when moon completely covers sun what's it called
Solar eclipse A solar eclipse (as seen from the planet Earth) is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and when the Moon fully or partially blocks ("occults") the Sun. This can happen only at new moon when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.
Midnight sun At the poles themselves, the sun rises and sets only once each year on the equinox. During the six months that the sun is above the horizon, it spends the days continuously moving in circles around the observer, gradually spiralling higher and reaching its highest circuit of the sky at the summer solstice.
Equinox In other words, the equinoxes are the only times when the subsolar point is on the equator, meaning that the Sun is exactly overhead at a point on the equatorial line. The subsolar point crosses the equator moving northward at the March equinox and southward at the September equinox.
Daytime At the Equator, the daytime period always lasts almost twelve hours in length, no matter what the season. The Sun always rises nearly perpendicular to the horizon. From the March Equinox to the September Equinox, it rises a bit north of east, and sets a bit north of west. From the September Equinox to the March Equinox, it rises a bit south of east and sets a bit south of west. The path of the Sun lies entirely in the northern half of the sky for the period from the March Equinox to the September Equinox and is entirely in the southern half of the sky from the September Equinox to the March Equinox, with the Sun passing directly overhead at noon on the equinoxes.