TAG
telescope
Two and a half millimetres of light: a phone at the telescope eyepiece
A disc of light 2.5 mm across floats above the eyepiece, and the camera has to sit inside it. The arithmetic of scale, brightness and alignment.
Jupiter is three pixels wide: shooting the planets with a phone
On your phone's telephoto lens Jupiter covers three pixels. The real numbers, afocal shooting through a telescope, and the two minutes before it rotates.
