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Radio Telescope

Observatory technician Hugh Lang prepares for the arrival of the new dish by removing one of the old radio antennas

Observatory technician Hugh Lang prepares for the arrival of the new dish by removing an old radio antenna.

A 3-m radio telescope dish was purchased during the summer of 2002 with a 21-cm receiver system for observing atomic Hydrogen. With this telescope we can observe the Hydrogen that exists in the space between the stars known as the interstellar medium. It allows us to study the amount of Hydrogen and its velocity, permitting measurements to be made of the rotation of our Galaxy. In this way we can see the large-scale structure of the Galaxy.


Dish assembly begins. Students Richard Baker and Luke Woolfenden with lecturer Derek Ward-Thompson and the first quadrant.

Dish assembly begins. Students Richard Baker and Luke Woolfenden with lecturer Derek Ward-Thompson.

The telescope was purchased commercially from Cassicorp and is a standard parabolic reflector, with its receiver at the prime focus. It has a 21-cm receiver, which collects the signals and communicates with a computer in the control room on the floor below. We can also control the telescope from the floor below.

The telescope is used by undergraduate students of Cardiff University, as well as by members of the Cardiff Astronomical Society. It is also available for viewing by school parties and members of the public during University Open Days.


The back of the radio dish, including the drive mechanisms. One has had its cover removed.

The back of the radio dish, including the drive mechanisms. One has had its cover removed.

 

The telescope operates at a wavelength of 21 cm, which is a wavelength at which cool atomic Hydrogen radiates in space. Hydrogen is the most abundant atom in the Universe, so by tracing Hydrogen we are in effect tracing the total mass in interstellar space.

By observing how bright the radiation is in a given direction we can measure how much Hydrogen is present.

By tracing how the wavelength of the radiation varies we can measure the velocity of the Hydrogen, using the Doppler shift.

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