then it could be possible to change to 8bit (if not yet used). The 8bit data will double the transfer rate (I guess, I cannot check it now).

Regards,
Jean-Francois

[admin]

Hi Jean-Francois,

SharpCap properly handles the timestamps in the case that it needs to hold frames in memory before the disc is ready to write them. The timestamp is attached to the frame at the earliest possible point (as soon as the camera SDK delivers the frame to SharpCap) and is kept with the rest of the frame data until it is ready to be written out.

cheers,

Robin

[Jean-Francois]

Hello Robin,

OK, thanks for the confirmation.
One point less to think about.

Regards,
Jean-Francois

Note ... tomorrow is maybe my last day in UK for the next years. It was too hot during the last 2 weeks
S4 instrument is back in the transport container and it will travel back to Germany in June.

[admin]

Hi Jean-Francois,

yes, the last week or so has been officially too hot (and too dry - the rain keeps bypassing us here). Today is nicer though. Safe journeys back home!

cheers,

Robin