Blood Moon
The complete April 2014 total lunar eclipse can be seen in this image. In the sequence, the moon enters Earth's partial shadow, darkens and turns red as it enters Earth's shadow. Reuters

Mark your calendars for Sept. 27 and be prepared for a cool celestial event. Supermoons have become events of great interest, even with detractors like astrophysicist Neil deGrasse Tyson who say a supermoon is nothing more than a slightly larger full moon. And the upcoming supermoon holds even more in store because it will coincide with a lunar eclipse, the first since 1982 and just the sixth since 1900.

In some ways, September's supermoon lunar eclipse is like the upcoming "Batman v. Superman: Dawn of Justice": It combines two great things in one event. A supermoon is a full moon that appears slightly larger -- around 14 percent -- and can occur several times a year. The magnification effect is due to the moon reaching perigee -- the point of its orbit where it's closest to Earth -- when it turns full. Tyson is no fan of supermoons and has shared his disdain whenever possible. "July’s full moon is to August's 'Super Moon' what a 16.0-inch pizza is to a 16.1-inch pizza. I’m just saying," Tyson wrote on Twitter after a supermoon in August 2014.

Luckily, September's supermoon will happen during a lunar eclipse, which occurs when the moon passes into Earth's shadow. This creates a red hue and that's why it's sometimes referred to as a blood moon. Earth's atmosphere filters out blue light, and red light passes freely onto the moon. September's supermoon lunar eclipse also will end the lunar tetrad and serve as the harvest moon, according to EarthSky.

The lunar tetrad is a series of four lunar eclipses occurring every six months; the current tetrad began in April 2014. The last lunar eclipse was a relatively short one -- lasting just five minutes -- and rising over the Pacific Ocean in April 2015.

The harvest moon is the full moon closest to the autumnal equinox for the Northern Hemisphere. September's full moon is the first of the spring for the Southern Hemisphere.

Most of the world will be able to view the supermoon lunar eclipse, with the eastern part of North America and all of South America having the best view of the event after sunset Sept. 27. Europe, the Middle East and Africa will be able to view the eclipse in the predawn hours of Sept. 28.