Well, for the last month or two I've been struggling to try and get my ASI120MM to work as a guider in the latest version of PhD (v2.5d7 and 2.5d9). It's a common problem that many users have reported for a very long time, the camera output looses sync on the horizontal axis and thus the guide star is lost and guiding fails.
I've tried both the native driver in PhD v2.5 (for the ZWO ASi120MM) and the WDM drivers from ZWO and nothing will work consistently under my PC running Windows 8. On some nights I might get a few hours of proper operation and then the next night guiding will fail every 5 to 10 minutes.
As a further complication, it seems that the WDM driver when operated in the 1280 x 960 RGB8 mode will crash PhD quite frequently.
I'm running Window 8.1 on a recent generation Asus notebook with an Intel Core i3 processor and 6GB of DRAM. The guide camera is connected to its own USB2 port (although I had similar problems when it was connected to a USB3 port on my computer) and I've tried both the ZWO ASCOM ST4 driver and the Astro-Physics ASCOM GTO driver for the mount control. I have all of the latest ZWO software and have downloaded and reinstall "fresh" copies of that software at least three times.
The camera firmware has been updated to the latest release from ZWO and these problems occur even when the ASI120MM is the only active camera being used on the PC. In fact, tonight I couldn't even get the camera to run long enough to finish the calibration in PhD so I was never even able to start a guided session with my imaging camera.
When trying to use the WDM driver I set the frame exposure to 500ms and the PhD sample time to 4 seconds (thus, there were 8 frames per guiding sample). In the past, however, I've used much shorter frame exposure times (i.e. 100ms) and those also fail.
About the only variable that I haven't tried to adjust is the USB Traffic. Right now it is set to 40% and in the past I've used a setting of 80% but I don't know if a traffic setting other than those would work any better.
