How to use namespaces?

I’ve been using Ember for a few months now, but for the life of me I can’t figure out how I should be using namespaces. There seems to be a lack of documentation on this, and much of what I can find seems to be outdated.

What am I doing wrong in this very simple example? If I am to move ‘SecondController’ into the ‘App’ namespace everything works as expected. So I’m assuming this is because I am referring to the path incorrectly, but according this blog post I am doing the correct thing Ember 1.0 RC2

I understand you shouldn’t be nesting namespaces, I can’t even get non-nested namespaces to work. Thanks for any insight.