Which is "easy" for things that have present-day analogs, but somewhat more difficult for those that don't. And then there's the changes over the last 40-odd years (an "astrogator" in science fiction up to the 1960s would probably have used sextants and slide rules and a library of charts; today, it's a smartphone app more or less).You also have to understand exactly what a specific job entails, responsibilities, and how much time and when you spend doing it.