Thanks a lot!
While working at Mt. Wilson Observatory, I would encounter these vast marine layers. When we incurred one that was 4000 ft. thick, it would be black as pitch on the mountain at night. Occurring in June, most reliably, these marine layers enabled galactic photography to practiced at a high quality level from the Newtonian focus of the 100" Hooker telescope. Even today this level of observation is obtainable. When these marine inversion layers occur, the air mass flowing across the mountain is very smooth. The "seeing" at Mt. Wilson is still some of the finest in the world.