This weekend’s full moon will be smaller than usual. Can you tell? It is hard to tell, because every time the full moon rises in the east after sunset it looks glorious and big. If you still believe it is a big harvest moon, blame it on perception and the pleasure of watching a moon rise.

 

This weekend’s full moon, the Harvest Moon, is in apogee, farthest from the Earth than we are usually accustomed. The moon’s orbit around the Earth is not a perfect circle. In its 28-day orbit around the Earth, the moon is close, in perigee. When it is farthest it is in apogee.

 

What is the difference in distance between apogee and perigee this month? About 30,000 miles. The moon will be 252,510 miles away this weekend. Compare that to when it will be in perigee on Saturday, Sept. 28. The moon will be 222,328 miles away then. Tides will run really high and low on that day, because the moon will be close and have a greater gravitational pull as it is lined up with the sun and its gravitational pull. The moon will be in the New Moon phase.