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Jim,
It's called an orbit not a passage. Both orbits are very slightly elliptical, close to circular. The Earth orbits around the Earth-Sun barycentre and the Moon orbits around the Earth-Moon barycentre.
The Moon has many wobbles superimposed upon it's orbit. The best known is the saros cycle, a repetitive cycle of 18 yrs 10 days and 8 hours.
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