I tried my Alnitak Flip-Flat and it worked fine. I never got a COM-port denial so it appears their driver is more robust. I then noted that you said you never explicitly call Connected = false in AutoFlat so I added that to the end of DeactivateColorCalibrator and that seems to have fixed the problem with the DeepSkyDad. I'll contact DeepSkyDad but it seems like it might a good idea to call Connected = false anyway? I noticed you did that in the scripts you provided here: http://forums.dc3.com/showthread.php...6291#post96291