What if the human eye isn't good enough?

Credit: ESO

The development of photography created a revolution in astronomy. But over the past decades electronic detectors have taken over. They ensure almost no single photon gets lost.

Big eye: With 256 million pixels, the 32-CCD OmegaCAM of ESO’s VLT Survey Telescope is one of the largest astronomical cameras in the world.
Credit: ESO/INAF-VST/OmegaCAM/O. Iwert
Cosmic surveyor: Thanks to OmegaCAM, the 2.6-metre VLT Survey Telescope at Cerro Paranal in Chile combines great sensitivity with a large field of view.
Credit: ESO
Raw beauty: This unprocessed image of the Helix Nebula, obtained with the Wide Field Imager at La Silla, still shows gaps between the camera’s 8 CCDs. The processed image can be found in section 4.
Credit: ESO

For some three centuries after the invention of the telescope, all observations were done by eye and recorded in notebooks. From the end of the 19th century, photography became a powerful new tool for astronomers: photographic plates could collect light over a long exposure time and reveal much fainter objects. Moreover, photography was much more objective. With the advent of charge-coupled devices (CCDs – the same detectors used in everyday digital cameras), astronomical detection techniques became more powerful than ever: CCDs are much more sensitive than the human eye.

Venetian glass
Venetian glass: The Doge of Venice peers through Galileo Galilei’s telescope. Until the early 20th century, visual observing was common practice.
Credit: Giuseppe Bertini

How well can you hear and see? A sensitive microphone can pick up sounds your ears can’t hear. In the same way, electronic detectors are much better at catching light than your own eyes.