QHY294C keeps exposing the 1st frame after changing exposure time

bflachsbart
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QHY294C keeps exposing the 1st frame after changing exposure time

#1

Post by bflachsbart »

Hi,

I'm struggeling with a strange problem using the latest SharpCap Pro version 3.2.6457.0 with my QHY294C.

Whenever I'm changing the exposure time, the first frame in preview mode is often exposed considerably longer so that the camera seemingly doesn't stop exposing. The problem doesn't happen every time but it's probably more prevelant with longer exposures.

Say I'm changing the exposure time from 5 sec to 90 seconds, then the first frame sometimes is exposed way longer than 90 seconds e.g. > 120 sec or so and seems to be stuck. However, after some time the frame finally rolls in no matter how long it took... and after that all the following frames are exactly exposed with the chosen exposure time as it should be.

Today the first 60 sec frame took nearly 180 sec ere it was dowloaded by SharpCap. In all cases SharpCap even states this prolonged exposure time in the status bar. As I said, after the "obstacle" of the first frame is taken, all is running smoothly afterwards.
I've also observed it with short exposures e.g 4 sec but the delay from 4 sec to for example 4.7 sec is so short that it's barely recognizable.

At first I thought that it might be a USB cable issue and in deed I had inadvertantly used an erratic cable when I first encountered this problem.
UsbTreeView revealed that it only connected Highspeed even though it was an USB3 cable, so I supposed I had found the cuprit.

But I'm still having this effect with a new USB 3.0 cable plugged directly in my computer without using a USB hub. According to UsbTreeView it's connected with USB Superspeed mode.

Since I used to shoot very short 30 sec subs until recently and encountered this problem on my first usage of 90 sec subs I now rather think that I didn't get aware of it with the shorter subs but the problem was already existing nonetheless.

I'm not sure if this is a SharpCap or driver problem or if it's supposed to work like this with CMOS cameras ?

I've tested different QHY driver versions and different SharpCap setting like increasing USB traffic, turning off the DDR buffer and so on, but to no avail.

best regards
Bernd
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#2

Post by admin »

Hi Bernd,

does your camera have a 'Force Still Mode' option in the controls on the right? If it does, then does changing the setting of that have any effect on the problem?

cheers,

Robin
bflachsbart
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#3

Post by bflachsbart »

Hi Robin,

yes it does have the "Force Still Mode" option but I can't use it because SharpCap crashes if I set it to "on".
I've read here in other people's topics too that this option isn't working with the QHY294C.
But I will check it out again tomorrow using the latest QHY driver.

Do you have any other suggestion what I might test to nail down that problem?
Or is it a "normal" behaviour which perhaps related to the internal camera buffer ?

thanks a lot
Bernd
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#4

Post by admin »

Hi Bernd,

ideally, the still mode option would be the way to go - running any camera in video mode for long exposures is full of risks of this sort of problem.

Could you try the latest beta version in still mode (from https://www.sharpcap.co.uk/sharpcap/sha ... s/3-3-beta) and submit a bug report when the crash happens. I will try to investigate whether we can work out a fix to this still mode bug (unfortunately I don't have a QHY294, and all my QHY cameras work fine in still mode ...)

cheers,

Robin
bflachsbart
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#5

Post by bflachsbart »

Hi Robin,

As you suggested, I've tried setting the still mode with the beta which led to an immediate crash and I submitted the bug report.
After a crash SharpCap start with the still mode option still set to on, but not a single frame is transfered this way which also suggest that the option doesn't work for a 294C

I've also tested the strange 1-st-frame-longer effect with different combinations of SharpCap Version, QHY driver version and sdk versions, replacing the qhyccd.dll in the SharpCap folder in the latter case. But the effect persists.

But I've found out something interesting nonetheless:
The first frame is almost always exposed excatly 2 times the chosen exposure length. Sometimes a little longer but never ever more than three times the nominal exposure length.

e.g. if I set a
- 4 sec exposure the first frame takes 8 sec
- 8 sec exposure the first frame takes 16 sec
- 30 sec exposure the first frame takes 60 sec
- 60 sec leads to 120 sec and so on...

Very rarely it takes a bit longer, which might be due to the fact that the camera is perhaps first finishing the current frame which I kind of interrupted by changing the exposure time. But as I said the maximum seems to be the factor 3.

Now that I know this systematic behaviour I think I can come to terms with it, at least as a workaround until the still mode option hopefully works with the QHY294C.

When taking my 90 sec subs of course I got nervous when the first 90 sec exposure in preview mode ran too long and wasnt even finished after 150 sec or so.

But the timimg is now absolutely predictable so the first frame will take bewteeen 2 x exposure length and max 3 x exposure length.
After that, all is running as expected.

best regards
Bernd
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#6

Post by admin »

Hi Bernd,

unfortunately this is the same behaviour I have seen before with the still mode crashes - the QHY SDK is writing to memory that it should not be using and crashes the application. It's not even doing something that might seem obvious like running past the end of the memory that SharpCap sets aside for the image - it's somewhere else entirely. I don't think I'm going to get this sorted without a QHY294 to test with :(

Glad to hear that you are happy with a workable (if not ideal) situation to get imaging!

cheers,

Robin
bflachsbart
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#7

Post by bflachsbart »

Hi Robin,

just FYI, I've found evidence in the QHY Forum that there are in deed some CMOS chips which throw away the first exposed frame!

Most notable is the following quote:
About the delay issue,according to Dr.Qiu,when set different expose time,camera will wait until the end of current frame expose,and it will give up the first frame that you cahnged expose time,camera will output image data from second image.So this make the actual time is too long.About to solve it,Dr.Qiu told me,it need setup register to immediately stop current frame expose,and close the function of waiting second frame. This can let software readout image faster.But the issue is this function is for the chip that product by Sony,but the QHY5II's chip is producted by Micron,so he's afraid the QHY5II has no this function.So Dr.QIu advice you use Sony chip camera,for example QHY5III290M.
Best Regards,
QinXiaoXu


Here is the link to the topic:
https://www.qhyccd.com/bbs/index.php?topic=8312.0

That's quite interesting because it's an exact description of the delay I'm experiencing.
So after all it's probably normal although it seems strange :)

greetings
Bernd
DiligentSkies
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#8

Post by DiligentSkies »

Hello bflachsbart,

I too was experiencing a very similar problem with my QHY268c camera.

Whenever the exposure setting was changed, "The exposure count down rolled on past the new exposure length through several durations of the new exposure length before the camera recognized the change and began providing subs to SharpCap."

Once the new exposure length starts to provide subs to SharpCap, "Everything works smoothly until you change the exposure length again."
At least that was my consistent experience!!!"

Additionally, while waiting for the new exposure length to start to provide subs to SharpCap...
SharpCap was handling the issue very well, since it appears Dr. Glover has programmatically captured this EXCEPTION and SharpCap's seems to just happily wait for the camera to provide subs on the new exposure length.

Yes it was very frustrating... since changing the exposure length is a very common practice to zero in on finding the optimal sub and turning over finding this optimal to the smart histogram analysis... Where SharpCap's smart histogram function is going to put the camera through several exposure length changes, back to back... just added up to extensive time spent waiting for the camera to sync up in running the analysis.

But I found a solution that is working for me.
Once I did this, "This persistent problem went away, completely."

Referencing the part of the QHY268c manual where QHY says...

1. How to avoid camera stuck?
per the QHY manual...
Is the voltage of the USB interface high enough? Some computers have a USB interface voltage of less than 5V. This may cause the camera to get stuck. In this case, you can choose to connect the computer to the camera by using the USB3.0 Hub with power supply, which ensures that the camera gets 5V.

Luckily I already had a powered USB 3.0 hub that I was using to USB hub my guide camera and mount.
However, "What I had been doing was connecting my imagining camera directly to my laptop's USB 3.0 port out of fear of dropping subs if I put the camera on this hub with all the other data traffic going on through this powered USB 3.0 hub.

Once I did this the problem went away, completely.

Hope that is helpful to you.

Sincerely,
Mark
bflachsbart
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#9

Post by bflachsbart »

Hi Mark,

my camera is already connected to a powered USB 3 hub, namely to a PegasusAstro Pocket Powerbox Advance.
It has a quite good reputation to provide flawless voltage to the connected devices so I suppose I'm on the safe side power wise.

But I'll check if perhaps using a different port in this hub for the camera changes the behaviour.

Thanks a lot for your feedback nonethless!

best regards
Bernd
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Re: QHY294C keeps exposing the 1st frame after changing exposure time

#10

Post by admin »

Hi Mark,

that's interesting information – thanks for sharing.

I've seen other cases with other brands where cameras are now failing to work reliably if they don't have external power connected to them. Some brands are starting to move from the external power being an optional thing just to provide power for the TEC to requiring external power for the camera to work at all. From their point of view it's better to have a camera that absolutely requires 12 V power than to have one that mostly works without it, since the times that the camera fails to work often become support requests...

Cheers, Robin
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