Lunar Eclipse of 2011

We recently witnessed a total Lunar Eclipse, the splendid celestial phenomenon, on 10th of dec 2011 which was second and last such event in the year 2011. The first eclipse happened on June 15, 2011. This time around the Moon had been bigger and redder. A wonder ful video from NASA explains this effect

Couple of interesting facts that I am going to share about Lunar eclispe. We all know that an eclipse has two shadowy regions, Umbra and Penumbra. It is difficult to predict the exact brightness distribution in the umbra so observers use a scale called The Danjon value for estimating brightness at different times during totality of the eclipse.The Danjon scale of Lunar Eclipse brightness was proposed by the French astronomer André-Louis Danjon and is measured on a 5 point scale from L0 to L4, where L is the luminosity.

     L = 0     Very dark eclipse.Moon almost invisible, especially at mid-totality.

     L = 1     Dark Eclipse, gray or brownish in coloration.Details distinguishable only with 

     difficulty.

     L = 2     Deep red or rust-colored eclipse.Very dark central shadow, while outer edge of

     umbra is relatively bright.

     L = 3     Brick-red eclipse.Umbral shadow usually has a bright or yellow rim.

     L = 4     Very bright copper-red or orange eclipse. Umbral shadow has a bluish, very bright

     rim.

At, the time of eclipse, Moon was at an altitude of 30 degrees in the constellation of Taurus and 

was placed in the midst of other recongnizable constellations such as Auriga, Orion and Pleiades.

Eclipses follow a certain periodicity in their occurances. Every year there are at least two lunar 

eclipses. If one knows the date and time of an eclipse, it is possible to predict the occurrence of 

other eclipses using cycle measurements such as the saros. The saros is a period of 223

synodic months (approximately 6585.3213 days, or nearly 18 years 11 days), that can be used 

to predict eclipses of the Sun and Moon. After completing a saros in an eclipse, the Sun, 

Earth, and Moon return to approximately the same relative geometric positions, and a nearly 

identical eclipse will occur in an eclipse cycle. A one half of a saros is called a sar.According to 

NASA, december 10th total lunar eclipse was the 23rd member of Saros 135, a 

series of 71 eclipses occurring in the following order: 9 penumbral, 10 partial, 23 total, 7 partial,

and 22 penumbral lunar eclipses 

Another beautiful and rare celestial effect which was seen during Lunar eclipse is called 

selenelion. This occurs when eclipsed Moon andSun are observed in the sky at the same 

time. 

An active member of Bangalore Astronomy club took brilliant pictures of this eclipse

from Bangalore, India

 Courtesy - KV Shankarnarayanan

Next year in 2012, a total solar eclipse has been predicted to occur on  Nov 13th. 

More information on that later.