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I found what looks like a "crystal ball" in a meteorological station in the Vlădeasa mountains (Romania). What is its purpose?

enter image description here

JeopardyTempest
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1 Answers1

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It's a Campbell-Stokes sunshine recorder, used to record the times at which the sun is shining. It acts as a lens, focusing the sunlight onto a piece of card. If the sun is shining, the focused beam will burn a hole through the card at that point.

Here's a closer view of a sunshine recorder in Wendelstein, Bavaria: Sunshine recorder Source: Wikimedia Commons

And here's a used recording card with holes burned through it: Recording card Source: Wikimedia Commons

Pont
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    But beware of early morning frost on the glass sphere, which may diffuse the focus so that early sunshine is not recorded. – Gordon Stanger Jan 11 '17 at 09:03