July is shaping up to be an excellent month for astronomy fans.

On the night of July 27 and the early morning hours of July 28, skywatchers in the Eastern Hemisphere will be treated to the longest lunar eclipse set to occur in the 21st century, EarthSky reports.

Astronomers expect the total eclipse to last for a full 1 hour and 43 minutes, with the partial eclipse — which occurs before and after the total eclipse phase — lasting for 3 hours and 55 minutes.

A lunar eclipse occurs when the Sun, Earth, and Moon are directly aligned, and the moon's orbit brings it directly into Earth's shadow. This particular eclipse will last so long because the moon will pass directly into the darkest region of Earth's shadow, known as the umbra, which will also give the moon a reddish "blood moon" sheen.

July's full moon will happen at the same time as the moon's apogee — which is when the moon hits its furthest point from Earth in its monthly orbit, according to EarthSky. It'll be the smallest and furthest full moon of the year, which means the moon will take more time to pass through Earth's dark shadow, making the eclipse last longer.

The longest possible lunar eclipse is 1 hour and 47 minutes, according to EarthSky.

The total eclipse will begin at 7:30 p.m. UTC, and end at 9:13 p.m. UTC. The peak of the eclipse will occur at 8:22 p.m. UTC.

Just a few days after the lunar eclipse, Mars will pass by Earth at its closest point to since 2003. On July 31, the red planet will be only 35.8 million miles away from Earth, making it clearly visible to the naked eye.

Stargazers in the Eastern Hemisphere will easily be able to see both Mars and the blood moon on July 27 and 28.