A Meridian Circle isn't your average backyard telescope. This precision instrument has been helping astronomers draw lines in the sky since the 18th century. It operates on a simple yet ingenious principle: measuring the exact moment a star crosses the local meridian line in the sky. And it was all made possible by Ole Christensen Rømer.

This Danish astronomer realised that a single instrument covering the full meridian would have a significant advantage, because stars could be observed to the north below the pole and the same stars again twelve hours later above the pole. In 1704, he finally managed to build a small observatory where he installed a meridian circle complete with a telescope, a divided circle, circle reading microscopes, and also meridian marks for adjusting the instrument.