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Messages - bflachsbart

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Hi Mauro,

regarding the stray light a dews shield might also help a lot.
I've started using a dewshield last autumn to prevent dew on my SCT corrector plate, but I suppose it also blocks a huge amount of stray light falling from the sides on the scope's aperture.

best regards

Hi Mauro,

glad to hear that your flats improved with decreased brightness.

Although that might be 'also' due to my CLS-CCD, I might have to add another filter to stop UV or IR?

You definetly have to use at least an UV/IR cut filter because the 294c only has AR coating on the sensor window.
It's written in the specs:

For color camera user need to add a UV/IR filter in the light path

As far as I know this might be adding to your problem of bloated stars.

best regards

Hi Mauro,

I'm taking may flats with SharpCap and the 294c (non pro version) and a dimmable Lacerta flat field panel.
I guess your flat field panel is too bright if your exposure time is only 5ms.

I'm setting my camera to about 500 ms (i.e. 0.5 sec) and then use the dimmer to tweak the histogram a bit, so that the white peak is roughfly in the middle. It's quite normal that the green peak in this case is a lot further to the right side at about 75%. This is due to the bayer pattern which has two green pixels so there is more green signal.
You have to pay attention however that the green peak doesn't move too far towrads 100% lest it saturates.

It is also important that you don't change the focus point and filter before taking the flats.
Best would be to not touch the scope at all after imaging which of course isn't practicable.
I usually take my flats the other morning so I tear down my setup but I don't change anything in the optical path!
That's very important for succesful flats, the vignetting and size of dust donuts is depending on the focus position so don't change it for the flats!

Another vital point is to use darkflats instead of bias frames for calibrating the flats, thus you can succesfully deal with the significant amp glow of the 294c.

best regards

Image Issue Q&A / Re: 294C frame size with 21.02.26 all-in-one package
« on: March 26, 2021, 02:47:06 PM »
    I checked the image,but I'm not sure what is "strange patern at the bottom" you said,could you mark it?


You can see it in the picture of my orginal post, but I marked it here to make it clear.
It's visible when you zoom all the way in, e.g. 10:1.

The dark border at the left has two pixel width.
And the border which I described as "strange pattern" has a height of 2 pixels.

The last but one pixel row above is simply vertically repeated which leads to an invalid bayer pattern in these last 2 rows.

I hope it's clear now what I mean. I'm using PixInsight but I suppose that it can be ssen in any other application too if you zoom in enough so that you can inestigate at pixel level.

best regards

Image Issue Q&A / Re: 294C frame size with 21.02.26 all-in-one package
« on: March 25, 2021, 02:28:37 PM »

I've attached a screnshot of the EZCAP_Qt title bar showing the firmware (Firmware.PNG)
Out of curiosity I captured a frame with EZCAP_Qt and it was 4164 x 2795 in size with "Ignore Overscan Area" checked in the file menu.

As to ASCOM I've cheked out the camera properties with Profile Explorer, it also reports 4164 x 2795 which I think explains the frame size I got in SGP (ascom.JPG)

The attached Flat frame in Flats_00003.zip is taken with SharpCap, it is 4164 x 2822 in size and has the dark border at the very left and also a strange patern at the bottom.

best regards

Image Issue Q&A / Re: QHY268C Buffers Three Frames
« on: March 23, 2021, 03:25:42 PM »
I'm suffering from the same issue of overlong first frames with my 294c as well, even with the latest 21.02.26 all-in-one package.

There is a discussion about this on the ShaprCap froum


best regards

Image Issue Q&A / 294C frame size with 21.02.26 all-in-one package
« on: March 23, 2021, 03:18:24 PM »

I'm having strange frame size and perhaps overscan issues with my QHY294C (non Pro Version) and the the latest driver 21.02.26 all-in-one package.

Prior to this update I had a maximum frame size of 4164 x 2796 pixel in SharpCap with any older driver version.
With the 21.02.26 Version I get 4164 x 2822 and there is no entry for 4164 x 2796 in the dropdown.

In my light and flat frames taken with SharpCap with the 21.02.26 driver I notice a dark pixel border at the very left side, as if part of the overscan area is included in the frame. I never got this border with older drivers in SharpCap.

With SGP using the ASCOM driver of the 21.02.26 all-in-one package I'm getting 4164 x 2796.
So the same size I used to get in SharpCap with the older drivers.
Even though the frame width is the same, I don't get the dark border with SGP and the ASCOM driver.

So I wonder what is the correct full frame size for the 294C and what causes the dark border, which I didn't have with older versions and which doesn't exist in the SGP frames?

best regards


I have the same pattern in my QHY294C and I think it's amp glow.
However, it calibrates out with proper dark frames, at least for me.

In my dark frames the visibilty of the pattern increases with exposure time which also suggests that it is amp glow.

best regards

QHYCCD SDK FOR WINDOWS / Re: ONE page for drivers etc.
« on: March 01, 2021, 11:34:08 AM »
Hi QinXiaoXu,
Don't worry,this update will not lock 47MP mode for QHY294C,you still can update it to QHY294PROC.

How can I upgrade my 294C to 294PROC ?
Is there a firmware Update and instructions how to do that ?

thanks and best regards

QHYCCD SDK FOR WINDOWS / Re: ONE page for drivers etc.
« on: February 28, 2021, 09:28:07 AM »
Hi Marcel,

thanks for the hint, I didn't notice the all-in-one package at the bottom of the page.
Since the SDK 21.02.01 at the top of the page matched the qhyccd.dll version 21.2.1 of SharpCap 3.2.6480.0  I supposed I was at the latest SDK version. But you are right, the sdk in the all-in-one package 21.02.26 is newer.

So I uninstalled everything and reinstalled from the 21.02.26 all-in-one package.

I'm happy to report that the gain issue above 2000 is now solved for me and there isn't any histogram clamping as with the old stable driver.

My apologies to QHYCCD for my unjustified criticism.

One thing is very strange though:
With the old drivers I had a maximum frame size of 4164 x 2796 pixel in SharpCap which matches the specification on the QHYCCD website for the 294C.

With the 21.02.26 driver SharCap captures at 4164 x 2822 and there is no entry for 4164 x 2796 in the dropdown.
It seems that a vertical overscan area is included?
In video mode the entire frame seems to have valid data while in still mode there is a black border at the bottom and (!) at the right side.

bst regards

QHYCCD SDK FOR WINDOWS / Re: ONE page for drivers etc.
« on: February 27, 2021, 11:46:51 AM »

I've just tested the 2021.02.25 driver release which was supposed to fix all problems (?) with the 294C (non pro version) which were discussed here.

Unfortunately the gain issue described in my reply #30 on december 30th isn't fixed:
When I increase the gain setting at a given flat panel brightness the histogram is moving to the right as expected but somewhere above 2000 gain it still jumps all the way back to the left as if there is a kind of wrap around or overflow.
According to the specs the 294C should work with gain settings up to around 3500, but it seems to fall back to 0 above 2000.

I can reproduce this issue with the latest ShaprCap Version 3.2.6480.0 no matter if I connect with the native driver or with the Ascom driver. And even with EZCAP this behaviour can easily be oberved.

It's very frustrating that these problems don't get fixed.
The drop in the gain will for example prevent a succesful sensor analysis in SharpCap as another user here already described.

I'm very disapointed that there is still no driver without issues for this camera.
I've spent 1000 Euro for it and I think it's justified to expect that QHYCCD provides flawless drivers for this product?

best regards


    No,in fact,the old one is,this was released on one year ago.The 20.06.26 version is newest stable version.
    And you said you replaced the SDK for x86,which version do you replace?And why do you replace it?


thanks for your answer.

my point is, that the "lastest" ASCOM driver (please note the attached screenshot) on your website is linked to

which contains the
As you have confirmed this is an older version, so I suppose the download link is just messed up.

I've replaced the qhyccd.dll of the Ascom driver with the one from sdk 20.12.27, because the instructions of the sdk download said to do so:

Since the old ascom camera driver installation put the QHYCCD.DLL to the windows/SysWow64 or windows/system32. And the recently ascom camera driver put the QHYCCD.DLL into the programe(x86)/common/ascom/camera. We recommand to delete the QHYCCD in windows/SysWow64 or windows/system32 and put the new QHYCCD.DLL to the programe(x86)/common/ascom/camera folder.

I think I'll probably just keep using the which is working for me.
But I suggest that you check the "latest" download link on your website as it's obviously broken.

best regards

    Which camera do you use?QHY294C or QHY294PROC?And which version ASCOM driver plug-in do you use?
    I tested newest version package V20.12.29.20,it can work well with QHY294C and QHY294PROC,it can save preset and edit gain&offset.


I'm using the QHY294C non pro version.
The setup which works for me regarding the presets looks like in screenshot Ascom_okay.PNG.
It's installed from the stable all-in-one system pack (

Then I've updated the following:
1. latest driver from Download section 2020.12.28
2. ASCOM driver marked as "latest" from Download section
3. latest sdk from Download section 20.12.27
4. then I've replaced qhyccd.dll in C:\Program Files (x86)\Common Files\ASCOM\Camera\x86 with the one from the sdk

After this, the ASCOM settings look like Ascom_not_okay.PNG and I can't edit the gain settings with values > 80.

Comparing my versions to yours I noticed that the version linked as the latest ASCOM driver in the Download section of your website is which actually is older than !

So perhaps the Download link on the website is just pointing to the wrong file ?

best regards


I've checked out the latest All-in-one ASCOM Driver from the download section yesterday and have the following issue:

When trying to edit the gain settings in the named preset table, the rather high gain values for my QHY294C (e.g. 1500 or 1700) aren't accepted and the value switches back to the default value. There was also some kind of "out of range" error from the user interface when entering that value.

With the Ascom driver which is contained in the stable system pack, I don't have this issue and can enter the values.

Is this a known issue with this version ?

best regards

QHYCCD SDK FOR WINDOWS / Re: ONE page for drivers etc.
« on: December 30, 2020, 06:51:51 AM »
This fullwell capacity issues causes all the pixel values to be limited to a mean value of 48,000 counts with a bell curve distribution of possible values.  When this fullwell capacity issue is happening it is impossible to achieve a pixel value close to maximum (65,534).  I also checked that the read noise for the camera is dropping when I use GAIN=1600 so I believe that the LGC/HGC logic is working correctly.

Hi Peter,

I ran into the same problem with the full well clamping when taking flat frames at 1700 gain with my QHY294C (non pro version) the other day.

I got aware of the problem when I used the flats calibration wizard of SGP and it always recommended a 5 sec (!) exposure no matter how bright my flat panel was.

So I had a closer look at this strange behaviour using the latest Sharp Cap Version 3.2.6457.0 and the driver contained in the stable all-in-one system pack (

It is clearly visible in the attached screenshots, that while the 0.5 sec exposure histogram is okay, the 2 sec exposure histogram taken with the same flat panel brightness is faulty. On a side note: The uneven channels in the okay histogram are due to the fact that the flats are taken through a Baader UHC filter.

I've tested the latest driver 2020.12.28 and this doesn't show the full well clamping. But it has another problem, because the gain settings above around 2000 don't work as expected, the camera seems to switch back to 0 gain above 2000 or so.

Another user in this thread reported, that the SharpCap sensor analysis also looks weird with this driver and I can confirm this:
With the driver, I've never manged to succesfully finish the SharpCap sensor analysis.
With the 2020.12.28 driver, the sensor analysis succeeded but my joy was only very short. The read noise curve is increasing with a huge step about 2000 gain, as if the gain is set back to 0.
This can also be observed when looking at the histogram in SharpCap while sliding the gain control gently to the right side: The histrogram is also moving to the right side but about 2000 gain it is jumping all the way back to the very left side.

I've also tested this with the beta all-in-one system pack ( but even this driver already has this probem.

So I switched back to the original stable driver and did some further testing regarding that full-well clamping effect. I've found out that there are two ways to prevent this strange full-well clamping:

1.) setting the USB traffic all the way up, e.g. to  255
2.) leaving the USB traffic at a low value, e.g. 0 but setting the amp glow supression to off.

With either of these setting, the full-well clamping is entirely disapearing for me.

I'm not sure what to do now, I would like two have the best of both worlds/drivers.

The driver has the full-well clamping issue, but the newer drivers and 2020.12.28 have the gain issue above gain 2000.

It seems there isn't a driver for the QHY294C without any issues ?

best regards

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