Sunday, June 19, 2011

Total Lunar Eclipse in Retrospect

Despair and Delight

This is a logical corollary to my last blog post heralding the total lunar eclipse of June 15-16.  I had ended it with the fond hope that the prevailing cloudy monsoon skies all over south India would relent and provide a special window to view the event.  However, the weather continued to deteriorate and at around 4 PM on 15th June I sent out the following message of despair to many fellow eclipse chasers; "The weather in Mysore right now is so terrible and the prospect of any degree of clear skies tonight so remote that my promised next blog post may well have to carry the caption 'Episode of the Invisible Eclipse!'".  Would anybody believe that my next message to the same group of people on the following morning, after the eclipse, read; "We had a totally surprising and unexpected break in weather after around 11 PM yesternight.  This enabled the diehards among us to stay awake all through the night and see a wonderfully memorable eclipse."  I have rarely experienced such a magical transformation in nature from one extreme to another.  In response, there was a matching transformation of human emotions from despair to delight.  I recall a very similar experience with the total solar eclipse of 22 July 2009 which I had watched with similar feelings from a hilly place near Anji city in far way China (See my blog post titled "The Great Total Solar Eclipse of 22 July 2009 from China").  What a coincidence! When I mentioned this to a friend he told me that this must have been in answer to my silent prayers!  I am glad he didn't label it as divine intervention.

Around 10 PM that day the sky was so densely clouded over that I wouldn't have known where the Moon was and indeed needed to open the Google Sky Map application in my smart phone to find out.  As I was preparing to abandon my plans for the night and go to bed sooner than normal, my constant companion Chiranjeevi excitedly barged into my home around 11 PM and literally dragged me outside to show me the sky, now punctuated by a mockingly bright full Moon, surrounded by thin and swiftly parting clouds. We couldn't believe this incredible luck and quickly got back on track with our plans.  With a lingering suspicion of the weather, I opted to follow the unfolding events from the comfort of my home while the more adventurous Chiranjeevi opted to move out to a spot on the outskirts of the city some 15 km away with another friend Mr Krishnamurthy.  He took with him my Canon 350D SLR camera and an excellent 70mm spotting telescope. We kept in constant communication with each other throughout the night.  A number of other enthusiasts, who would otherwise have joined us, had apparently given up and retired to bed in blissful ignorance of the changed circumstances.

Progress of the Eclipse 

I set up shop on the roof of my two storey house, equipped with a 90mm Maksutov-Cassegrain Sky-Watcher telescope, an excellent Olympus 10x50 binoculars and my trusted high zoom Lumix digital camera mounted on a sturdy tripod.  A good measure of light pollution was provided by two nearby street lights that have always been a constant source of annoyance for me.  This didn't matter at all against the bright background of moonlight early on, but as totality approached I regretted not joining my two colleagues who had positioned themselves well away from disturbing lights somewhere on the outskirts of the city. 

As expected, the penumbral phase of the eclipse was hardly noticeable even as the Moon played hide and seek through thin layers of bright clouds.  Saturn and some of the brighter stars could be seen but the fainter stars were difficult to make out.  The interplay with the clouds continued into the early partial umbral phase of the eclipse. Thereafter, crystal clear skies set in and lasted well into the total phase.   The following images taken by me with my Lumix camera show the lunar surface before the eclipse and at different times during the progress of the partial phase from the eastern limb of the moon to its western limb right up to the onset of the total phase:

Disappearing Act

As expected, at any given time the eastern part of the lunar surface which was immersed in the umbral shadow continued to be visible, but very dimly, with a faint reddish hue.  The brightly lit western portion continued to be seen as brightly as before.  As the terminator, which is the curve demarkating the two portions, progressed westward, the overall brightness decreased rapidly and the night sky as a whole grew darker.  In this process, as Chiranjeevi later remarked, one could view in a short period of just about an hour the entire sequence of phases marking the waning of a full moon to a new moon over a two week long period of time.

When the totality set in, the last vestiges of the brightly lit part of the moon disappeared, the sky became almost, but not quite, as dark as on a moonless night and the western part of the now fully eclipsed moon could be seen distinctly brighter than the eastern part.  It may sound odd to talk about seeing a fully eclipsed moon, but I have already explained how this is possible due to the scattering of sunlight by the earth's atmosphere.  As the total phase of the eclipse progressed the western portion grew darker.  Eventually, at the midpoint of the total phase at around 1.40 AM, the lunar surface became uniformly illuminated with a very dark reddish hue - apparently much darker than what had been expected.   On the Danjon Scale of Lunar Eclipse Brightness, I would easily assign zero to the L value. When this happened, it was extremely difficult for me to spot the Moon with the naked eye but there was no difficulty doing so with the binoculars and the telescope.  However, Chiranjeevi and Krishnamurthy reported that they were able to spot the moon even during this time as they were placed well away from disturbing lights.  It was exhilerating to look through the telescope frequently and catch the moon in its changing phases, especially at totality, with a field of view encompassing the whole of the lunar disk.

The following two pictures taken by Chiranjeevi during the long period of totality are indicative of the wonderful sight of the total eclipse when the Moon appeared like a friendly ghost suspended in the sky, peeking back at the viewer.  The first picture was taken at ISO 1600 with a 10 sec exposure at f/6.3 on the Canon DSLR camera.  The two small streaks at lower right are star tracks.  The second picture shows the faint Milky Way patches and numerous stars, particularly in the Scorpius and Sagittarius constellations. The traditional shapes of these two constellations can be easily made out in the picture. It also shows traces of scattered green light from a laser pointer, including the light close to the pointer itself at extreme lower right. This picture was taken at ISO 1600 with a 30 sec exposure at f/4, also on the Canon camera.

The Net is flooded with pictures of this type from different parts of the world.  One of the best I liked was a spectacular stacked picture of the eclipsed moon with the surrounding star fields and the Milky Way patches. The reader will find it at:

By now I had to give up any further attempts at photography since the long exposure times required a tracking telescope and my Meade 127mm Maksutov-Cassegrain has been under repair for sometime now. I thought I had actually lost the Moon, even through the binoculars, for about 10 minutes, but this could well have been due to a thin layer of haze covering the sky at that time.  Thereafter, there was a period of about 10 minutes when the sky became so clear that I could even see the patches of the Milky Way in Sagittarius from my light polluted location.  My colleagues reported that they were able to do this over a much longer period of time and more clearly as well.  Nowadays it is becoming virtually impossible to do this in the highly light polluted city skies, including Mysore.

Reappearing Act

By 2.30 AM the eastern portion of the lunar surface which was significantly brighter than the other part, came alive with a sliver of it showing through in bright light.  This marked the end of the total phase.  Thereafter, the brightly lit porttion started growing in size even as the other side grew markedly fainter.  It was like the mirror image of the events seen earlier leading up to the immersion of the moon into the umbral shadow.  After watching this for the next twenty minutes or so I decided to call it a day, not waiting to see the full moon in all its recovered glory.  My colleagues however stuck it out till the very end.

Media focus

Unlike total solar eclipses when the populist media goes into a frenzy with dark forebodings, the media glare during this eclipse was quite subdued and largely positive.  While the national level TV and print media gave generally accurate coverage both before and after the event, local media went about in their usual ways.  Astrologers and soothsayers had their usual say, with detailed prescriptions on how to protect oneself from or ward off the evil effects. 

Here are two samples of what was intended as some enlightened reporting: (i) The unusually long lunar eclipse, according to the astrologists, will have a negative effect on some zodiac signs, while it will benefit others; (ii) Natural calamities will affect the routine life of the countrymen, said astrologists when asked about the possible impact of this lunar eclipse on human lives.

I was interviewed by a Kannada TV channel on some technical aspects of the eclipse.  Among other things, the interviewer had pointedly asked me if there was any special type of radiation emitted during eclipses which would be harmful to people.  My responses in a two-minute video recording at home were whittled down to just twenty seconds in its actual news coverage of the day.  My obvious answer to the above question had been edited out.  To any viewer I must have appeared to be speaking irrelevantly.  This was followed by an equally short 'astrological evaluation' of the event by an appropriately attired astrologer who said something about the 'gravitational influence' of the event on people (no such influence exists), but otherwise mercifully refrained from predicting any grave consequences. 

A widely circulated Kannada newspaper gave equal space, side by side, to both the astronomical and astrological aspects of the impending eclipse.  I view this as a victory of sorts for science since the same newspaper had given three times as much space for the astrological aspects in its coverage of the great annular solar eclipse of 15 January last year (See my blog post titled: "Ring of Fire – The Great Annular Solar Eclipse of 15 Jan 10").  The astrological prescriptions this time included: (i) Performance of a 'Shanti' (penance) by people of just two 'rashis' who would be grossly affected by the eclipse (how considerate in excluding the vast majority of humans!), (ii) A much milder atonement by people of four other less severely affected 'rashis' by repeatedly chanting an exquisite sanskrit shloka invoking the mercy of the heavens during the eclipse (It didn't say how many times, but I believe the prevailing norm is one thousand), (iii) Abstaining from eating anything from as early as 12.30 afternoon on the 15th till the termination of the eclipse the following morning (One should welcome this strongly at least on health grounds), and (iv) Total exemption from fasting for children, the aged, the infirm and pregnant women (Again, how considerate, but how can one differentiate if birth dates and times are the sole criteria?).  In addition to these, there was of course the ever implicit warning, very often explicit as well, that it would be harmful to view any eclipse in any manner anytime!


The eclipse appears to have been a near total wash out in several places in the south, including Bangalore.  During the total phase I got a phone call from a friend in Mangalore requesting help to locate the (fully eclipsed) Moon in what appeared to be reasonably clear skies there after a bout of rain earlier.  After some effort she did indeed manage to see the moon and thanked me profusely for the assistance.  The following day I got several calls and messages from friends who had managed to watch the eclipse successfully, particularly in Mysore which seems to have been specially favored by nature.  Incidentally, normal monsoon service was restored within minutes of the end of the eclipse. 

Dr S V Narasimhan of Virjapet, Coorg wrote that his motivation had been reinforced to such a degree that he spent the whole night peeping through thick monsoon clouds, getting occasional glimpses of the moon.  I wonder how many other people did so, even in cloudless skies. Since the event lasted such a long time, unlike a total solar eclipse, he would not have missed any of the important phases of the eclipse.  I am glad I have such good reason to mention him here as prominently as in my previous eclipse related blog posts.

Even in places where the eclipse may have been clearly visible, many inquisitive people may have been discouraged by the late hour of it. Those who missed it do not have to wait too long for the next such opportunity.  The next total lunar eclipse is due on 10th December this year and will again be visible all over the country, soon after sunset.  A great many more people should be able to see it for two reasons - very high probability of clear skies and the total phase occurring between 7:36 PM and 8:27 PM which is well before dinner time for most of them.  Of course there are lots of people who may refrain from seeing it even at such an opportune time.  The media can do a great deal to educate them, at the very least by not giving undue publicity to blind beliefs and superstitions. 

Friday, June 10, 2011

Watch out! - Total Lunar Eclipse on 15-16 June 2011


Three of my earlier blog posts related to my personal experience of witnessing three great solar eclipses from widely different locations, both within and outside the country, over a span of three decades.  Though I have seen a fair number of lunar eclipses, the only reaon I have not written about any of them is that none of them is etched in my memory as strongly as the three solar eclipses did.  This time though, I am writing about a total lunar eclipse which is slated to happen in the immediate future, on the night of 15-16 this month (June 2011).  I am doing this by way of advance information to alert interested readers and invite them to share my experience if the rather unpromising monsoon skies permit viewers in any part of the country.

How Eclipses occur

As pointed out in an earlier post, solar and lunar eclipses as seen from the Earth would not have been possible at all but for a very fortuitous and remarkable circumstance relating to the three celestial bodies. The apparent sizes of the Sun and the Moon as seen by us on Earth just happen to be nearly the same, approximately half a degree in angular diameter. Let me first repeat my earlier explanation in lay terms of how lunar eclipses are caused.  At predictable times during the motion of the Moon around the Earth and of the two together around the Sun, the three objects can be found in a straight line for short durations of time. When the Earth comes between the Sun and the Moon as on a full moon day, the latter can be found in the shadow of the Earth and hence sunlight will not be falling on it directly.  This is when a lunar eclipse occurs.  As seen from any point on the Earth, the eclipse may be partial or total.  One might expect the Moon to be completely hidden from view during a total lunar eclipse.  However, the whole of the Moon can be seen clearly as a faint coppery red object because of sunlight scattered by the Earth’s atmosphere, predominantly in the red, falling on the lunar surface and thereby illuminating it.  It is a wonderfully beautiful sight to behold! Would it be fair to regard the Moon as truly eclipsed?

In contrast, when a total solar eclipse occurs, the Sun's disk is indeed fully hidden by the Moon for the duration of totality.  The spectacular sight we see then is that of the glowing solar corona, not of the Sun itself.

Total solar eclipses are relatively rare events; exceptionally rare from any specific location on Earth.  One may end up waiting a whole lifetime for it to be visible from ones' own backyard.  Also, the total phase lasts typically just a few minutes, the longest possible duration being about 7.5 minutes.  In contrast, total lunar eclipses are more frequent, visible over a very large area of the Earth's surface and with much longer duration of totality.   The reason is easy to understand.  The Earth is about eighty times as large as the Moon and hence the area of its umbral shadow at the Moon is very large, much larger than the visible surface of the Moon.  In contrast, the umbral shadow of the Moon at the Earth during a solar eclipse is only a small fraction of the visible surface of the Earth itself.

The following diagram shows how a lunar eclipse takes place.  Visualize the situation when the locations of the Earth and Moon are interchanged to depict a solar eclipse.

Forthcoming Eclipse of the Moon

The forthcoming total lunar eclipse of Jun 15-16 will occur when the Moon is situated in the southern constellation of Ophiuchus as shown misspelt in the following chart generated with the Starry Night Pro Plus 6 astronomy software package.

[Click to enlarge]

Apart from the constellation Ophiuchus, which is traditionally not regarded as a zodiacal constellation, the chart also shows the two neighbouring and very prominent southern  zodiacal constellations Scorpius and Sagittarius. The Moon passes well within the Earth's umbral shadow during a total phase lasting about 100 minutes, one of the longest in recent decades.  The Moon's contact times with the Earth's umbral and penumbral shadows are shown in the following figure adapted from the NASA ecipse website.  The times shown are in Universal Time (UT).  Add 5:30 to obtain the local time (IST) anywhere in India.  Thus, the onset of totality will start at approximately 11:52 PM on the night of June 15 and end a little after 3:02 AM on the morning of June 16.

Watching the Eclipse

Sunset on 15th eveneing should be greeted by a bright and brilliant full Moon growing more and more prominent in the sky as the night progresses.  As the path of the Moon enters the Earth's penumbral shadow around 10:54 PM it may be extremely difficult to notice even a slight decrease in the brightness of the Moon.  Only skilled observers may detect a faint shading across the lunar disk. This phase will last about an hour until the Moon starts entering the umbral shadow of the Earth around 11:52 PM.  This marks the beginning  of the partial phase of the eclipse.  Thereafter one should be able to see a progressive 'eating away' of the Moon's surface and a marked decline in brighness as the visible portion of the lunar surface reduces.  Around 00:52 AM on June 16, totality will set in when the whole of the lunar surface is inside the Earth's umbral shadow.  However, as already explained, the Moon continues to be visible as a faint copper red disk.  This phase lasts the next 100 minutes, with small but noticeable variations in the overall brighness.  This is the time when the viewer can soak in a wonderful view of the night sky with a faint reddish full Moon appearing to be suspended like a friendly ghost in the sky with rich star fields nearby.

The eclipse will be seen in a part of the southern sky which is very rich in stars, star clusters, nebulae and the densest part of our Milky Way galaxy.  Scorpius and Sagittarius are two of the most prominent and easy to identify constellations in the night sky. If the visibility is good, the patches of the Milky way shown in the above chart should be seen clearly during the total phase of the eclipse.

The total phase will end by 02:32 AM when the Moon should begin to shine in direct sunlight.  It should progressively grow brighter and restored very nearly to its full glory when the partial phase ends around 03:32 AM.  However, the Moon will remain in the penumbral shadow until around 04:30 AM.  This marks the end of what should be a memorable lunar eclipse.
Unlike a total solar eclipse, one need not be in any hurry to watch the lunar eclipse because of its very long duration.  While watching it, the reader is urged to explore the rich southern sky and try to locate most of the Messier and other stellar objects in Sagittarius and Scorpius, particularly the patches of the Milky Way in the direction pointing to the galactic centre in the former.  A pair of binocualrs would be the best means to do this and it can be used for a blown up view of the eclipsed Moon as well.  Unlike a solar eclipse where one has to take special precautions and safe filters to view the event, the Moon is a totally harmless object at any time, and especially so during an eclipse, no matter what the media may project.  The astrologers and soothsayers will no doubt have their field day with a highly gullible public willing to believe anything portentious and sensational and not caring for a scientific perspective of the event.

Eclipse Visibility

The following illustration, also from the NASA website,  shows the visibility of the eclipse from any place on the Earth.  As is evident, the event can be seen in its totality from most parts of Asia and Africa as well as many other regions.  For a solar eclipse one would have to show a narrow visibility band on a map of a small part of the Earth's surface (See my previous blog posts on solar eclipses).  Also, the contact times would be significantly different for different locations on the Earth, both inside and outside the totality band.  In contrast, one set of contact times will be sufficient for all observers of a lunar eclipse.

Dr Fred Espenk, popularly known as "Mr Eclipse" for his pioneering work on eclipses, recalls having seen thirty years ago a total lunar eclipse with the Moon located very nearly in the same part of the sky as the one expected on June 15 this year. He was "amazed at how brilliantly the summer Milky Way glowed since it was all but invisible during the partial phases." Observers will have a similar opportunity during the forthcoming eclipse. In this case, the totally eclipsed Moon will lie just 8° northwest of the brightest Sagittarian star clouds.

Here is a picture of the totally eclipsed Moon taken during an earlier occasion.

During the ensuing eclipse, as in the above picture, the northern regions of the Moon will probably appear brighter than the southern regions that lie deeper in the umbral shadow. Overall, the surface may appear darker than during a typical eclipse of this type. Since the Moon goes through a large range of umbral depths during totality, its appearance may change significantly with time. It is difficult to predict the exact brightness distribution in the umbra, so observers are encouraged to make their own comparative visual estimates at different times during totality using what is known as the Danjon Scale of Lunar Eclipse Brightness. Please refer to the NASA eclipse website for details.

The follwoing is a composite image of the Moon depicting its different phases during an earlier eclipse:

Photography of the lunar eclipse is relatively easy, especially during the partial phases.  Because of the long duration of totality, one can expect to capture excellent pictures after some initial trial and error with a good digital camera at high zoom levels.  Mounting the camera on a rigid tripod is strongly advised.


It is hoped that the prevailing cloudy monsoon weather will relent and provide a clear sky to view the special event on the night of June 15-16 everywhere within the country, particularly the southern region where the probability of clear skies may be rather discouragingly low.  I would love to hear from successful viewers by way of observations and comments posted here or mailed to me directly.  I will try to correlate these with my own observations and report in a later post before the end of the month.