It's when the moon will begin to enter the outer part of the Earth's shadow, called the penumbra.
In the US, the eclipse will begin relatively early Sunday evening, making it easier for children to stay up and enjoy the show. On Jan. 20, the moon will be about 222,274 miles from Earth as a full moon. First, the moon will be nearly at perigee - or the closest point to Earth in its elliptical orbit. Those combined with the trick of the eye that happens during moonrises that make it already look bigger mean super moon rises are spectacular.
A rare lunar eclipse entitled the "Super Blood Wolf Moon" will appear across the world, including the United States, this Sunday. The partial eclipse is expected to conclude just before midnight.
During a total lunar eclipse, the moon can turn a coppery-reddish colour as Earth's atmosphere scatters the light from the sun, which will lie directly behind it.
"If you only start looking during totality, and the eclipse is a dark one, you may not immediately be able to see the moon, especially if you are viewing from a town or city", a spokesperson said.
The name "wolf moon" comes from the Old Farmer's Almanac to refer to a "full moon".
It's hard to predict the exact hue of lunar eclipses, but whatever shade results can offer insight about the chemistry of the Earth's atmosphere.
Hence, the Super Blood Wolf Moon.
The total phase of the eclipse will be visible from the Western Hemisphere, Europe and the western part of Africa, as well as the northernmost portions of Russian Federation.
Although it is set to be a late Sunday night, there is no shortage of activities inside the centre in the lead-up to the eclipse. In all, assuming good weather conditions, this shady little drama will have a potential viewing audience of some 2.8 billion people.
This is not the first time a total lunar eclipse has coincided with a major Boston sporting event. Sunday's observatory event is all-ages and doors open at 8:30 p.m. Ticket price is by donation only. For a shadow, it will be quite bright: Before a potential audience of almost three billion people, the moon will gradually transform into a glowing copper-colored orb, tinted by sunlight bouncing off and passing through the air in our planet's dense atmosphere. For a brief time on Sunday the entire visible face of the moon will bask in what is literally an out-of-this-world sunset.