Here's looking at you, kid (part 2)

Next we need to calculate the number of amateur or hobbyist astronomers. Earth has 6 billion people and let's use that number as a sustainable population of each of the three civilizations. Now, like here, not all populations are equal - many people do not have the resources to purchase or build an amateur telescope. And whether a civilization can ever reach a utopian state where all are "wealthy" (have spare time and resources), we cannot know. We certainly hope so, but for this calculation we will stay with conservative estimates. So, let's use the population of earth and its number of amateur astronomers as a basis for the estimate. Taking Albuquerque as an example, there are roughly 300 amateur astronomers in a population of roughly 500,000 residents - thats a factor of 0.0006 for our calculation. But not all cities on earth have the same standard of living. Assume the Albuquerque level of resources, or higher, represents only 1% of the population. So 1% of the 6 billion have the resources and time for amateur astronomy, and 0.0006% of that number actually is interested in the hobby.