Sunday night proved to be almost perfect, with clear blue skies and only a moderate breeze. That’s important, because a strong wind can blow the camera around. When that happens, the ISS/Shuttle that should register as a line in a long exposure can sometimes look all wiggly. Not in this case. In order to minimize any vibrations, I also locked the mirror up using the custom functions of the camera. When the mirror flips up, it can introduce a tiny amount of vibration. It might not register if you were shooting a long exposure of a still life, for example. But when you are shooting a needle thing light trail from space craft, it will show up as a series of bends, or sawtooths, in the line.