1: Function MainWindow.MainWindow.GetSkyRADec( MainWindow.MainWindow, int32, int32, byref double, byref double, byref double, byref double ) as boolean
2: Sub MainWindow.MainWindow.MouseMoveOnSkyChart( MainWindow.MainWindow, int32, int32 )
3: Sub MainWindow.MainWindow.Sky_MouseMove( MainWindow.MainWindow, int32, int32 )

User description of above error trace:

I was trying to scroll the list of objects on the Objects tab using the arrow keys. It's possible I hit some other key instead, maye a "Page down" key or "End" key instead. AstrroPlanner unexpectedly switched to the Sky tab and then brought up the Application Exception dialog. I expect that AstroPlanner will keep running, altho I haven't tested that yet.

Fixed.