Sunday, June 10, 2012

Transit of Venus in Retrospect – The lost chance to see at home

The big build-up

The Transit of Venus that happened on 5/6 earlier this month had been justifiably billed as one of the most significant astronomical events of our time, especially from the popular perspective.  Here was something that would not be seen again for well over a hundred years, truly a chance of a life time.  As an exceptionally rare event and of great historical importance as well, it attracted the attention of professionals and amateurs alike, the former for its appeal as a visual spectacle and the latter for its potential as a testing ground for some of the most refined experimental techniques that have a bearing on our search for habitable planets outside the solar system.  It had received a great deal of publicity from both the printed and electronic media, most of it highlighting its scientific aspects.  Astrologers who generally have a field day with their dire predictions when eclipses occur were conspicuously and mercifully silent, though the event was not too different from an eclipse and involved objects all too familiar to their profession.  There were no special poojas in temples to ward off any evil effects of the event, apparently because none were perceived.  Unlike eclipses, planetary transits apparently don’t qualify as harbingers of evil.
In many parts of the world, particularly in regions like southern India, cloudy skies posed a significant threat to the visibility of the event, though even a short respite from the clouds would provide a representative and adequate sample of the long drawn out event.  The pre-event weather outlook promised as much, with bright sunny mornings preceding the D-day, particularly at home in Mysore.  For this reason I had opted to observe the event from the comfort of my home in my home town.

The huge let-down

What transpired on D-day was one of the most disappointing experiences I have ever had in my long tryst with observable astronomical events. With assistance from my grandson, I had set up all necessary equipment at my command and woke up long before sunrise to watch the live webcast of the event in different parts of the world even as I waited for the Sun to rise and show up its face.  I and a small band of highly motivated and enthusiastic friends had to wait a very long time before we could even determine where exactly it was.  Finally, more than two hours after it had been expected to rise, we got our first glimpse of the Sun through a shroud of dense clouds.  The following is the first and only picture of the event I was able to capture at this time with a new Canon PowerShot SX40 HS super-zoom (35x optical) camera, equipped with an appropriate solar filter.

The silhouette of planet Venus against the spectacular backdrop of the dazzling solar disk is seen sharply and unmistakably, though none of the sunspots are noticeable.  The transit was already two-thirds of the way through, having begun around 3:40 AM.  This fleeting glimpse of the Sun lasted only a few seconds, but long enough for everyone in the gathering to be convinced that Venus was indeed in transit across the face of the Sun.  After that, for the next ninety minutes or so, the Sun was playing hide and seek with us, mostly hide because we couldn’t see it clearly enough through our imaging devices or capture it with the camera.

The small mercies

The weather relented to some extent during the final 30 minutes of the event though we never really saw the Sun against a totally cloudless backdrop.  The following set of four pictures shows whatever I could salvage out of the gloomy situation, the last one possible just minutes before the end of transit.  A keen eye can spot some of the larger sunspots if the picture is magnified by clicking on it and opening it in a separate window.

To highlight the effect of the cloudiness, I am reproducing here the following picture taken on the previous evening in much better conditions, showing a number of sunspots quite prominently.  The size of the spot corresponding to Venus in transit was much bigger than the biggest of these.

In Bangalore, where the initial conditions were no better than in Mysore, the situation improved greatly as morning progressed, and the overall conditions were significantly better.  The following set of pictures taken by my son-in-law there with a high-zoom (18x optical) Panasonic Lumix DMC FZ-35 camera compliment my efforts in Mysore and fill the gap as well to some extent.  When magnified, these pictures show the sunspots much better than the Mysore pictures.

Media Glare

The event was shown from beginning to end from various vantage points in the world through live webcasts.  Many TV channels pitched in, sandwiching live pictures and commentaries with their regular programmes.

International Coverage

Perhaps the best live webcast was provided by NASA through its NASA EDGE@Mauna Kea website located at the top of mount Mauna Kea in Hawaii.  Pictures of the event were provided continuously from three dedicated solar telescopes capturing images in white light as well as two different wavelengths – with a Calcium K filter at 393 nm (blue) wavelength and a hydrogen alpha filter at 656 nm (red) wavelength.  Expert commentaries, interviews, and multimedia programmes relating to the event were interspersed with the show in rich abundance.  It attracted a huge international viewership, reaching a peak of about three million at one point in time.  Here are a set of illustrative pictures I grabbed from this webcast (the times are in IST).  It is interesting to see that the sunspots show up best in white light.

The Hawaii efforts were complemented by a worldwide network of about a dozen websites that included one belonging to the Indian Institute of Astrophysics at Hanle in Himalayan Ladakh, the world’s highest astronomical observatory.  Unfortunately, the weather here was a total washout.

When I looked at the IAO Hanle webcast just before sunrise, viewers were being greeted with the following message (presented exactly as seen) repeatedly splashed on the screen: “Live stream from Hanle at a hight of 14800 ft from sea level.  Weather Update:- Its cloudy right now. hope the weather improved by the time the sun rises”.  Not only did they have nothing to show, but also they chose to say so in embarrassingly poor English.

Interestingly, one of the websites was located in St Michael’s Church, Much Hoole, Horrocks in England, home of the historic and pioneering effort of observing the 4 Dec 1639 Transit of Venus by the youthful British astronomer Jeremiah Horrocks (see my previous blog post).
National Coverage

One Hindi news channel chose to give uninterrupted coverage to the event for a considerable time and its excellent work was marred only by the totally irrelevant and meaningless presence of an astrologer in the discussion panel.  It is astonishing how the media in the country try to mix up the irrational with the rational, inviting self-proclaimed pseudo experts to interfere in matters that have nothing to do with them.  This man, in traditional attire and looking like the personification of arrogance, was saying that the event was something well known to ancient Indian scholars who had predicted them much before western civilization woke up to it.  When one of the panelists intervened to point out that even a scientific understanding of the event was of recent origin and asked him to cite specific details in support of his claim, the astrologer contemptuously brushed him aside and instead challenged the panelist to prove him wrong!
Planetariums in several Indian cities played a key role in promoting popular interest in the event, mainly through live telescopic shows, the best way perhaps to leave a lasting impression in the minds of the viewers.  The excitement in school children was particularly palpable.  Media coverage of the efforts of the planetarium in Delhi, where the event was hardly affected by the weather, was noteworthy. This was also the case with the Bangalore planetarium though it was plagued by bad weather for a considerable time initially.

While appreciating the work of such agencies in promoting a scientific temper, one writer writing in the online edition of the Times of India went ethereal by asking, “Can one truly disengage the scientific wonder from its astrological significance?”  He also went off his rocker by claiming “Even a mere transit is believed to have an astrological impact for as many as six months after the occurrence.”  Two other pieces of absolute gems from him: “There are those who believe that this event is leading up to the Mayans’ prediction that the world will come to an end in December 2012”  and The energy of this eclipse also provides with the ability to bring balance within our relationships as well.”  He could well have been a worthy substitute for the astrologer in the TV panel mentioned earlier!

Path of Venus in Transit – Confusing Perspectives

Now it is time for me to try to clear up a major confusion created in the minds of some uninitiated but highly inquisitive viewers.  Echoing their concerns, my long-standing friend Dr Narasimhan of Virajpet had commented in my previous blog post, “I have been following the various articles on ToV on 5-6 June 2012.  But I see the Venus crossing the Sun transversely from left to right, an essential view from high northern latitudes!  But in places nearer the Equator, Venus crosses the Sun vertically from below upwards.  Don't the readers in India, especially southern India, get confused?”  In saying so he had been partly misled by a well-known Astronomy simulation software package (Starry Night Pro Plus) which showed widely different views for different observers by employing differing orientations of the ecliptic (the apparent path of the Earth in orbit around the Sun) in its default settings.  Without pausing to understand what he was really trying to communicate, I had replied hastily but correctly, “There cannot be any confusion since the path of the planet across the solar disk is practically the same for all observers as can be inferred from the graphics provided by Espenak/NASA and reproduced in my article.  Extremely small differences can indeed be seen by different observers in different locations due to the well-known parallax effect, but these are far too small to be noticed by mere visual observations…”  Dr Narasimhan was of course implying something very different.

It was only after I myself had seen the live webcast and telecast pictures of Venus in transit from a number of different sources did I appreciate how pertinent Dr Narasimhan’s concerns were.  As he had anticipated, most viewers must have been greatly puzzled and confused by the widely, perhaps even wildly, differing paths of Venus they saw across the Sun’s face on the TV or monitor screen.  Without trying to justify the confusion, I would like to point out that these differences are due only to the way a telescope or any other viewing device forms the image.  It is well known that a refractor telescope with the eyepiece pointing along the length of the telescope shows an image that is upside down, while a pair of binoculars shows it correctly because it would be useless otherwise.  The problem is further compounded in another way.  If the image is seen through an eyepiece fitted into a mirror diagonal attached perpendicular to the telescope tube, even the orientation of the image changes as the diagonal holder is rotated about the telescope axis (a classic example being the orientation of Saturn and its ring system).  This is often necessary for viewing comfort. It would be a major irritant for terrestrial viewing, but perfectly acceptable for astronomical viewing where concepts like ‘up’, ‘down’, ‘right’ and ‘left’ are mostly irrelevant.  For an excellent write-up on the nuances of image orientation through common telescopes, please see:

Readers may have noticed that star charts show the East and West directions reversed as compared to geographical maps.  This is a long standing convention in Astronomy, dictated by the fact that when we lie down on our backs to view the night sky (this is indeed the best way to do so!) with the head facing north, our right hand points westward and the left hand eastward.  The situation is the other way round when we look at any geographical map.  This difference in convention is one major reason for the confusion.
As stated earlier, a telescope or other imaging device generally produces a change in the orientation of the image apart also from a reversal of ‘up’ and ‘down’ directions.  This is indeed the main cause for the confusing paths and locations so prominently noticed in webcasts and telecasts by most people during the transit of Venus.  All camera shots in this article show the Sun exactly the way our eyes see it since this is exactly what we expect from a camera.  Venus is seen to traverse east to west along a path north of the ecliptic and roughly parallel to it, consistent with the Espenak/NASA graphics shown in my previous post (note that north is to our left in the pictures).  However, the three NASA pictures taken through telescopes tell a different story because of the change in orientation of the image captured through the telescopes.  By thoughtfully employing the same geometry in all three of its telescopes NASA avoided compounding the confusion.  The path of Venus in these three pictures is roughly from top to bottom, whereas they are very nearly the opposite in the photographs, or as Dr Narsimhan has put it, ‘vertically from below upwards’.

In the final analysis, what is very nearly the same for all observers on Earth are the points of ingress and egress, and the path between these points, irrespective of the orientation of the picture being viewed.

Transit technique and Exoplanets

As pointed out in my previous post, the transit of Venus was used to determine the Astronomical Unit, a measure of distances on the scale of the solar system.  With the tremendous advances achieved in recent decades in astronomical instrumentation, both ground based and space based, a wholly new dimension to precision measurements has opened up and this transit of Venus is being used to fine tune the techniques involved.  They are already being employed to detect extra solar planets using a super sensitive light detector that is an integral part of the Kepler spacecraft.  This detector measures the extremely small variations in the intensities of light received from stars when a suspected planet makes a transit across the star just like the transit of Venus across the Sun.  Several hundred such exoplanets have already been found employing the transit technique.


As a rehearsal to observing the transit through a telescope equipped with a solar filter, I had looked for the sunspots which had suddenly spurted out in profusion just 3-4 days before the event.  What I saw was one of the most bewildering sights I had ever seen.  The field of view was sprayed with not just dark spots, large and small, but also large cobweb like dark grey patches which stole the show.  Then I suddenly realized that while most of the spots were indeed an integral part of the solar surface, the patches were produced by junk material that had collected inside my eye when I had suffered what is known as a posterior vitreous detachment some time ago.  My eye specialist had told me that this was only a ‘minor irritant’, something that I could afford to live with, considering how lucky I was to have escaped from any damage to my retina.  Considering how bad my vision is with my only ‘good’ eye, I am seriously reviewing my plan of visiting northeastern Australia to observe the total solar eclipse due on 13 November this year.  If I decide to stay put with my plan, it will be more because of the attraction of the Great Barrier Reef off the northeastern coast of Australia than the total solar eclipse for which the expected observing conditions are far from ideal anyway.

1 comment:

Unknown said...

Thanx to your earlier post I could see the transit of Venus very well from here. I have taken a couple of pictures as visible with the naked eye and posted the same on FB. We then got our fellow teachers and students to see the last part of the transit using a solar filter glasses which were thankfully provided by the University of Bahrain.
K Sudhir ( 1985 MScEd batch)
Sr PGT - Physics
The Indian School, Bahrain