The Blue Period

I was at the Cradle of Aviation the other day for the training class for Project Astro. You already know that. Anyhow, when I left the building I looked up while walking under the entrance covering and stopped in my tracks. What grabbed me was the dramatic color difference between the warm lighting in the entrance and the deep blue sky at dusk. There is a time of day, at dusk, called "The Blue Period." I think that when I first heard of this, I saw it described in French. In any case, once I knew the term, I look for it at that time of day. And here it is!