…continued10 Top Telescope Questions
4. Help! The Moon looks upside down in my telescope!
Yes, that happens. Or, in some telescopes, the Moon looks right-side up but mirror-reversed (flipped left to right). Don’t worry, nothing is broken this is perfectly normal. Since there’s no “up” or “down” in space, most stargazers just accept this optical quirkiness and don’t let it bother them. And, besides, you’ve seen this kind of thing before. After all, when you look at yourself in a mirror, isn’t the image staring back at you flipped left-right?
As a general rule, if your telescope’s optics have an even number of reflections (as is the case for Newtonian reflectors, like a Dobsonian), you’ll get an upside-down view. Scopes that have an odd number of reflections (refractors or compound telescopes, used with a 90° star diagonal) give a mirror-reversed view. If you’re not sure which case applies to you, just aim your scope at the Moon or a building and compare the view with what you see in binoculars or with your eyes alone. You’ll figure out right away what’s going on.