A Polish dish


IMAGE: The Torun RT4 radio telescope
The Universe can be observed throughout most of the electromagnetic spectrum. The atmosphere, luckily for life on Earth, blocks most of the EM spectrum only allowing us a few small windows to see through. Most people are familiar with one of these windows - the optical window - as that is how you see stars when you go outside at night. Optical telescopes (and your eyes of course) look at colours with wavelengths that are less than a millionth of a metre long. One of the other atmospheric windows exists in the radio part of the spectrum; where the lengths of the waves range from millimetres to around 10 metres. You could almost imagine measuring them with a ruler. This part of the spectrum also gets used for radio broadcasts, WIFI connections and mobile phones. One of the advantages of radio astronomy is that you can observe during the day and even through clouds. A good thing if you live where I do.

Radio astronomers use large antenna - affectionately known by some as 'bits of bent metal' - to collect the radio waves to a focus in the same way as optical astronomers do with lenses or mirrors. If you have a telescope you will know that the bigger the diameter of your light (or radio) bucket, the better your images both in quality and resolution. In this case size really does matter. A medium-sized radio telescope is about 30m (100ft) in diameter but big ones, such as the Lovell or Robert C. Byrd telescopes, tend to be three times bigger than that.

I'm currently at the Torun Centre for Astronomy in Poland where they have a 32-metre Cassegrain radio telescope which observes the sky at wavelengths from about 21cm down to 1cm (1.4 to 30 GHz). It is a nice dish that has improved quite a lot in the past couple of years as they have made the dish surface more accurate. It should improve even more in the next couple of years as it carrys out surveys of things in the radio sky.

I went up into the dish yesterday so I will post some pictures later. It is always a great experience to go up a radio telescope, especially on a nice sunny day, as the white surface looks really stunning against a blue sky. In fact, I could have done with some sunglasses as it was like being on top of a snow covered mountain. The picture shows the dish pointing upwards (it wasn't being used) with the secondary reflecting mirror sticking out at the top.

Posted in astro blog by Stuart on Wednesday 29th Jun 2005 (14:28 UTC) | Permalink
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