I have the key and focusing crystal. I got the key from a room that had a shocking dwarven spider. Is this the wrong key? Where's the correct key to get in the oculary? Thanks!

It's at the end of a long hallway, theres an auditorium near the end. You will see a bunch of dead falmer but no enemies, until you find either a dwarven steam centurion, or a centurion sphere. The key is in one of the chests in that room, there should be a bunch of dwemer scrap laying about as well.

Make sure you make another save before going in, that quest can be buggy.

like the other guy said there is a hallway and its easy to pass up but if you don't have the key, just go back and you'll find a door you didn't go through, its not too much before where you need the key.

I had already found that hallway but overlooked the chest. I finished!! Thanks all!