India’s largest liquid mirror telescope operates

The observatory at the top of Mount Devasthal houses the world’s largest liquid mirror telescope. It is made of mercury of a parabolic shape.

Telescope with a liquid metal mirror. Source:

How to create a telescope with a liquid mirror

Last year, the world’s largest liquid mirror telescope, the International Liquid Mirror Telescope (ILMT), was launched at the Indian Observatory on Mount Devastal. It is located at an altitude of 2500 m and is directed vertically upwards, so it cannot turn.

The main mirror of the telescope is a bowl with a diameter of 4 m with liquid metal. Mercury is used as the last one. The bowl rotates around its axis in 8 seconds with the help of motors. This creates centrifugal forces in the mercury inside, which give it a parabolic shape, so that light is refracted in the right way.

In order for the friction forces not to interfere, powerful pumps drive air under the mercury layer, creating a 10 mm thick layer between it and the surface of the bowl. Another pump creates a gas flow that prevents liquid metal from spilling out of the bowl.

The light after refraction hits the lens, it finally gathers it together and focuses on the photosensitive matrix, from which the reading takes place. Further, the data is processed by the Indian state Institute ARIES, which manages the entire observatory.

What are mercury telescopes for?

ILMT is not the first telescope with a liquid mirror. A similar instrument was the Large Zenith Telescope (LZT) near Vancouver. It is believed that the use of such a technical solution is cheaper than the manufacture of traditional mirrors. The last ones need to be very heavy to prevent deformation.

The new telescope will be used to observe short-term phenomena, such as variable stars and flashes of different nature. Its design is ideal for determining the details of their structure.

According to

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