- Just before 2 a.m. ET, people will start to see the Earth's shadow crossing the moon
- The moon will turn a copper red for just more than an hour
- There will be four 'blood moons' within a year and a half, and many in the 21st century
- Watch it beginning about 1:58 a.m. ET Tuesday
Tuesday will bring a spectacle in the night sky worth staying up for when the moon turns a burnt reddish orange.
The moon will begin to change color at about 1:58 a.m. ET Tuesday as it starts to slide into the Earth's shadow until it becomes a "blood moon" at 3:07 ET, NASA says. The best part of the show, the total eclipse portion, will last through 4:24 a.m. ET.
The height of the event will take place at 3:45 a.m. ET.
The big problem for potential viewers in the eastern United States will be the cloud cover, which is expected to hide the show from half of the country, save for cities on the coastline, which might be able to peek through.
But cities including Dallas, Denver and Los Angeles should have optimal viewing. NASA said the entire event can be viewed by people in the Americas, while observers in the western Pacific will catch the second half of the event.
The moon will be setting in most of Europe and Africa during the eclipse, so residents there probably won't see much.
This one is just the first in a series of four consecutive total lunar eclipses.
Within a year and a half, North Amerisca will be able to see a blood moon a total of four times. The moon takes on this color during the eclipse as it passes through the Earth's shadow, into which red light from the planet's sunrises and sunsets shines. According to NASA, the exact color depends on what is in the Earth's atmosphere.
The four blood moons will occur in roughly six-month intervals on the following dates: April 15, 2014; October 8, 2014; April 4, 2015, and September 28, 2015.
With that frequency, one might be misled into thinking that they are commonplace.
There are about two lunar eclipses per year, NASA says. Some of them -- penumbral, or barely visible, eclipses -- are so subtle, they go greatly unnoticed.
Other eclipses just cast a partial shadow on the moon but lend it none of that brilliant sunset hue.
Lunar eclipses -- penumbral, partial or umbral -- occur in random order, NASA says. Getting four umbral eclipses in a row is like drawing a rare lunar poker hand of four of a kind.
Just like the poker players, astronomers have a name for that lucky draw. It's called a tetrad, NASA says.
"The most unique thing about the 2014-2015 tetrad is that all of them are visible for all or parts of the USA," longtime NASA eclipse expert Fred Espenak said in a prepared statement.
In the 21st century, there will be many tetrads, but look back a few centuries, and you'll find the opposite phenomenon, Espenak said.
Before the dawn of the 20th century, there was a 300-year period when there were none, he said. Zero.
That would mean that neither Sir Isaac Newton, Mozart, Queen Anne, George Washington, Napoleon, Abraham Lincoln nor their contemporaries ever had a chance to see one.
So, we're in luck.
For gazing geeks, NASA has set up a live web chat to answer questions about the eclipse starting at 1 a.m. ET.
Tuesday's blood moon comes right on time for the Jewish holiday of Passover, which commemorates the ancient Israelites' exodus from slavery in Egypt. According to the Bible, God cast 10 plagues upon the Egyptians, the final plague being the death of the firstborn. The Israelites painted lamb's blood on their doorways so that this plague would pass over their homes.
Timeline of events
12:53 a.m. ET -- The eclipse will officially begin but there will not yet be anything to see with the human eye.
1:40 a.m. ET -- Observers should start to see some partial darkening along the left edge of the moon that will increase as the minutes pass.
1:58 a.m. ET -- Partial eclipse begins: People will start to see the dark disk of the Earth's shadow crossing the moon. The shadow will advanced across the moon throughout the next hour.
2:50 a.m. ET -- As more of the moon becomes covered in shadow, observers should start to see parts of the dark shadow turn dark red or orange.
3:06 a.m. ET -- Total eclipse begins with the moon completely in the shadow of the Earth and should appear reddish orange. The blood moon has arrived.
3:45 a.m. ET -- Great eclipse: The middle of the total eclipse; moon should appear dark red/orange
4:24 a.m. ET -- Totoal eclipse ends: Moon will begin to reappear from the shadow and coloration will begin to disappear.
4:45 a.m. ET - As more of the moon emerges from the shadow, the color should be mostly gone. What is left will appear black.
5:33 a.m. ET -- Partial eclipse ends as dark shadow completely leaves the moon, which will return to its normal look over the next 10-20 minutes.
6:37 a.m. ET -- Eclipse officially ends.