Just a quick note here on determining pinhole diameter: If you have a flatbed scanner it's pretty easy to scan the pinhole at a known resolution and figure out the size of the pinhole from the circle that you see on-screen. This can be helpful information when using pinhole exposure calculators.

Although you know your needle size, if the needle moved at all in the horizontal direction when you made the pinhole then you really don't know the pinhole size without measuring it. I've used the flatbed trick for years and it's helped me a lot.