These images taken with a Nikon D90 (18-105mm)
at f8 - 40sec - ISO - 400.
At 30 secs (or 75% of the exposure) simply manually twist the zoom lens to achieve the zoom effect.

Nikon D90 Raw image processed in Adobe Raw Converter - firstly for the sky and then for the foreground and blended in Photoshop. (click for larger image)