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North-West University Radio Astronomy Practical 2004/03/16

Six Physics Honours students from the North-West University Potchefstroom campus under the tutelage of Prof. Johan van der Walt carried out their Radio Astronomy Practical at HartRAO from 2004 March 16 - 19. HartRAO astronomers Mike Gaylard and Sarah Buchner kept the students busy during their stay.

The practical started by using a satellite dish to measure the brightness temperature of the Sun, and then to deduce its physical temperature at 12 GHz. This was followed by an investigation into the radio emission from pulsars, and a measurement of the dispersion measure towards a pulsar. Thursday started with a trip up the telescope to get a first hand look at their research instrument. The images below capture some moments on the telescope.

group on telescope
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Made it up the ladders! The group celebrate their arrival in the main surface of the 26-m telescope.

18cm feed
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The microwave feed horn for the 18cm receiver is too large to fit in the Cassegrain cone. Here it is pictured after inspection by the students.

down the ladder
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For some the trip down again is a little scary... its a long way down.

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A celebratory photo at the foot of the ladder - the whole group made it up and down in one piece.

The rest of thursday was spent predicting what planets we should be able to observe with the telescope in the various receeiver bands, then setting up observations of those likely to be detectable.

On friday the student got to grips with radio spectroscopy. First a quick refresher was held on optical spectroscopy. The students are seen in action below.

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What is the spectrum of light from an incandescent lamp? The students' predictions did not all match what they then saw... Different types of light sources produced some unexpected results.

The students then switched to radio spectroscopy and observed a hydrogen recombination line at 6cm wavelength from an ionized hydrogen region. Combining the result with the continuum emission intensity enabled them to derive the electron temperature of the HII region. The excess width of the emission line over the expected thermal width led to an investigation of the turbulence in the emitting region, and the factors that control the bulk motions of the gas.