A Step Closer to the Mystery of the Universe
Modern telescopes differ widely in design depending on what they are to be used for. “ZERODUR®” is very frequently used as the material for mirror blanks.
Whereas telescopes at one time were pure observation instruments, through which astronomers used to view the night sky for hours on end, nowadays they are serving increasingly as measuring instruments. Instead of the human eye, CCD chips (Charge-Coupled Device, a semiconductor material component for processing electrical and optical signals) are used as receivers and data collected is stored and processed in computers. Modern astronomy is also no longer restricted to visible light. The entire bandwidth of electromagnetic radiation in the universe can be investigated with different types of telescopes.
Modern telescopes differ widely in design depending on what they are to be used for. “ZERODUR®” is very frequently used as the material for mirror blanks.
Whereas telescopes at one time were pure observation instruments, through which astronomers used to view the night sky for hours on end, nowadays they are serving increasingly as measuring instruments. Instead of the human eye, CCD chips (Charge-Coupled Device, a semiconductor material component for processing electrical and optical signals) are used as receivers and data collected is stored and processed in computers. Modern astronomy is also no longer restricted to visible light. The entire bandwidth of electromagnetic radiation in the universe can be investigated with different types of telescopes.

VLT
![]() The fourth 8.2 meter telescope mirror receiving its fine polishing treatment at the French company REOSC. | ![]() The VLT is located on the 2660 meter high Cerro Paranal in the Atacama Desert in Chile. |

GTC

With a diameter of 10.4 meters and a maximum size of 11.3 meters the GTC is one of the world’s largest telescopes. The primary mirror is composed of 36 “ZERODUR®” glass ceramic hexagons.

Chandra

The Chandra observatory circles the Earth in an elliptical orbit at a distance between 10,000 and 140,000 kilometers and is thus well away from radiation belts that could interfere with its operations.
When X-rays strike matter head on, they penetrate deep inside or even pass right through it. For that reason, special cylindrical “ZERODUR®” mirrors were developed for Chandra which are arranged so that the X-rays are reflected at a grazing incidence and are then reflected onto the detectors.

SOFIA
![]() SOFIA airborne telescope: the optical instrument is installed in the Boeing 747’s fuselage. | ![]() A honeycomb structure has been milled out of the reverse side of the “ZERODUR®” mirror blank, reducing its weight from four tonnes to 850 kilograms. |