The term 'supermoon' was coined by astrologer Richard Nolle, not an astronomer.
The supermoon happens when moon is full and makes it closest approach to Earth in her orbit.
Although the full moon and perigee didn't exactly overlap this month, the supermoon next month — on Sept. 28, 2015 — will coincide with the full moon, making it the biggest and closest moon of the year.
This month’s perigee occured on Sunday, that’s about 18 hours after the Saturday night full moon. So the August supermoon was not quite full.
What skywatchers are most interested in is perigee, the date and time when the moon is closest to Earth.
Because the moon has an elliptical orbit, instead of revolving around the Earth in a perfect circle, there is a time when it is farthest from us — the apogee — and a time when it is closest — the perigee.
There were four supermoons earlier in the year, and there are two supermoons remaining in 2015: September 28 and October 27.