Chasing a runaway Comet

Comets are a good omen. No, your astrologer would not agree, I know. But for astronomy buffs comets are always welcome visitors. They have a great attraction not easily paralleled by most other celestial objects. In fact, my own interest in astronomy owes a lot to the Halley's comet that did its last trip into the inner solar system in the mid 1980's.

Other comets like Hale Bopp, Hyakutake, Holmes and now Lulin have all left their mark in the skies, so to say. Contrary to common belief comets are not that rare. In fact, on any given night there are a handful of them around but most of them are only visible only through telescopes; quite a few of them will need a fairly big instrument to really see any details. Therefore, every time a bright comet visible to the naked eye comes around, it creates a lot of excitement.

Scientifically, comets are important since they are believed to carry with them the primordial matter not cooked by effects of solar radiation. Astronomers believe that studying comets can throw a lot of light on the conditions that existed in the early days of the solar system's formation.

A comet has broadly three parts: The nucleus which is the "dirty snow ball" and the only permanent part of the comet, the Coma and of course the tail. What makes comets so interesting to the general public is of course their tail and to a lesser extent the coma. The nucleus is just a few kilometers across - something like a small mountain on the Earth. This rocky, icy mountain contains plenty of dust too. And because they don’t reflect much light (measured by albedo, the reflectivity) they go unnoticed for most of their life time. But when a comet comes closer to the Sun, the ices melt/sublime and the gases thus produced bloat up in size and the comet's coma can grow into several thousand kilometers and the tail can grow into millions of kilometers. And that’s what gives the comets their typical structure and the size. After spending a few months in this glory they disappear from view only to return after a few years in most cases. Some of the comets may never be seen again.

The recent appearance of comet Lulin gave us yet another excuse to make a trip to our usual haunt near Mysore. We wanted to take some pictures of this "green" comet. Of course, we don't have the sophisticated drive and other equipment to take professional quality pictures but that does not deter us from trying to get what we can! The pictures of Holmes we had taken last year were still fresh in memory. That was absolutely breathtaking, with the coma appearing as big as the disk of the moon! And was that bright!

So we were off to Mysore; myself, Seema, Gaurav, Dilip and Akshay,. We started from my place around 6 pm and reached our destination 165 km away around 9.30 pm. After a short, ten minutes rest, we went out to see if the comet was visible. It was barely visible to the naked eye but easily seen in binoculars. Through my 5" the coma was quite bright and the tail was visible too.

And then were busy setting up our telescopes for photography. Dilip started off with the six inch telescope and the drive assembly (see here for a description on basic astrophotography and equipment that was used for these pictures) that he had recently got modified and I started setting up my Meade 5" scope.

As it happens so many times, especially after a long journey, fixing the stuff and getting a proper polar alignment took quite some time on the six inch. In the mean time I had started taking some pictures with my Meade, experimenting with polar alignment for the first time. The tube was precariously positioned and with camera hanging upside down and I had to get into some yogic postures to look through the eyepiece/view finder. The tracking was quite ok and I wanted to take multiple exposure and try to stack them to get some acceptable pictures. So most exposures were around two minutes. The images were quite sharp. In the meantime, Dilip was fighting with his setup to get things on track. In fact, by the time Dilip got a proper alignment and ready to shoot it was around 2 am. Time to retire for the day - or night - actually. But our day had just begun. And Dilip started taking pictures. He got a couple of good shots in the session and decided to close by 4 am. Off he went to take a nap and while going remarked that it was the first time in his life he had stayed on till 4 am during an observing session!

It was my turn to try and take some pictures now. Since everyone else had gone to sleep I was working alone in absolutely silence. The alignment was really good and there was no need for any dec correction. After taking a few exposures I decided to close my photo session at 5 am. There was a hint of twilight by now and I was quite tired with my back protesting and hands aching with tracking. It’s been a long night.

The next morning we got up around 8 am and after a good breakfast prepared by Seema downloaded the pictures. When running through the pictures we were surprised to see the amount of shift in the comet’s position. Though we knew that the comet was really running against the starry background, the shift in position seen within minutes was a revelation. The time difference between pictures was about 6-7 minutes and the shift was easily seen between pictures. We knew that it would make an interesting video clip. But we were too tired after a night’s work and did not think about going about it. The clip was ultimately done after returning to Bangalore.

Here are a couple of pictures of the Comet taken over the two weekends in Feb 09:

Here is a video clip made with eight different exposures over a period of 47 minutes and here is a video clip made with four different exposures over a period of 30 minutes.

We generally mix astrophotography with another of our interests – going after birds. But this time we were just too exhausted and stay put in the farm house. Dilip was leaving for a trek in the afternoon and after a leisurely lunch I decided to take a much needed nap. I would have probably slept for an hour when the phone rang. It was Dilip on the line. He had seen a group of bar headed geese in a lake on the way to Hunsur. He wanted to know whether I would be interested in a short drive to check out what I could get. Well, it was too tempting and I didn’t take long to decide that I was going. It was around 3 pm when Dilip called and after a quick shower I was ready to go around 4 pm.

There were about a hundred of these cute birds in the lake. And of course, the common coot, little grebe and other common water fowl were all there aplenty. But there was one which was looking somewhat different and not seen before. It was a cute little goose. Since I had not carried my bird watcher’s guide, could not recognize it immediately. After returning to Bangalore and a quick check showed that I had got the Cotton Pygmy Goose. A good catch! The picture below is of a juvenile Pygmy and the one next is of an adult bird.

On the way back I noticed a black shouldered kite on a tree perched at the very top and stopped to see if I could get a good shot. He was quite co-operative and did not get alerted. In a tree next to this one there were a noisy group of rosy starlings and got a couple of good pictures.

After the return to our base it was time to take out the telescopes and start with our star shooting all over again. Since Dilip was not around, I had the entire telescope time to myself. The comet was in the East now. Due to the limitation with our equipment, objects that are in the East are to be tracked by turning the knob with the left hand and that turned out to be quite a challenge. After struggling for an hour and getting a few reasonably bad (!) pictures I decided to stop trying and shifted to my Meade with 17-70 lens piggybacking on it. I managed a dozen or so reasonably good images by mounting it in equatorial configuration. It was now around 1.30 and I decided to take a short nap.

When I woke up at 3 am the comet had crossed the meridian and was comfortably located in the western sky. So I was at it again, alone under the skies in complete silence save for the occasional call of an owl and the thud from the falling coconuts. Thanks to the power cut it was pitch dark and there was no one disturb me either. Ideal conditions for some astrophotography!

After getting ten pictures of the comet I briefly turned to a couple of open clusters in Scorpio just for a change. But this was in the South-East and I had to become a leftie again. That was too much of hard work at 5 am and it was time to stop and return to the comfort of the bed. When I woke up for the second time that morning it was well past 8 am. It was a sound sleep after a long night under the skies. And time to start packing up.

We returned in the last week of Feb again to get some more shots of the comet. The temptation was too strong. By next week moon would be getting brighter and closer to the comet and the "star with hair" would be lost in the glare of the moon for at least ten days. And after that the comet would be in the evening sky, probably lost in the twilight and in any case getting fainter by the day. We did two nights of shooting again and it was time to say goodbye to Lulin.