The first night of Passover begins at sundown and will coincide with the first of four rare total lunar eclipses in row.
Passover, an eight-day festival commemorating the release of the Jews from slavery in Egypt, is celebrated on the first two nights with a meal called the seder.
Focal points of the seder include eating bitter herbs to commemorate the bitterness of slavery, drinking four cups of wine or grape juice to celebrate freedom and recitation of the Haggadah, a liturgy that describes the story of the Exodus from Egypt.
During the eight days of passover, Jews refrain from eating leavened bread, replacing it with matzoh to commemorate the unleavened bread the Israelites ate in their hurried flight from Egypt.
The lunar eclipse, which will be visible across the Western Hemisphere, will begin at 2 a.m. with the total phase lasting 78 minutes, starting at 3:06 a.m. Philadelphia time and ending at 4:24 a.m.
Even though the moon is in the Earth's shadow, it should appear a bit colorful, some shade of red or orange. That's from light around the edges of the Earth - essentially sunrises and sunsets - splashing on the lunar surface and faintly lighting up the moon, said Alan MacRobert, senior editor at Sky & Telescope magazine.
The dates for the next three total eclipses are Oct. 8, April 4, 2015 (also the first night of Passover), and Sept. 28, 2015. The last time four total lunar eclipses occurred in a row - called a tetrad - was in 2003-2004, and there will be seven more this century.
Some see the four lunar eclipses, including two that coincide with the start of Passover, as possibly signaling the fulfillment of end times prophecies, but many others reject that. As a headline at Space.com says, a tetrad is "not a sign of apocalypse."