Noctiludent clouds are a clouds that are appr. 70-90 km high from the ground level in Mesosphere. Noctiludent cloud phenomena can be observed when the Sun is about 4 to 16 degrees below the horizon. Here in Finland noctiludent clouds are most common in July and in the beginning of August.
Below are some noctiludent cloud pictures taken by the Markku Nissinen in Varkaus region (mostly in Taurus Hill Observatory). More noctiludent cloud pictures can be found from our gallery.