A radio telescope

Secondary focus of RT4

Wheels at the base of the RT4 radio telescopeA few days ago, when I mentioned my trip to the Torun RT4 radio telescope in Poland, I promised some pictures of the dish. I've now got around to uploading some images so here is a mini tour of the telescope I visited.

Radio telescopes tend to have alt/az mounts, rather than Equatorial, as this is easier to engineer for large structures. So they rotate around horizontally (azimuth) and up-down (elevation or altitude). The azimuthal rotation is usually done with wheels on a railway track. The image to the right shows one of the sets of wheels at the base of the RT4. There are four sets of wheels on the outer track and some more on another track in the middle.

Climbing over the railway track, you can then ascend a metal staircase to reach the focus cabin underneath the dish surface. Climbing up some ladders you reach the top of the focus cabin and the place where all the radio receivers sit; the focus of the secondary mirror. You can then open a submarine-like hatch and climb out onto the surface itself.

On a sunny day the primary mirror can be dazzling as it is painted white and therefore reflects a lot of light. The surface is made from about seven rings of metal panels which reflect radio waves up to the secondary mirror. This is held in place by support legs which are just like the ones on the James Clerk Maxwell Telescope. The secondary mirror (see picture above) then reflects the radio waves down to the receiver cabin, in the middle of the primary mirror, where they are detected allowing astronomy to be done day or night.

It really isn't that different from an optical Cassegrain telescope, although you can't walk around inside a Meade LX200!

Posted in astro blog by Stuart on Saturday 02nd Jul 2005 (02:36 UTC) | Permalink
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