If you're just trying to see all the objects, then yes, N^4. But if you're trying to figure out whether they're planets, you need to either resolve disks or ta

If you're just trying to see all the objects, then yes, N^4. But if you're trying to figure out whether they're planets, you need to either resolve disks or take multiple observations to observe motion. I don't have a good feel for how the latter scales with N in practice...