Lunar Eclipse of 9th to 10th January 2001

A Lunar eclipse, like the one that took place on the evening of 9th January, is a slow-moving affair. The Sun is behind the Earth and the Moon is on the other side. Slowly and painfully the full Moon advances into the Earth's shadow, goes into totality and then re-emerges and becomes a resplendent full Moon again. Because we have an atmosphere and because of the finite diameter of the Sun (not a point source of light), the shadow of the Earth is never sharp. Nevertheless you can still make out that our shadow is curved, not a straight edge, particularly if you watch an accelerated animation as I am about to show you below. The Moon entered the umbra (the "solid" shadow of the Earth) at 2242 and left it at 0159 Oman time. So what do you do while you are watching this slow-moving event? Take pictures, of course J But how? Let us start with some key observations:

The photo below, taken while the eclipse was progressing, trying to use a compromise shutter speed, illustrates the problem of exposure:

This photo shows the still sun-lit crescent as way over-exposed but does illustrate the reddish tone of the eclipsed part. The animated gif below is a sequence of photos taken at 15 minute intervals, but the ones during totality have been left out (they appear pitch black). Actually, post-totality there were clouds, and I could not stick exactly to my 15-minute periods but had to make do with whenever the clouds cleared.

Note that the Earth's shadow appears to be off-center, otherwise the Moon would have entered and left it in a symmetric manner. North is at the top and one can see that our shadow is centered somewhere south of the Moon. Also note how huge our shadow is compared to the Moon itself. Exposure for each photo was 1/1000th sec using a Celestron Ultima 2000 8" Schmidt Cassegrain telescope at f/10 (focal length 2030mm). The scope was mounted on an equatorial wedge and tracking at the "Lunar" rate. The gif below shows what happened during totality (each photo had a 4sec exposure):

Note that the glow is lopsided and is moving from top-right to top-left, again because the Moon was not exactly in the center of the Earth's shadow. The glow here is NOT the sunlit crescent. At 1/1000th sec the whole Moon photographs as pitch black.

By the way, the very first photo was taken at 2215, before the eclipse began at 2242. But being so close to an eclipse, the Moon was as fully illuminated as it ever gets from our point of view. You can see an enlarged image of the full Moon, together with the locations of the Apollo landings by clicking here. Other astro stuff below.

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