AstroDMx Capture - Technical Help for Windows

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Any procedures suggested on this website should be used carefully and will be at the users risk. Performing these procedures implies acceptance that the responsibility is with the user and the author of this website will not be held
responsible for any problems arising from the use of these procedures.

The information and procedures on this page are specific to Microsoft Windows.

DSLR Cameras under Windows


AstroDMx Capture is able to directly control many Nikon and Canon DSLR cameras. If your DSLR camera supports tethering then the camera can be connected to AstroDMx Capture and controlled in the same way that other astronomy cameras
are used.

This functionality exists in all builds of AstroDMx Capture but, in order to use this functionality in Windows, it is required that the DSLR camera driver is changed.

If you attempt to connect a DSLR without changing the driver, then you will be presented with the following message

dslr error message without correct driver


NOTE: This procedure should only be run once. NOT each time you wish to use a DSLR with AstroDMx Capture. Follow the procedure at the bottom of this article if you wish to remove the new driver.

It is a simple matter to change the DSLR driver (and simple to reinstall the original, manufacturer supplied driver). In order to change the driver, you will need to download Zadig. Zadig is an open source tool specifically designed for this purpose. You can download Zadig from the link directly below.

Once downloaded, double-click on the Zadig executable to run the program. Zadig will look like this.

Zadig Application

Connect your DSLR camera and click on "Options" and select "List All Devices". This causes your currently connected cameras to be shown in the drop down list. Now select your DSLR camera from the drop-down list, this will be shown as "Canon Digital Camera" or "Nikon Digital Camera".

The screenshot below shows a Canon DSLR selected and ready to have its driver changed.

Zadig Application

Make sure that the driver after the green arrow is set to "WinUSB". In all probability this will be default and so will not need to be changed. If the driver is different, then use the arrow keys to select "WinUSB".

Once Zadig looks similar to the screenshot above, click on "Replace Driver". This should ONLY be done ONCE. It may take a few minutes for this change to be come active. Once complete, you will see the following.

Zadig Application

You are now ready to use DSLR cameras in AstroDMx Capture. This procedure will only need to be done once, however, if you want to revert to the original driver (supplied by Windows) then this can be done by following these instructions.

  1. Connect your DSLR driver,
  2. Go to Device Manager,
  3. Locate and expand "Universal Serial Bus Drivers" and select your camera name. Once you have done this you can remove the driver in the usual way.

NOTE: If you have run the above procedure more than once, you will have to remove the WinUSB driver more than once. The exact number of times is equal to the number of times you had run the Zadig procedure.

Windows 7

AstroDMx Capture for Windows is NOT currently supported on Windows 7. It is possible that specialist Astronomy cameras, such as the SVBONY SV305, ZWO and QHY, may work on Windows 7 but this is untested. Certainly, UVC cameras will
NOT work. Examples of UVC cameras are the SVBONY SV105, SV205 and general webcams.

Future versions of AstroDMx Capture may be released with UVC support for Windows 7.

ZWO USB2 Cameras

The Problem

When ZWO released its range of USB2 cameras (for example, ASI120MC), they were primarily designed to be used on Microsoft Windows. By default, these cameras use a non-standard maxPacket size of 1024 instead of 512, while this works on most Windows computers, it can be a problem on newer hardware.

Older computers had both EHCI and xHCI USB controllers. If this is the case for your computer then ZWO USB2 cameras should work correctly. However, many modern computers no longer have an EHCI controller, if this is the case then USB2 ZWO cameras might not be detected. This affect should be observable on any Windows capture application, not just AstroDMx Capture.

If this problem is present, "Device Manager" should show the ZWO as a failed device and so will not work in any capture application.

Possible Fix

If you discover that your USB2 ZWO camera is not being detected, then you can flash your camera's firmware with the compatible firmware. The compatible firmware changes the maxPacket size from 1024 to the standard 512 and should allow the camera to work correctly on xHCI USB controllers. The firmware can be downloaded from the ZWO website.

You should test your USB2 camera before attempting to flash the firmware.

ZWO USB3 cameras are not affected by this problem and should work perfectly with AstroDMx Capture on Windows.

Known Issues | All Platforms


There are some issues with the macOS build of AstroDMx Capture. If a Mac has a high resolution screen (greater than 1920 x 1080) and has display scaling active then the preview display does not render correctly. I am investigating this issue and will release a new version once I have a fix. For now, if using a Mac computer with a high resolution display, display scaling should be disabled.

All Versions: ZWO USB2 Cameras

There are various issues with the ZWO USB2 cameras running under Linux and macOS. These issues are not caused by AstroDMx Capture but are due to these cameras having an invalid max packet size. These issues do not affect ZWO USB3 cameras.

For more information about these issues, please see Technical help for Linux or Technical help for macOS page

USB2 ZWO cameras can also be problematic under Microsoft Windows if the hardware is relatively new. For more information about these issues, please see Technical help for Windows

Show Previous Versions

Hide Previous Versions

Version 0.90.2

Due to a possible issue with the QHY SDK, AstroDMx Capture occasionally crashes when changing resolution or pixel format. Although this problem was confirmed in 0.88.2, it has not been observed in 0.90.2. This issue is mentioned here just in case it still exists.

Version 0.88.2

Raspberry PI 32bit (armhf) Due to a recent update to the 32bit Raspberry Pi OS distribution (Buster), it is not currently possible to use AstroDMx Capture in hardware acceleration mode. If you are using the 32bit Raspberry PI OS then you should switch to software acceleration by clicking on Options and then making sure that hardware acceleration is disabled.

Fedora 34: On some installations of Fedora 34, AstroDMx Capture fails to start. In order to fix this, simply remove from /usr/local/AstroDMx_Capture/lib . I will make a maintenance release to fix this problem in due course.

Version 0.84.7

If a DSLR is set to anything other than Manual then changing the exposure causes a segmentation fault and so AstroDMx Capture crashes. Make sure that the DSLR is set to Manual.

Version 0.78.5: x86-64 Linux

Some ZWO cameras show multiple error messages during the connection routine. This issue will be fixed in the next release but for now, it is safe to dismiss the messages.

Version 0.78.3: x86-64 Linux

Version 0.78.3 requires a CPU with the AVX instruction set. All CPUs manufactured from 2009 should have this support. If you have a CPU manufactured before 2006 then you should not upgrade to 0.78.3.

Version 0.68.1: Ubuntu 20.04 Problems

Problem 1: Ubuntu 20.04 introduces an incompatibility with the version of distributed with version 0.68.1. If AstroDMx Capture does not start on Ubuntu 20.04 then remove which
is located in /usr/local/AstroDMx_Capture/lib

Problem 2: New builds of Ubuntu 20.04 cause AstroDMx Capture to take about 20 seconds to start. Systems upgraded from previous versions of Ubuntu are not affected.

Version 0.66.x: Raspberry PI QHY Cameras

Due to an issue in the QHY SDK, long exposures sometimes take longer than expected. Depending upon your timeout settings, the connection monitor might reset the camera. The timeouts can be changed or the connection monitor can be
disabled from the options drop-down menu.

Versions 0.50.x and below

If multiple camera controls are changed during a long exposure then the last control will take effect, all others will be cancelled. For example, if the user changes the exposure to one minute and then immediately changes the gain,
then the exposure control will be cancelled. To avoid this issue, change one control and wait for the exposure to complete.