By Firitia

When the full moon rises on the evening of Tuesday 15 April at 18:24, a lunar eclipse will be already in progress.

However, the first and last stages of any lunar eclipse take place in the penumbra or half-shadow of the earth and are always inconspicuous, so not much will be lost by not seeing it.

Things are getting more interesting when the moon enters the umbra or core-shadow of the earth at 18:58. By then twilight is almost over and the moon will be a hand-width (7°) above the eastern horizon, having cleared most obstructions.

Slowly, a dark shadow will bite away more and more of the moon, starting from the underside. This process will continue until the whole moon has been obscured by 20:07. Then for 78 minutes the moon will completely remain inside the shadow of the earth; dark and deprived of sunlight. But because of the earth's atmosphere, some sunlight trickles along the rim of the earth towards the moon. But it is only the red light, and for the same reason that the sun looks weak and red when on the horizon.

As such, the moon in a lunar eclipse usually does not completely disappear from view but remains visible as a faint, red disk. Nevertheless, the night will be as dark as any moonless night with all the stars brilliantly visible.

Spica

At the midpoint of the eclipse at 20:46, the moon will be 32° above the horizon. A finger-width (3°) away from it at upper-right shines the bright star Spica. A hand-width (9°) to the upper-left you can see the red planet Mars. Saturn is on the other side, but more than twice as far from the moon, and possibly still too low above the horizon to be seen.

While talking about planets, one more planet is visible: Jupiter. About same height as the moon, but in the northwest; the brightest object in the sky. There are also two planetoids close to the moon, Ceres and Vesta, but they are faint, you need a star-map to identify them.

By 21:25 the moon will break loose from the umbra. Suddenly light returns to the upper-left side of the moon, spreading until by 22:33 the partial eclipse is over. Once more it will be a moonlighted night with the stars barely visible.

If you miss this eclipse, maybe because it is clouded, there will be another chance on 8-9 October 2014 and also on 4-5 April 2015, but those will be smaller and not so conveniently early in the night.

Firitia, is an astronomer and science lecturer who lives at Fasi & Afi in Nuku‘alofa, Tonga.