# Estimate the maximum duration that a star is covered by the Moon.

When a distant star is covered by the Moon, the field of visibility of this phenomenon (let’s call it a shadow) moves in space at a speed equal to the speed of the Moon’s orbital motion, which is minimal when the Moon reaches the apogee of its orbit, and is 0.96 km / s. The size of the shadow area is equal to the diameter of the Moon (3476 km). But one must also take into account that the Earth rotates around its axis, and in the most favorable case, the speed of daily rotation (reaching 0.46 km / s at the equator) can be co-directed with the speed of the shadow. Thus, the speed of movement of the shadow over the surface of the Earth will be equal to only 0.50 km / s, and the maximum duration of coverage will be 6952 seconds, or 1 hour 55 minutes 52 seconds.