Peripheral vision
Retinal light receptors are unevenly distributed. In the center of the retina (the fovea), there are mostly cone photoreceptors. Cones are used mostly for color vision, and don't pick up on dim light. (This is why you can't see the colors of things in a dim room.) Rods (for black and white light) are highly concentrated in our peripheral vision, and are very sensitive to dim light.
So you can see dim stars in your peripheral vision that you wouldn't be able to see if you were staring right at them.
The eponymous conference is next Wednesday.