Strange... the arcsec/pixel is calculated from the focal length and the pixel dimensions. The next step is to let me see an entire ACP run log. They are at My Documents\ACP Astronomy\Logs\mmmmddyy\... Find one with this error in it. Please attach the log file (see below), don't paste it into a message. I'm guessing there will be many ha ha.

**Script Error (Tracking has been stopped)**
Source: PinPoint.Plate
Message: The value is out of range.: ArcsecPerPixelHoriz
Location: line 1533 column 33.

The only other issue I can think of is the camera giving a crazy pixel size (through MaxIm). That would do it. But seeing the entire log will allow me to see.