Monday, December 12, 2011

Total Lunar Eclipse of December 10 in Retrospect

Doubt and Anxiety

This is the promised sequel to my last blog post alerting the readers to the total lunar eclipse of 10 December this year, the last such event visible from India for quite some time. I had signed off with a note of uncertainty and concern about the weather outlook for the day in the Mysore-Bangalore region, with the prospect of overcast skies and even some rain. This was in spite of the fact that the wintry month of December is normally known to offer some of the finest conditions for night sky observations, with wonderfully clear skies.  My anxiety was strongly reinforced on the evening of the previous day which turned out to be a disaster in Mysore, with dense clouds blotting out the near full Moon most of the time. It was therefore not without considerable misgivings that my friends and I woke up the next morning, with cloudy periods alternating rather ominously with bouts of sunny weather. But the outlook improved distinctly as the day progressed.
Viewing Site

A small group of us, including Chiranjeevi and Mr Krishnamurthy, set up camp at a somewhat remote location, about 15 km west of Mysore city.  This was the same place they had used for viewing the June 15-16 total lunar eclipse that I had skipped in favor of the comfort of my home when the weather had threatened a washout of the event, but relented dramatically as the event arrived [see my earlier blog post titled "Total Lunar Eclipse in Retrospect (Jun 11)"].  Though not so dramatically, the weather that had threatened a washout yet again relented that evening too and it was absolutely clear skies most of time.  This was in sharp contrast to what our numerous friends reported live from Bangalore, a nearly total washout, particularly during the totality of the eclipse.  The 'weather gods' were on our side once again!

Our equipment included my Meade ETX127 Maksutov-Cassegrain catadioptric telescope with a Canon 350D DSRL camera, a Sigma DC 18-200 mm lens, my trusted light weight Lumix DMC-FZ35 camera with up to 72x zoom setting, two sturdy tripods and two pairs of binoculars.
Though there were no street lights nearby, the distant city lights to the east where much of the action was to take place were definitely not welcome that evening. It was apparently much better last time because the eclipse was seen in the southwest, with hardly any light pollution from that direction.

The Event

Soon after sunset, we saw as expected a giant sized faint yellowish full Moon rising north of the eastern horizon and my Lumix camera captured its first of numerous pictures that day.  Here it is, bathed in lingering daylight against the backdrop of some rather ugly human imprint:

The characteristic color of the rising or setting Moon (or the Sun) is because of strong scattering of light through the dense atmosphere skirting the earth's surface, with the higher wavelength light in the red/yellow end of the visible spectrum getting scattered more towards the surface.  However, the inflated size of the object has no such physical reason, though most people think there is some physics behind the phenomenon.  It is in fact purely an optical illusion since the same object will appear in 'normal' size after it has risen well above the horizon.

Just five minutes later the Moon had risen higher up and brightened up sufficiently for me to capture the following view, appearing to be suspended in mid air, still looking pretty big.  It didn't show any visible indication that it was already passing through the penumbral phase of the eclipse. It was only seven minutes away from entering the umbral shadow of the earth.

The partial (umbral) phase of the eclipse began around 6:15 PM as predicted.  In contrast to the vastly more complex weather phenomena, the predictability of astronomical events of any kind is amazingly accurate, thanks almost entirely to Newton and his laws of motion and gravitation. How edifying that we were experiencing both of these, concurrently and cooperatively!

The following mosaic of pictures presents the sequence of events over the next three hours, captured after the onset of the partial phase, till close to its end after passage through totality, at convenient though irregular intervals. All these pictures were taken at 18x zoom with the aperture set at maximum (f/4.4) and focal length 86.4 mm.  The shutter speed varied from 0.1 sec to 1.2 sec, all at a sensitivity of 400 ISO.

The first two pictures show the halo around the Moon caused by some thin hazy clouds in the region that lingered for about half an hour. Remnants of this can still be seen in the third picture taken at 6:50 PM.  Thereafter, the sky was wonderfully clear everywhere and we made the best of this opportunity by combining our eclipse observations with some keen stargazing for which the winter night sky is particularly exciting.
As could be expected, the umbral shadow on the Moon was seen to advance from northwest to southeast as the partial eclipse progressed. The picture taken at 7:33 PM was just before the onset of totality, with a sliver of the sunlit lunar face still visible in the southwest.  When the next picture at 7:45 PM was taken, the eclipse was well into totality, but the southwestern edge still appears to be somewhat bright, certainly brighter than the rest of the lunar surface. This is due to the fact that during totality, the lunar surface was located well inside the southern half of the earth's shadow and hence received more scattered light than the rest of the surface (see the NASA/Espenak figure presented in my last blog post). This sliver shifted towards the southeastern edge (from the 'four o'clock position to the eight o'clock position' as Mr Krishnamurthy described at that time) as the total phase progressed. This is apparent from the picture taken at 8:18 PM when it was still inside totality which incidentally ended around 8:27 PM.  The three pictures from 8:40 PM onwards show the symmetrical reversal of the partial phase after the end of totality.

During totality, the reddish face of the fully eclipsed Moon appeared to be somewhat brighter than expected considering that the scattering effects of the earth's atmosphere in winter should be less than at other times.  On the Danjon scale of lunar eclipse brightness, my estimate was that it corresponded to somewhere between L=2 and L=3.  However, as most eclipse watchers are aware, predicting this in advance is nearly as difficult as predicting the weather to which it is related in some ways.

I also took a number of pictures at the full zoom level of 72x in my Lumix camera.  Here is a picture taken towards the end of totality at around 8:12 PM.  The asymmetric illumination of the surface, with a pronounced brightness at the southern edge (right) as pointed out and explained earlier, is more clearly noticeable here.

My telescope could not be used adequately for photography, particularly for want of an electrical outlet to keep the drive running.  It occurred too late to me that we should have carried a portable battery. However, it came in very handy for visual observations of the various phases of the eclipse and other celestial objects.  The telescopic view of the lunar disk during totality was breathtaking, with the whole of it just filling the field of view through a low power eyepiece.

The Sidelights

Eclipses often present opportunities for some nature photography.  I took the following picture sometime after the onset of the partial phase.  The exposure time was 30 seconds at f/4 (18 mm focal length, ISO 100). It captures the city lights against the backdrop of a picturesque tree in the right foreground.  The first magnitude star Aldebaran in the constellation Taurus can be seen near the Moon.  A number of fainter stars are also seen despite the rather conspicuous haze enveloping the Moon.

[This and the rest of the pictures in this post are in high resolution and can be blown up to their full size by clicking on a picture and opening it in a separate window

On my suggestion, Chiranjeevi went close to the tree seen in the above picture and shot the following two pictures, both highlighting the tree as much as the Moon and the sky. 

The first one is a particularly beautiful picture capturing part of the tree with its branches and, in a sense, eclipsing the eclipsed Moon itself.  The brightness of the tree itself is due to headlights from a vehicle passing by on the road next to it. Taken around 8 PM, it also shows the rising Orion constellation and the rich star field nearby.  What a wonderful amalgamation of Nature at the celestial and terrestrial levels! The picture parameters were the same as for my own previous picture, though the Canon DSLR camera had been used and the sensitivity set at ISO 400. The second, taken half an hour earlier, had similar settings, but with a higher focal length of 63 mm and shows a much larger image of the Moon.

Chiranjeevi also took the following rather overexposed picture at 8:35 PM showing the totally eclipsed Moon much brighter than it actually was, and in the process capturing a large number of stars and their constellations, particularly Orion and Taurus.  The brightness in the lower part of the picture is contributed by city lights. The exposure was for 30 seconds at f/4 (focal length 18 mm at ISO 400) on the Canon DSLR.

Closing Shop

We took our last pictures around 9.30 PM and started dismantling our equipment without waiting for the Moon to regain its full glory.  Before this, the following picture of our small group was taken with a self-timer.  Chiranjeevi is at extreme right and Krishnamurthy is to my right.

We had spent nearly four hours in the field with no amenities of any kind nearby, but with a richly rewarding experience we could all take home for the day and beyond.  We felt particularly grateful to nature for providing such an opportunity, something that had been denied to scores of our friends in Bangalore and thousands of other enthusiasts in that megapolis.


Back home around 11 PM, I just chanced to tune into a Kannada TV channel and paused to watch it since it was devoted to the day's news. It came as no surprise that most of the eclipse related news was dominated by the kind of rituals performed in the day to ward off the evil effects of the eclipse, mostly in temples thronged by huge crowds of people.  There was hardly any coverage or news of the event itself.  As usual, Nature's magnificent performance that night meant nothing to most people, including the vast majority of students, teachers and other intellectuals.

1 comment:

A V G Rao said...

Interesting narration & excellent photos