International Liquid Mirror Telescope at Devasthal

Context: Asia’s largest 4-metre International Liquid Mirror Telescope was inaugurated at Devasthal observatory in Uttarakhand. 

About the Telescope:

  • ILMT employs a 4-metre-diameter rotating mirror made up of a thin layer of liquid mercury, to collect and focus light.
    • Mercury has strong reflective power and stays in a liquid form at room temperature. Also, it is much cheaper than glass mirrors.
  • It is the first liquid mirror telescope designed exclusively for astronomical observations, the largest aperture telescope available in India and also the first optical survey telescope in the country. 
  • It is located at an altitude of 2450 metres at the Devasthal Observatory campus of Aryabhatta Research Institute of Observational Sciences (ARIES).


  • There are primarily three ​components in a liquid mirror telescope: 
  1. A ​bowl ​containing ​a ​reflecting ​liquid ​metal ​(essentially ​mercury)
  2. An ​air ​bearing (or motor) ​on which ​the ​liquid mirror ​sits
  3. drive ​system
  • Liquid mirror telescopes take advantage of the fact that the surface of a rotating liquid naturally takes on a parabolic shape (under the influence of gravity and centrifugal force), which is ideal for focusing light.
  • The reflected light passes through a sophisticated multi-lens optical corrector that produces sharp images over a wide field of view. 
I read somewhere that mercury is being used to make liquid-mirror  telescopes. What are the advantages of collecting light this way? |


  • ILMT is designed to survey the strip of the sky passing overhead each night, allowing it to detect transient or variable celestial objects such as supernovae, gravitational lenses, space debris, and asteroids.
  • While scanning the strip of the sky every night, the telescope will generate nearly 10-15 Gigabytes of data. This ILMT-generated data will permit the application of Big Data and Artificial Intelligence/Machine Learning (AI/ML) algorithms that will be implemented for classifying the objects observed with the ILMT. 
  • It enhances India’s capabilities to explore the mysteries of the deep celestial sky and astronomy. The data collected over an operational time of 5 years, will be ideally suited to perform a deep photometric and astrometric variability survey.

Prelims Practise Question:

Q. Consider the following statements:

1. Liquid mirror telescope uses a thin layer of Mercury to form a parabolic reflecting surface.

2. The first optical survey telescope in India has been inaugurated in Hanle observatory Ladakh.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2

Answer: (a)

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