In addition, there is a notion of "photometric nights" which include, among other requirements, Sun being at least 24 degrees under the horizon. These conditions are necessary to conduct precise photometry, because an extremely tiny amount of scattered sunlight still makes it through when sun is between 18 and 24 degrees. So in a way, we can add "photometric twilight" to the list, although the number of people who are affected worldwide will probably fit into one big room.