Photo by: ESO Creative Commons What do Christian Doppler and Albert Einstein have in common? Simple, they are both instrumental in weather forecasting through their contributions to the information people know about radial velocity. Without understanding how radial velocity works, warnings about tornadoes and hurricanes are not possible.

Photo by: Tamasflex Creative Commons If you recently have had a conversation with an astronomer, then you’ve probably heard them mention the exit pupil as a certain eye piece in telescopes or binoculars. But what does exit pupil really mean, and how can it affect views when looking through a telescope?