I recently read an article about "allias effect" (Think I have that right) anyway, the observation was that during an eclipse (lunar) that a pendulum increases speed (albeit slightly)
The article went on to say how mysterious this was, and how no one could figure out, or come up with theory as to justfy why this was so..........

I do not understand the confusion, if I do understand the question ?
But during an full lunar eclipse, would we not experience a slight lessoning of gravity on earth, (as now we have Moon and Sun pulling in unison against earth's gravity) resulting in a increase in the speed (slight) of the pendulum ?

Someone correct me if I'm wrong.......