Clear nights are precious, so what self-respecting skywatcher would waste one chasing clouds? Unless they’re noctilucent clouds, that is. These electric blue billows at the boundary between Earth and space incite the imagination and inspire us to keep watch at dusk for their arrival.
Noctilucent night-shining clouds return every summer between about 45° and 60° latitude, from May through August in the Northern Hemisphere or November through February in the Southern Hemisphere. Infrequent appearances and a habit for hugging the horizon make spotting them a quest akin to finding the Holy Grail…
read more Summer Quest for Noctilucent Clouds | Sky & Telescope.
