White paint of radio telescopes

[mishima]

I was wondering what kind of paint is used for radio telescopes, generally.

In the case of the Green Bank Telescope, the idea is to get white at visible wavelengths, black at mid-infrared, and transparent at radio wavelengths. Titanium dioxide based paint was one substance cited on the internet. Is this universally true of all dish style radio telescopes?

 

[Simon Bridge]

Telescopes are painted to protect them from the elements.
You want the reflector to preferentially reflect the wavelengths that you want to look at and your surface coat may be chosen to help with that, you certainly don't want it to hinder it... so the telescope can still function as, you know, a telescope. Not sure why Green Bank wants to absorb IR though... maybe the dish works better when it's warm?

There is no set material for this - the materials used will vary with location and budget.

 

[mfb]

Not sure why Green Bank wants to absorb IR though... maybe the dish works better when it's warm?

IR absorption (and therefore emission) in the range of thermal wavelengths will keep the material cooler, in particular when the sun shines.

 

[SteamKing]

White paint also helps you see the damn things.

 

[Simon Bridge]

Oh right - like why desert nomads wear black.
@Steamking: tripping over radiotelescopes can be a problem?

 

[SteamKing]

It is if you fly into one.

 

[Simon Bridge]

Superman prefers that the high ones are florescent orange so they stand out against the snow... don't mind me: it's xmas here and I'm waiting for the turkey.

 

[mfb]

Oh right - like why desert nomads wear black.

Is that irony? White/black clothes are a difference in the visible spectrum - where a low absorption is useful. In sunshine, most objects absorb some part of the visible spectrum, and re-emit this energy as infrared. To stay cool, you want a low absorption of visible light and a strong emission of infrared. You cannot go below the temperature of the environment, but that is way better than black material in sunlight.

 

[Simon Bridge]

For body cooling in warm climates you want to favor convection since heat loss is mostly through sweating. Hence light loose clothing that you can wrap tight at night. I was just recognizing a connection - of course black to IR is cooler though naively one may suspect otherwise.