QHYCFW3 causes SGP to close

I am using the latest generation of QHY filter wheels, CFW3. I have two. The filter wheels can be used via serial cable connected to a QHY camera, or via USB. The USB connection actually uses a serial COM port.

I have identified a repeatable problem with the USB/RS232 connection that causes SGP to simply close with no warning. Here are the steps:

  1. Open SGP
  2. Choose filter wheel (QHYFWRS232 FilterWheel)
  3. SGP then asks to import the filter names - choose YES
  4. The filter wheel is connected
  5. If I then try to open the filter wheel settings (ASCOM driver) SGP closes.

If I disconnect the filter wheel first, I can open the ASCOM driver settings. So basically, any time the filter wheel is connected in SGP if I try to open the settings it will cause SGP to close without warning.

This isn’t a bid deal since the filter wheel works properly, but I thought I’d mention it since SGP doesn’t even give a warning dialog. LOG FILE

Not all hardware supports opening the settings while the device is connected…and we have no way of knowing if they allow it or not other than trying it. However it shouldn’t cause SGP to completely quit. We have protection around the settings dialog for this case but maybe it’s putting the focuser into a bad state?


As far as I can tell the filter wheel is fine after this happens. I can immediately restart SGP and connect again. It’s not a big deal as long as I remember not to go to settings while connected.

I have had to deal with this bug (not sure if it’s the QHY driver, SGP, or interaction between the two) as well.

I have found a way to prevent SGP from shutting down on filter wheel operation: before connecting the filter wheel (QHYCFW3 via USB cable), I open the driver settings and without changing anything (it has already been properly configured), I click OK. Once that’s done, I can connect the filter wheel to SGP and execute filter change commands without any problems.

It is a mild inconvenience but the workaround has performed reliably.

Thanks for the tip lucam. I will keep this in mind and see if it works.

This sounds like something in the ASCOM driver is not being saved correctly between runs. May be worth reporting this to QHY as well if you haven’t already.

Thoughts @bmorrelltx?


Just forwarded the thread to QHY… If you want something like this tracked, you need to open a ticket or post on the QHY forum. …… Bruce

Bruce Morrell





I opened a ticket regarding this problem with QHY and there doesn’t seem to be any real resolution. Here is the reply I received from QHY:

Hi, My colleague tested it, and he tell me you should disconnect filter wheel, then open the setting. You can refer to the FAQ, it is Chinese version, but the image can reflect the issue. http://www.qhyccd.cn/index.php?m=content&c=index&a=show&catid=18&id=298 I will tell it to software colleague, maybe he will fix it later.

Most of the time this does work for me. Sometimes I have to disconnect and open the settings more than one time before it works properly. It’s a little unsettling that there could be this kind of instability, but so far I have always gotten the FW to work and it has worked fine all night long. Hopefully QHY will figure this out with a future driver update.

I specifically asked QHY about Jared’s suggestion about something in the ASCOM driver not being saved properly between runs, but that was never addressed.

Thank you, Joel.

I agree, if it doesn’t work it’s right at the beginning of the session and a couple of tries usually takes care of it. It’s not how I like my software but it doesn’t look like it’s a high priority for QHY.

The filter wheel is a beautiful piece of hardware but the driver really leaves a lot to be desired in terms of stability and consistency.

If you touch the driver settings, the program disappears. In addition. the settings for the filter wheel are not saved in SGP and you have to re-define them each time. Hopefully someone will address this issue. I have a CFW3 and it is totally unstable with SGP.

I’ve been using a QHYCFW3-L for a little while now. To be sure, SGP shouldn’t just close without warning and that’s a problem. But I believe the root of the problem is outside of SGP and related to the USB power draw and connection characteristics of the filter wheel.

Have a look at my thread on the QHY forum: https://www.qhyccd.com/bbs/index.php?topic=6812.0

One thing that I have observed is that if I have the filter wheel connected to a USB hub and I disconnect any devise from that hub, it causes the filter wheel to restart and spin again. So the connection is already a bit tenuous (any tiny drop in voltage causes the filter wheel to momentarily lose connection and restart). If there is not adequate power to the filter wheel it will whine like a busted pulley.

But here’s what works for me 100% of the time, starting with everything powered off (except the computer).

  1. Start with CFW3 disconnected from the USB hub
  2. Turn power on to everything (of course including USB hub, this is key)
  3. Plug USB cable into CFW3
  4. Open SGP, open sequence file with proper equipment defined (NOTE: do not ever try to “import” the filter positions from the QHY driver. That will cause SGP to close. Just define the filter list manually in the control panel or equipment profile.)
  5. Open the filter wheel SETTINGS. Don’t change anything, just close the pop up dialog. (first time, you’ll need to define the port setting)
  6. Connect to filter wheel.

After imaging is completed and software closed:

  1. Unplug CFW3 first
  2. Power down everything

This does really suck, but aside from how SGP closes unexpectedly I am 99% convinced this is a QHY problem.

Just to let you know I sent this thread to Dr Qui at QHYCCD… Bruce

Thanks Bruce. I do hope QHY gets this taken care of eventually. As things are now it’s impossible to use the CFW3 in a remote location when using it via USB.

Just got this from Dr Qui
Hello Bruce,

     Now we supply a power patch cable for QHYCFW3  Which can patch the power from 12V.  Please tell user to add this cable and patch the power of it. The USB port sometimes can not supply enough power for the motor. 

Best regards,
Qiu Hongyun


I am fairly certain this is a driver problem and not a power problem. I use the high-current USB port on the Pegasus Astro UPB to run the QHYCFW3 filter wheel and it is not starved for power. It doesn’t make the ugly noise when it tries spinning.

However, I still have to go through the incantation described above. I don’t have to disconnect any cable. Just open the driver and click ok without changing anything. Connect the filter wheel, spin it to a filter, and then it’s good to go.

It works but it’s disconcertingly unstable because any deviation from this sequence (for example, connect the camera first) and SGP crashes without warning.

I’m pretty sure this is both a power problem and a driver problem. The fact that you don’t experience the high pitched whine due to low power from your Pegasus Astro doesn’t mean it doesn’t exist for others (me included). I plan on getting the patch cable from the dealer I bought the filter wheel from, if the dealer ever gets any (I’ve been trying to get one from them for several months). However, frankly I don’t think this will solve the problem for me. The filter wheel works fine when my USB hub is powered up. The problem happens when I turn off the power to everything besides the computer the hub is connected to. Apparently the computer supplies just enough power to the hub and filter wheel to make it whine but not function properly. So I always have to unplug the filter wheel. In this scenario, adding a 12v power supply to the filter wheel won’t matter at all because the 12v will simply be power off with the rest of the equipment.

There’s clearly a driver issue that causes SGP to close if one doesn’t do the steps/incantation described above. But these are two separate issues.

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Can you attach a log with this? Sounds like mostly a driver issue but SGP shouldn’t die. The log you had previously attached is gone.


It figures that now I can’t reproduce this. I did update the QHY drivers a couple weeks ago so maybe the driver issue is resolved.

The power issue remains, but that has nothing to do with SGP.

Joel, you are right on both counts. It appears that the latest version of the drivers do not make SGP crash on connection any longer. Also, the filter wheel is power hungry for sure. They only port on that I can use on the Pegasus UPB is the high-current USB port. With a standard USB port I get the whine and inconsistent performance as well. I am still confused as to where the patch cable is supposed to connect. I will reach to the dealer from whom I purchased the filter wheel as well.

Lucam, it’s good to hear someone else confirm that the updated drivers fixed the problem. Amazingly, the power issue seems to have been resolved for me as well. For other reasons I completely reformatted my mount computer (NUC) and re-installed everything. Now if I leave the CFW3 USB cable plugged in I do not get the high pitched whine, even when the 12v power is turned off. I have no idea why that is the case…