The larger a telescope's primary mirror, the greater its light-grasping capacity. The diameter of the GTC’s mirror will be 0.4 m greater than that of any telescope previously built. However, this is not the most striking feature of the Gran Telescopio CANARIAS.
What makes it important is the collection of unique features that together will put the GTC in a leading position from the moment it enters service. Working together, all of these different parts will ensure that the optical system benefits from the best conditions for observation.
Another important property of the GTC is its ‘angular resolution’, the sharpness or image quality in simple language.
Every part of the telescope is at the service of the optics: the mechanics, the enclosure and dome, the electronics and control systems... all exist to ensure that the image is perfect and stays perfect while the telescope is observing. Unlike telescopes of just 20 years ago, modern telescopes use active optics, an optical system that is self-monitoring and makes corrections when they are needed.
There is more. Image quality is affected by changes in the atmosphere while the telescope is observing. However, the world’s most important research centres are working hard to develop what is called ‘adaptive optics’. As the name suggests this involves using systems that bend the mirrors to compensate for small amounts of turbulence - which affect the light’s trajectory - as they occur.