Thursday, November 25, 2010

False Dawn

Many have been fooled into thinking that it marks the start of morning twilight. Indeed the Persian astronomer Omar Khayyam referred to this ghostly glow as the "false dawn" in his poem, The Rubaiyat.

When false dawn streaks the east with cold, gray line,

Pour in your cups the pure blood of the vine;

The truth, they say, tastes bitter in the mouth,

This is a token that the “Truth” is wine.

Unlike the stars of the Milky Way, which stretch away from Earth for light-years, the source of false dawn lies between the inner planets of our Solar System. Billions of dust grains orbit the sun in a flattened disk spread out along the ecliptic. Many of these particles were ejected by comets. The dust reflects and scatters sunlight creating a visible triangular glow above the horizon.

It can be seen for up to an hour before true dawn begins to break. Unlike true dawn, though, there’s no rosy colour to the false dawn. The reddish skies at dawn and dusk are caused by Earth’s atmosphere, false dawn originates far outside our atmosphere. You are looking edgewise view into our own solar system.

The sub zero cold, early hours would bring this humongous Zodiacal Light right on schedule each night at Indian Astronomical Observatory, Hanle, Ladakh brighter than the Milky Way and rising to great heights. It was a sight to fix your gaze upon, one could never get used to it.

Hope this image conveys just a little of how I felt the 6 nights I was at that
wondrous place on top of the world.

Ajay Talwar
November 26th, 2010

Thursday, November 18, 2010

Kemble's Cascade

The constellation of Camelopardalis, no not a camel, but a Giraffe, is a northerly one surrounded by Cassiopeia, Perseus, Auriga, Lynx, Ursa Major, Draco & Ursa Minor. Milky Way wanders into the territorial area of the Camelopardalis towards the side touching Cassiopeia & Perseus. Camelopardalis contains a colourful asterism called Kemble's Cascade containing more than 20 stars, spanning more than 2½° in the shape of a cascade. The cascade contains colourful 8th mag stars leading to open cluster NGC1502.

Kemble's Cascade can be seen easily in binoculars. Start from Algol, proceed to Mirfak, the brightest star of Perseus and continue the same distance to locate Kemble's Cascade. Another way to locate it is using Cassiopeia. Start from Caph, head towards Segin and follow the same distance and direction to Kamble's Cascade. Caph and Segin are the two end stars of the W of Cassiopeia.

I shot this asterism through a 200mm lens from IAO, Hanle, Ladakh. Hope you like the photograph.

Wednesday, June 2, 2010

DOT, and my visit to that dot on the map

DOT – Devsthal Optical Telescope

Kathgodam, Bhimtal, Khutani, Padampuri, Dhari, Dhanachuli Bend, Jhirapani, Devsthal. No internet mapping sites makes or measures the route for you. The pine filled road is not even visible in Google Earth. The route to Devsthal is approximately 40 kms through the hills on a road with very few vehicles and not many tourists. In about one hour from Kathgodam, which is at a height of less than 500 metres, on to Devsthal, you climb to a height of 2424 metres. Dhanachuli bend is the last four road crossing you encounter on the route upwards where you have a few shops, tea stalls and restaurants. The last village that you encounter, Jhirapani, seems like an abandoned one. The road to the observatory campus leads from in-between two houses; you would certainly miss the turn unless you’ve been told. I just wonder when the transport carrying parts of the biggest telescope arrives here, how it will turn towards the last road. A sky blue coloured board proclaims the site to belong to ARIES and that entry is restricted.

The road leading inside the campus has been metalled recently and the 3 km drive inside is smooth. The campus is full of Pine, Oak, Cedar and other exotic trees, all tall, old and majestic, rising till great heights, on the hilly slopes. The campus is 3 kms long but has very little flat or clear area. The observatory would have to be built only in places where nature allows. Continuing on the observatory campus road, you see that some essential buildings like the store room, power distribution room, have already been completed and a guest house is under construction.

Halfway on the road, there exists a beautiful meadow. A vacant grassy plot surrounded on three sides by the natural sky scrapers, trees! I settled my 8” telescope at this beautiful spot for the Venus Occulatation the next day, right beside the ancient 22” telescope shed. A little distance away, is a prefabricated, and assembled two room guest house, complete with all facilities including an internet & UPS enabled windows desktop, wow, all within 50m of my observing site. Ideal is the correct word, and all thanks to the hospitality provided by ARIES to me. Thanks Prof. Ram Sagar and thanks Dr. Wahab Uddin.

It’s almost a secret new site. It’s almost like no one knows about it. I am sure that is about to change in a few months from now, but for now the meadow was beautifully welcoming for the three nights I spent at Devsthal. Soon enough the meadow will be the busy place to store the arrival of all the parts of the 3.6 metre telescope, the largest in Asia. The large, thin mirror telescope will be setup at the end of the 3 km road on the peak. The telescope will be on a modern Alt-Azimuth mounting and a new style dome, a la observatory at Girawali, as opposed to a classical dome with a vertical window. The natural prevailing winds from the north west would be effectively used to cool down the telescope temperatures before it is time to open the observatory in the evenings. The actual telescope would also be at a good height from the ground level, on the peak. One, because the trees would not have to felled and second, the height of telescope would eliminate the local thermal effects of the grounds surrounding the observatory, both of the reasons more important than the other! The telescope is scheduled for installation completion at the end of year 2012.

Closer in time though, is another telescope, a 1.3 metre telescope, which should be ready by the beginning of the next year. I went and saw the enclosure, unconventional for such a large telescope, is a roll off roof, completely baring the telescope to the weather outside, which would make it perform better. The 1.3 metre telescope would be installed on an equatorial fork mount. At the time I was at Devsthal, the news was received that the telescope had arrived at Delhi and customs inspection was being carried out.

And little in the future, as Prof. Ram Sagar told me, Devsthal will have a 4 metre Liquid Mirror Telescope installed. As the telescope will be fixed, it will only be able to ‘Look Up’, at a narrow band of the sky, and will not be able to track any sky objects. The only small amount of tracking that would be possible, when the object would fall within the field of view of the large CCD installed at its focus, as the object would traverse the CCD pixels, software would negate the moment.

As you can imagine I was excited being at such a beautiful astronomical spot with clear blue skies, and equally excited at the prospects of this site, DOT, to becoming a great centre of optical astronomy in India. A future that I can almost imagine effortlessly. Here is one photo that I shot here during my 3 night stay at the DOT, which almost describes the meadow where I was.

Will the meadow stay though?

Ajay Talwar