[DoctorBeaver (OP)]

I was out in the garden a while ago just looking up at the night sky. I could see stars just off-centre from my line of vision; but when I tried to look directly at them they either appeared much dimmer or I couldn't see them at all.

Why is that?

[RD]

The non-uniform distribution of sensors in the retina cause the phenomenon you have described.
http://en.wikipedia.org/wiki/Averted_vision

[DoctorBeaver (OP)]

Thank you, RD, that's very interesting. I'm obviously right-eyed as I can see the faint stars better when I look slightly to the right. I'll try the up/down trick next time there's a clear night.