Again we have one of those threads that includes a reply (Mark's) that amounts to invaluable information and advice for anyone wanting to get into this sort of photography.
I'm saving this for future reference when every anyone asks the questions.
Just as an aside, or an add-on comment, some of have this week, being discussing an App that's available for Android, for Canon users, called the
DSLR Controller. Through tethering an Android Phone of Tablet to the camera, this app can act as an intervalometer.