Telescopes from the Ground Up

The dish network

The VLA is an interferometer made up of 27 radio telescopes arranged in the shape of a Y. Each dish is 82 feet (25 meters) across and weighs 230 tons. The spacing between the dishes can be changed to allow different types of observations to take place.

The farther apart the dishes are, the better the telescope’s resolution, or ability to distinguish between two close objects. When the dishes are closer together, the resolution is less, but the telescope can get more information about characteristics such as the object’s brightness and temperature.

No matter how astronomers arrange the dishes, the light-gathering power of the telescope always remains the same. This is because the total area of the dishes is always the same no matter what position they occupy. The VLA has the same light-gathering area as a dish the size of two and a half football fields.

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Radio Telescopes