The Extremely Large Telescope (ELT) will be the world's largest optical telescope. The telescope is being built by the European Southern Observatory (ESO). The ESO is made up of 16 countries which includes the UK and Ireland. The ELT is due to be complete at the end of 2027. 

The Subaru telescope is on Mauna Kea in Hawaii. It is run by the National Astronomical Observatory of Japan (NAOJ). From 1999 until 2005, it had the largest primary mirror in the world. Even today, its 8.2-metre main mirror is still one of the largest in the world.

The MMT is a telescope in Arizona, USA. It is run by the SAO and the University of Arizona. The area offers some of the best conditions for astronomy in the USA. This is because it is high above sea level, there is not much light pollution, and the skies are usually clear.