Eric Reitan on Metaphysical Naturalism: "...whatever scientists discover, through whatever methodologies they employ, will never be an understanding of reality itself. At best, science will be the project of describing in painstaking detail the world of appearances (what Kant called the empirical world) and constructing helpful conceptual models for engaging with it in ways that, we might say, decrease the frequency with which we are surprised....'
"Kant calls the world of appearances “empirical reality”—it is real in the sense that it’s a given, something we have to come to grips with. But even though space and time are therefore “empirically real,” they are not, for Kant, a feature of things as they are in themselves apart from our experience. They are, rather, the necessary form in which our faculties of perception present objects to us in experience. Kant captures this idea by saying that space and time, while empirically real, are transcendentally ideal."
That is about the most concise statement I have found yet of how Kant was an empirical realist and transcendental idealist. So Kant wouldn't say that 'the moon doesn't exist if there is nobody to perceive it'. He was an empirical realist. But how the moon exists 'in itself', unperceived by us, we don't know, and will never know.
Finally an observation from the same series of articles on 'the noumenal self'
Quote:...it is possible to simply be—to become quiescent, if you will, and simply be what one is rather than attempt to know what one is.
And in this place of cognitive stillness, one discovers in a direct experiential way an ultimate reality that cannot be conceptualized or made into an object of study. This is the domain of mystical experience—and even though it is ineffable (that is, even if it cannot be made into an object of knowledge) it brings with it a kind of insight or enlightenment. One may not be able to adequately put this experience into propositional terms that can be affirmed as true, but that doesn’t mean one hasn’t in some sense encountered noumenal reality. One hasn’t encountered it as an object of experience (since that would turn it into a phenomenon). Rather, one encounters it in the way one experiences.
- emphasis added.
This is the point of meditation - to go back to that state of stillness again, and again, and again, until you gradually begin to realize what it is you are seeing, and who is seeing it - which are one and the same.
Heineken Grolsch 
