By Lauren Casey

PHILADELPHIA (CBS) — In the wee hours of Friday morning, an eerie astronomical sight will appear in the sky. A partial lunar eclipse will be visible to stargazers across a large portion of the planet, including the Delaware Valley.

The eclipse will commence when the moon first slips into the earth’s less opaque, outer shadow called the penumbra at 1:02 a.m. Friday to result in a dimming effect on the moon. This happens as sunlight which would otherwise reflect off the moon to illuminate the stellar orb is blocked.

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Credit: CBS3

The pièce de résistance takes place between 2:18 a.m. and 5:47 a.m. when the moon slowly passes through the earth’s dark, innermost shadow, the umbra — Latin for “shadow” — and takes on a spooky reddish or coppery hue.

At six hours and two minutes, the total duration of the eclipse, from the moment the moon enters earth’s penumbral shadow to the moment it exits, will be the longest since the year 1440.

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The last time a partial lunar eclipse endured for as long was in the year 1440, about the same time the Incas were erecting Machu Picchu.

The timing of the eclipse comes as the moon closes in on apogee or its farthest point from the earth for the month. This is the cause of the extended duration. The farther away from the moon, the slower it cruises along its orbit, and thus the moon will require a bit more time to slide out of the earth’s shadow.

The maximum eclipse will occur at 4:02 a.m. during which up to 99.1% of the moon will be engulfed by the umbra. For maximum viewing pleasure, the best time to take a peek will be between 3:30 a.m. EST and 4:30 a.m. EST.

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So set your alarm and have a gaze at this rare, celestial delight.