-Paint the inside of the box you are using black; help stops light leakage through thinner card and stops light bouncing around inside.
-Foil is not a great substance for making a pin hole out of, it's thin and when you stick the pin through it actually rips the foil rather than making a clean round hole. The objective is to make it as round a hole as possible to get the best image. The best results I have seen involve a thin piece of sheet metal, rather than poke a hole you hit it with a round metal stamp or punch that doesn't punch through but makes a small round bump in the metal. You then sand the bump with fine sandpaper to get a very round hole.
- Without a lens the light coming through the pin hole is very weak, so it needs to project into a dark or shaded area, the darker the better. Best result come from a traditional Camera Obscura; a darkened room with the pinhole letting light in. This is utterly impractical with something like the transit but we managed to turn a Photography darkroom into a massive Camera Obscura when I was in TAFE using the noticeboard pinhole in the door. (We also did it with a classroom and I have seen someone make a pinhole camera out of a PeakingDuck)
Just some tips, maybe too late but you never know...