Friday, December 2, 2011

"Science of Lunar Eclipse through FAQ & Celestial Beauty of Saturday"

A Week prior to the 10th Dec 2011 Total Lunar Eclipse, AKG is beginning the Lunar Week from Sat ( 03rd Dec) to 10th Dec 2011. 
The Lunar Week's inaugural article is here.I am proud to present this article titled as "Science of Lunar Eclipse through FAQ & Celestial Beauty of Saturday" 

The article focuses on explaining the science of Lunar Eclipse through Frequently Asked Questions I have encountered with written in a simple language to enable the readers to understand it. Also given below are the datas from Eclipse NASA giving insight about the event on 10th Dec 2011 when a Total Lunar Eclipse will be visible. 
The Eclipse is important for me and my hometown as the next eclipse ( Total Lunar) will be visible nearly after 6 years !!! 

So sit back and enjoy and wish you a Happy Lunar Week.


Akshay Deoras

"Science of Lunar Eclipse through FAQ & Celestial Beauty of Saturday"
By Akshay Deoras

The coming Saturday,10th Dec  is going to be a wonderful evening for all the astro lovers! There will be a Total Lunar Eclipse on the evening of Saturday which will be the second one of the year ( After 15th June 2011) when the first total lunar eclipse was seen. 
However, the weather didn't allow any view of the eclipse from Nagpur. 

The Eclipse is going to be visible completely  in East Asia,Australia,New Zealand.In India the moon will rise before the beginning of penumbral eclipse in North East states,East central region,Eastern Jammu and Kashmir. For central India including Nagpur,and the remaining regions the moon will rise in the penumbral eclipse. Penumbral Eclipse happens when the moon enters the penumbra or outer faint shadow of the Earth. As a result the TOTALITY PHASE will be seen by these areas. 
However for much of Africa,Europe the eclipse last stages will be seen and so it will just be restricted to Partial Lunar Eclipse for them. The Eclipse will not be visible in extreme west africa,South America and Antarctica prominently. 

The Details for India

I must say that cities in the entire Seven sister states,West Bengal,Sikkim,Bihar,Jharkhand and some parts of Chattisgarh,Extreme eastern J&K  will have the moon rise before the P1 stage. So they can experience the entire phenomena. 
For Kolkata moon will rise on 10th Dec around 1637hrs (1107UT).

The general timings are - 

P1 = 11:33:32 UT ….. (0503PM IST)…..  Moon enters the penumbra 

U1 = 12:45:42 UT …. (0615PM IST)…..  Moon enters the umbra 

U2 = 14:06:16 UT ….. (0736PM IST) …  TOTAL ECLIPSE BEGINS


U3 = 14:57:24 UT …. (0827PM IST) 
U4 = 16:17:58 UT….. (0948PM IST) … MOON LEAVES UMBRA
P4 = 17:30:00 UT …. (11PM IST) …     ECLIPSE ENDS 


Nagpur Special*

For Nagpur, the moon rise on 10th is at 1723hrs IST (1153hrs UT)
Moon enters the Umbra - 0615PM IST 
Total Eclipse Begins - 0736PM IST
Total Eclipse Ends- 0827PM IST
Partial Eclipse ends - 0948PM IST
Penumbral Eclipse ends- 11PM IST


Apparent View of the Moon and Earth's shadow in Real time at 0802PM IST


At 1133UT, the moon's appearance will start fading slightly which is often not noticed by naked eyes. This happens as less dark shadow of Earth falls on the Moon. As the Moon starts progressing towards the Umbra Region, from 1406UT, the Totality will start and the Moon's surface will begin to cut off due to the earth and moon will start getting darker but there will be appearance of Red shades will increase and at 1432UT the moon will be BRICK RED. The reverse process will again follow as the moon leaves umbra completely at 1618UT. 

The Eclipse will be over at 1730UT! 


The Myth of Eclipses

The phenomena of eclipse wasn't as enjoyable thousands of years ago as it is today especially to see the copper red moon of totality. 

Chinese people had mentioned first about Solar Eclipse long way back around 2134BC. People of the ancient times used to fear from the eclipse as they thought it was a curse. Even the famous war between Lydians and Medes ended after 5 years at once as the day turned dark due to Solar Eclipse- A phenomena which they didn't understand. 

  For those who don't know the science of the eclipse, lets learn it through Frequently Asked Questions (FAQ)
Q.Ingredients for the recipe of Total Lunar Eclipse?

 A. Sun,Earth,Moon

 Lunar Eclipse occurs when the Earth's shadow falls on the moon.When I am standing in front of a tube light my shadow falls behind ( Say there is a screen). This screen is the moon and I am the earth for consideration

Q.How is the moon's orbit around the Earth?

A.The orbit of the moon around the Earth is an ellipse ( curve obtained when you join letter "u" from top with inverted "u"). Moon's orbit around the earth makes an angle of 5 Degree 14 mins with the ecliptic ( Ecliptic plane is the plane in which Earth orbit's the Sun)

Its like when you consider a clock let the minute hand pointing from 9 to 3 be ecliptic. So the second's hand pointing from 10-4 and 8-2 is the moon's orbit around the earth but in the real three dimension of space.

Thus the second's hand crosses the plane two times.At 9'o clock and 3'o clock.The same is the concept of Moon.
Moon's orbit crosses the ecliptic two times during one orbit referred as nodes( Explained below)
Thus for earth's shadow to be casted on moon or moon blocking the solar disc, the moon must be in a common plane with earth and sun i.e have co-planar orbits.

 Q. When Moon crosses the ecliptic twice a month, then why there isn't eclipse twice a month?

      A. Consider the below figure


The Nodal axis is a line joining the two nodes. That is for eclipse moon must be at one node which it does twice in its orbit BUT the sun ALSO must be at the  other far end of the stick ( Nodal axis). It is supposed to happen every 6 months. 

Q. Why doesn't the Eclipse re-occur at the same date after 6 months?

A.The combined gravitational pull between Earth-Moon-Sun creates a wobble in that nodal axis and so it oscillates. Due to this the dates of eclipses aren't repeated at the same dates.


A. When the Totality stage arrives, the moon enters much of the Darker portion ( UMBRA) of earth's shadow. Logically one says that during maximum eclipse, the moon's view must be blocked totally making it dark and invisible for sometime but it doesn't happen. 
It appears Brick or Copper Red ! 
The reason is at this  stage, the sun's light is still traveling in the earth's atmosphere. We know that the WHITE light is composed of seven colors but as per Rayleigh's Scattering, the color having less wavelength will scatter more i.e prominently Violet,Blue and others. Since the Red color has higher wavelength than other colors, its less scattered and so when the sun's light exits the earth's atmosphere the red color spectrum is dominant. This light falls on the moon and we see its reflection. If there is more dust,volcanic ash etc in atmosphere then Moon's color will appear different !  There is a scale known as Danjon Scale which determines the color of moon which will be seen during total lunar eclipse 

The French astronomer Andre-Louis Danjon proposed a useful five point scale for evaluating the visual appearance and brightness of the Moon during total lunar eclipses. 'L' values for various luminosities are defined as follows:

     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.
Courtesy- Arvind Paranjpye

Q.Is Lunar Eclipse SAFE to Watch?

A. Absolutely YES!
Infact I will encourage the readers to hunt with their telescopes or binoculars or simple naked eyes to watch this celestial beauty..

Q.Is Lunar Eclipse connected to any Natural Calamity,disasters etc. 
A. Absolutely not. 

Q.What is the speed of the moon during this projection through Earth's shadow?

A. Around 1.6km/sec 

More questions are welcomed at- 

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