Once you can see it with the unaided eye, it’s way too late. We’re talking about a dark (read non-emissive) object, so you’re trying to spot a black dot on a black background. You’ll only see it occasionally if it occludes something or happens to reflect sunlight, which isn’t a given.
It’d probably be hard to miss even with the naked eye if it was close enough.
Once you can see it with the unaided eye, it’s way too late. We’re talking about a dark (read non-emissive) object, so you’re trying to spot a black dot on a black background. You’ll only see it occasionally if it occludes something or happens to reflect sunlight, which isn’t a given.