The Twilight Herald
Selune is the moon of Toril. Only one side of it ever faces the planet, the other side is always shrouded in darkness and this is where most activity takes place. It is named after one of Toril’s native deities. Through careful observations and persistent divinations, sages have determined that it circles Toril at a distance of about twenty thousand miles. While Selune in the sky appears no larger than a human hand held at arm’s length, it is a world in its own right, easliy two thousand miles across.
Selune is bright enough to cast pale shadows when full. It is accompanied in the sky by the Tears of Selune, a number of smaller luminaries that spread across the sky in a great arc trailing the moon. Children’s tales tell of pirates in flying ships who come down from the Tears to raid and plunder, but no one takes these stories seriously.
Selune’s orbit around Toril is almost in the same plane as Toril’s orbit around the sun, so solar and lunar eclipses are frequent. Solar eclipses are never annular (the sun’s edge cannot be seen during totality) and almost never partial, because Selune’s shadow on Toril and Toril’s shadow on Selune are quite large. Eclipses are thus spectacular but rather commonplace. Inhabitants of any particular land do not always notice such eclipses, since the rising and setting times for Selune wander across the calendar. Solar eclipses might briefly cause nocturnal beigs to awaken, but they quickly return to sleep once daylight returns.
Selune is full at exactly midnight, the first of Hammer, and every thirty days, ten hours, and thirty minutes thereafter. The time between successive full moons is, technically speaking, one synodic month, the time from one Sun-Toril-Selune conjunction to the next. Selune makes exactly forty eight synodic revolutions every four calendar years on Toril. Thus,Selune is full at exactly midnight on the first day of every leap year, and has the same phase on any calendar day four years forward or backward in time.
One Faerunian holiday, the Feast of the Moon, is held during a full moon that obligingly shows up on or about that day. Because Selune’s synodic period is so close to the actual length of the calendar month, Selune is full around the first day of each month or on festival days, give or take a day or so. The annual festival days serve to correct discrepancies between the synodic and calendar months, with Shieldmeet providing a neccessary correction every fourth year to keep the full moon from sliding deep into each month.