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

  • 5
    $\begingroup$ It's a high-tech version of the weather rock $\endgroup$
    – Mark
    Jan 8 '17 at 20:36

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

  • 1
    $\begingroup$ But beware of early morning frost on the glass sphere, which may diffuse the focus so that early sunshine is not recorded. $\endgroup$ Jan 11 '17 at 9:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.