SUPER BLOOD MOON TOTAL LUNAR ECLIPSE
BEFORE SUNRISE ON 28 SEPTEMBER
The partial solar eclipse of 13 September which was visible in South Africa but not Tanzania is now followed two weeks later with a total lunar eclipse that will be visible to us before dawn on Monday September 28.
Eclipses are caused by shadows cast when the Sun is lies on an exact straight line with Earth and Moon. During a solar eclipse the Moon is in between so we see its shadow as having eclipsed the Sun. The night side of the Moon is facing us so only during New Moon can we get a solar eclipse.
During this September 13 solar eclipse, the Moon covered only about 42 percent of the Sun when it was viewed at the southernmost tip of Africa during this September 13 eclipse.
During a total solar eclipse the Moon is able to cover the full disc of the Sun because the size of Moon and Sun are almost exactly the same. It is just a coincidence of nature that the angular size of Sun and Moon are exactly the same (1/2 degree) because the Moon is moving ever so slightly away from us every day by about 4 cm per year so at this particular time in the life of our Earth the Moon has exactly the same size as Sun and hence can cover the Sun completely and cause a total solar eclipse.
Having just caused a solar eclipse on 13th September, since the orbits of the solar system lie on a flat plane, the Moon is still is in alignment with Earth and Sun to form an exact straight line which results in a lunar eclipse. Hence lunar eclipses occur two weeks after a solar eclipse during Full Moon with the Earth between the Sun and the Moon, causing the Earth’s shadow to fall directly on to the Moon. The Earth’s large size casts a large shadow three times larger than the size of the moon. Hence lunar eclipses last longer and are seen by everyone who are on the night side when a lunar eclipse occurs.
During this Monday September 28 dawn lunar eclipse, we will be able to see the beginning of the eclipse at 04:07 AM when the Moon will be 30 degrees above the western horizon with the Earth’s shadow edging on to the Moon from its upper right edge. A black shadow will gradually slide over the face of the Moon which will be covered up by 05:11 AM by which time the Moon will be lower in the west, 15 degrees above the horizon.
At 05:47 AM the Moon will be deepest within the Earth’s shadow the Moon darkens to its maximum amount. However by that time the Moon will be very low, only 6 degrees above the west horizon so we may get lucky if there are no horizon clouds. We cannot see any further eclipse beyond that because the Moon will have set below the west horizon and the Sun will have risen to bring in the Monday morning at 6:20 AM. Observers in the west of Tanzania in Kigoma and Bukoba will see a little more of the full eclipse than those in Dar es Salaam and Zanzibar. The whole period of the eclipse, including the invisible penumbral parts, lasts from 03:11 AM to 08:23 AM.
Once the Moon is fully covered after 05:11 AM, the colour of the Moon becomes bright red or brown and is called Blood Moon. The colour arises from the light that is bent or refracted when it passes through the Earth’s atmosphere and blue light is deviated away while only red light remains. This red light that has passed through the Earth’s atmosphere bends into the Earth’s shadow that falls on the Moon, giving it a red colour called the Blood Moon.
The colour of the Moon during a total phase of the eclipse is a good indicator of the pollution in our atmosphere. A clean atmosphere produces brilliant brown or deep orange colours while a polluted atmosphere produces a grey colour. Watch out the colour of the Moon during this eclipse. The Djon scale allows you to give a value to the type of colour of the Moon during the total phase of the lunar eclipse. Zero is assigned to a grey almost invisible Moon while 4 is assigned when the Moon is vivid deep orange or red. Estimate the Djon value when you watch this eclipse and we can collect it for submission to a database.
This Monday’s total lunar eclipse is even more significant because the Moon will appear much lager than normal since it is at its closest point in its orbit around Earth. Such a Moon is called a supermoon so this lunar eclipse is a Super Blood Moon lunar eclipse. The next such occurance will not take place until 2033 so do not miss this one on Monday before sunrise.