All about ILMT, Asia’s largest 4-meter telescope inaugurated in Uttarakhand

ILMT is the first liquid mirror telescope designed exclusively for astronomical observations located in Uttarakhand at an elevation of 2450 metres.

New Delhi,UPDATED: Mar 21, 2023 18:25 IST


Top view of the ILMT located at the Devasthal Observatory of ARIES showing the liquid mercury mirror covered by a thin mylar film. (Photo: ARIES)

By India Today Science Desk: Asia’s largest 4-meter International Liquid Mirror Telescope was launched in Devasthal in Uttarakhand on Tuesday. The observatory will explore the deep celestial sky, classifying objects from asteroids to supernovae, and space debris.

The telescope was inaugurated by Science & Technology minister Dr. Jitendra Singh, who said that the inauguration of the observatory places India at a different and much higher level of ability to study the mysteries of the skies and astronomy and to share the same with the rest of the world.


The International Liquid Mirror Telescope has a 4-meter-diameter rotating mirror made up of a thin layer of liquid mercury to collect and focus light. The metal mercury is in liquid form at room temperature, which is highly reflective and designed to survey the strip of the sky passing overhead each night.

A colour composite photograph of a small portion of the sky observed with the ILMT through the g, r and i Sloan filters. NGC 4274 Galaxy can be seen in the top right corner. (Photo: ARIES)

The telescope has three components: A ​bowl ​containing ​a ​reflecting ​liquid ​mercury metal, an ​air ​bearing (or motor) ​on which ​the ​liquid mirror ​sits, and a ​drive ​system. The mercury is protected from the wind by a scientific grade thin transparent film of mylar. The reflected light passes through a sophisticated multi-lens optical corrector that produces sharp images over a wide field of view and a 4k ⨯ 4k CCD camera, located above the mirror at the focus, records 22 arcminute wide strips of the sky.

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ILMT is the first liquid mirror telescope designed exclusively for astronomical observations and is the first optical survey telescope in India. The Devasthal observatory is equipped with the largest aperture telescope available in India that will use Big Data and Artificial Intelligence/Machine Learning (AI/ML) algorithms to classify objects in the sky.

The telescope 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. The data gathered by the telescope will be analyzed quickly using AI and machine learning to catalog the objects in the sky, including variable and transient stellar sources.

“The 3.6-meter DOT, with the availability of sophisticated back-end instruments, will allow rapid follow-up observations of the newly-detected transient sources with the adjacent ILMT. The data collected from the ILMT, over an operational time of 5 years, will be ideally suited to perform a deep photometric and astrometric variability survey,” the minister said.

Maintained by the Aryabhata Research Institute of Observational Sciences (ARIES), the telescope observed first light in May last year. It is a result of a collaboration between multiple international universities and scientific institutions.

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