I sometimes get customers new to astronomy who tell me they cannot see the Orion Nebula. When I hear this, I know it is a matter of operator error, since I can see this famous Messier object under the most extreme conditions.
Take the other night, for example. The moon was full. That's bad enough, but my observing site is even worse. From my suburban Chicago, brightly lit apartment complex, I feel lucky to even see Orion, let alone the Orion Nebula. Yuk! Still, I grabbed my Swift Audubon 8.4x44 820 and let fly.
I could make out the nebula, sure enough, though to an inexperienced observer it might look like some haziness around the stars in Orion's sword. It was there, though, full moon and lights, notwithstanding.