Lunar eclipse over Tonga on 21-22 December [1]
Thursday, December 16, 2010 - 09:49. Updated on Monday, September 9, 2013 - 18:40.
LUNAR eclipses, when the full moon is obscured because it passes through the shadow cone of the earth, are not that rare, although sometimes a few years may pass before one is visible again at a particular location. This year Tonga is quite good off. We had an eclipse on 2627 June, we shall have another one during the night of 2122 December. But for the rest these two eclipses differ from each other as much it can be.
The June event was a partial eclipse, at no instant it became completely dark. As the moon was practically straight above your head (Tonga was really in the center of the visibility area), you even may not have noticed anything unless you strained your neck looking up. Furthermore it happened around midnight and loose clouds came over, I wonder how many people really went outside to see it (at least one).
The coming eclipse will be total. For more than an hour it will be as dark as a moonless night. It will happen early in the night, with the moon still low above the horizon. Shortly if weather permits, it will be a much more awesome sight.
On 21 December the sun sets at 19:16 and at the same time the moon rises in the east-north-east. Strictly speaking at that time the eclipse is already underway, but that refers to the so called penumbral phase, which in practice is not visible. The first bite by the umbral earth shadow in lower right side of the disk of the full moon will take place at 19:33. By then it is still in the middle of twilight and the moon will only be 3.4° above the horizon. Indeed an unobstructed view of the eastern horizon will be needed. Slowly the shadow will progress over the moon until by 20:40 it has completely blotted out the light of the moon. It then will be night with the stars shining and the probably red glowing disk of the moon 16° above the horizon. By then it should not be so difficult anymore to find a location with an open view towards the east.
The moon will remain completely in the shadow for more than an hour, until 21:54, after which the umbral shadow will retreat to the top left, releasing the moon at 23:01. Then the moon will stand brightly in the sky again as full moons tend to do, and all the stars which were so nicely visible during the eclipse will be completely blotted out by its light. Only the brightest stars may still be visible. The moon will be standing in the centre of the winter hexagon (so called because 6 bright stars form a hexagon, which is visible in this time of the year, when it is winter in the northern hemisphere). Can you find them all?
Another total lunar eclipse, much like this one, will occur in the night of 1011 December 2011, but this one will be in the late night and early morning hours, thus not so convenient as this one. On the other hand, the 45 June 2012 eclipse, the next eclipse visible in Tonga after that, will be almost as its predecessor 2 years before that. Tonga in the middle of the visibility, meaning an eclipse at midnight straight above your head, but again partial only and even a little bit smaller as well. Not until 2014 and 2015 before Tonga will be almost centered once more to receive a total lunar eclipse, three times in a sequence! Firitia Velt, Fasi mo e afi.