Of all the full moons that occur in a year, the one that will be near its peak Saturday night is perhaps best known: the harvest moon.

Its popularity is related almost certainly to there being few astronomy-themed songs quite so catchy as the oldie titled “Shine on, Harvest Moon.”

Harvest moon is the full moon closest to the autumn equinox, which arrives here Sept. 22 and which traditionally marks the beginning of fall. For meteorologists, fall starts Sept. 1, though the heat of many recent days has suggested nothing but summer.

Insulated by the laws of celestial mechanics from the variation of daily temperature, however, lunar phases do not change.

The harvest moon became full Friday and will remain big and bright as it looms above us Saturday night.