Night-time seeing and atmospheric behaviour in the Canary Islands Observatories

The Canarian Observatories have become two of the most studies ones and are a privilleged place for astronomical observations. Since the sixties when, for the first time, Prof. Sanchez installed equipments to test the atmosphere at Observatorio del Teide (O.T., Tenerife), the campaigns carried out not only at Izana but also at Roque de los Muchachos Observatory (O.R.M., La Palma), have been numerous.