With the days as long as they are, I thought I would do a little research on twilight. No it is not the books and movies about Vampires, but rather the actual phenomenon of twilight.
I was surprised to learn that there are three different twilights!
After the sun sets, Civil Twilight occurs a short time after when sun is between 0 and 6 degrees below the horizon. This is named as such because it is still light enough out that “there is sufficient natural light to perform most outdoor tasks without artificial lighting“. I would assume that there is no need to put on streetlights on during this period.
Nautical Twilight occurs occurs when the sun is between 6 and 12 degrees below the horizon. If you are a sailor, then you can still see the horizon with a naked eye (ie. the dividing line between the ocean and the sky). We really can’t see this here as we have the beautiful mountains in-between. But I can understand how this would be important for sailors.
Astronomical Twilight is when the sun is between 12 and 18 degrees below the horizon. This twilight “marks the boundary between a slightly glowing sky and a perfectly dark canvas“. This is important for astronomers if they want to examine faint objects in the sky. A really fun fact is that at our latitude here on Seaview, at this point in the year, we never leave Astronomical twilight in the summer… meaning that the sun does not go below 18 degrees and therefore there is no ‘true dark’ time during the night. But this is due to return soon on July 11th, were we will start to get true dark in the deep of the night.
A special thanks to Craig Hoskins who, while looking over the ocean in the evening the other day, was talking about various types of twilights and inspired me to look this up!
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Glenn Moore
1412 Seaview
