QHY294C keeps exposing the 1st frame after changing exposure time

[dudugaz]

Hi Robin,
I too have this problem with my QHY294c and QHY294M-Pro and that I did not have with the QHY168c. I have never succeeded in making this QHY168c work without its power supply.
It is not constant and my camera when it is on my landline is connected for its power supply and the USB on a Powerbox V2.
For exposures of 30 or 60s it is fine, but as soon as you go to 120s, 180s or 240s for example you have to be patient especially when you launch a capture and you want to visualize the 1st exposure with a processing software (Siril, Pixinsight, ...) to check if it is suitable. I have the impression that on EZCap the problem is under control.
Best regards
Dominique

[admin]

Hi folks,

hopefully I have some good news on this particular problem – I have been working with Dr Qiu from QHY over the last few days and I think we now have a solution to the problem of the crashes when these cameras are put into still mode. I'm hoping to upload a new version of SharpCap 3.3 this evening that will contain that fix. Once you are able to put these cameras into still mode, the issues of incorrect frame length should hopefully go away.

Cheers, Robin

[bflachsbart]

Hi Robin,

thanks for this good news!
I'm already excited to check out the new version, hopefully the delay will vanish after being able to switch to still mode

best regards
Bernd

[dudugaz]

Hi Robin,

Great I will end up switching to version 3.3 for good. In fact I just did a test on SGP to check something else, a history of bad grip on 240s (very visible bayer matrix). On SGP no problem matrix on the 240s and,for your information, no delay problem.

Regards
Dominique

[dudugaz]

Hi Robin,
I had some darks to redo and given the very bad weather, I took the opportunity to test with the last beta version 3.3 the still mode option on. The management of the delay seems resolved but It is not very stable and on 240s exposures this bug on the 4th exposure. I made several attempts. With EZCap as with SGP no worries except that I like Sharpcap less in use.
Regards
Dominique

[bflachsbart]

Hi Robin,

I've just tested the Beta 3.3.7313.0 and unfortunately I have to report good AND more bad news.

The good news is that I was able to switch to still mode without a crash.
While in still mode, changing the exposure time back and forth didn't lead to the significanty extended exposure times as before.
However, I observed that the exposure time isn't as exact as before:
No matter what exposure time I'm selecting the actual exposure time is usually 1-2 seconds longer than the nominal value for each (!) frame.
So e.g. 8 sec would probably always expose 9.5 sec and 30 sec about 31.5 sec.
I suspected that the USB traffic setting might be the culprit but even with USB traffic set to 0 the additional 1-2 sec persist.

But the worst problem is that the frames have strange banding and corner artifacts and are'nt usable at all.
I've attached two screenshots, a "Dark" frame and a "Flat" frame with some light. The Dark frame shows a vertical banding issue while the Flat frame seems to be black/unexposeed on the left and top. These issues are as well visible in the actual captured frames when inspected with PixInsight, so it's not just a display issue.

Another strange thing is that the sensor is way less sensitive in still mode:
In video mode a 0.5 sec exposure with my flat panel at lowest setting gives me a histogram somewhere in the middle at 1600 gain so it would be the proper exposure range for flat frames.
In still mode with exactly the same camera settings the histogram is all the way to the left and I can even increase the Flat Panel brightness to the maximum without the histogram moving to the right more than say to the 20% range.

best regards
Bernd

[admin]

Hi,

thanks for the update - I was really hoping that I had solved the 294 problems, but it seems I've just opened the door on more issues.

The blank band looks like a sort of border area around the image - some cameras have an 'overscan' area, but as far as I know I haven't done anything to try to get data from this area.

The brightness thing could be settings not carrying through the still/live switch properly - making that switch requires almost closing the camera and re-opening it, and it's possible that some settings could get reset. Try making small adjustments to the controls like gain etc to see if any small adjustments give a big brightness boost - that might indicate a control that is being reset.

Unfortunately, I don't think that I'm going to be able to do much more about this at the moment – although I've had a lot of good support from QHY recently on this issue, it's now the Chinese New Year, which they take very seriously in terms of taking time off work (and who can blame them!).

Cheers, Robin

[bflachsbart]

Hi Robin,

You are right, the sensitivity issue seems to be simply related to the settings not being applied "behind the scenes".
I switched from live mode to still mode without setting the exposure time again because I supposed it would be still active.
But the camera seemed to switch to the shortest possible exposure while the UI still showed the 0.5 sec setting.
After changing the slider a bit and setting the exposure again explicitly to 0.5 sec the histogram behaved rather comparable to video mode.

Regarding the Ovrescan area I thought about this too because I had a similar effect once when I used the 294c in ASCOM mode with SGP and inadvertantly forgot to disable Overscan. But the frames also had larger pixel dimensions in that case.
With SharpCap the frames are exatly the nominal pixel widh and height, i.e 4164 x 2796

I exposed a longer dark frame today and as can be seen in the screenshot, now the left and top border which I saw in the flat frame is also visible in the dark frame in addition to the vertical banding.

Perhaps it actually is the overscan area and the frame is cut off respectivly at the lower right side to match the nominal pixel dimension ?

best regards
Bernd

[admin]

Hi,

ok, thanks for the further info - it sounds like I need to re-send all the control values to the camera after mode change which will probably fix problem 1. I will wait until QHY are back online to ask if they have any ideas about the overscan (sort of) problem.

cheers,

Robin

[didiflei]

I have the same Problem with my QHY268C in SC 3.2.
In Sharpcap Ver. 3.3. Beta it's not possible to receive a Frame in the Live-View-Mode.