Tag Archives: reflector

I Can Hear You Coming

CRW_0313.jpgIn the days before radar, there were other techniques that were used for trying to detect inbound enemy aircraft.  One of them was the use of sound.  Dotted along the southeast coast of the U.K. are a number of locations with devices for focusing sound.  One of them is located in the hills above Hythe.  This is one of the simpler forms that were used.  Despite the age, the contract structure is still in good shape.  With the introduction of radar, these sites were redundant but they do provide an insight into the trying of any idea to gain an advantage in another era.

Shane 3m Reflector

AU0E3325.jpgIf you know your optical telescopes, you know there are two main types – refractors and reflectors. Refractors use lenses to magnify the image and reflectors use mirrors. Reflectors can be much larger and gather more light so took over from the traditional telescopes. At the Lick Observatory, they have the Shane 3m Reflector. (For those who can’t use sensible units, 3 metres is 10 feet.) the building that houses the telescope has a visitors gallery. You aren’t in the room with the telescope but you can see into the space that houses it.

AU0E3337.jpgThere are a number of display screens showing how it works and how it was constructed. The clever stuff is out of sight and the main structure is all about holding the mirrors in the right place and reorienting them when required to track a subject. The structures are some substantial bits of steel and getting them up the mountain was no small feat. Nothing was in use while we were there (during the day!) so you had to imagine this large structure being moved around to track the next celestial body. Given that the building has to be at ambient temperature to avoid any heat distortion when I use, I think I was quite glad it wasn’t working since it was a cold and snowy day up on the mountain.