In order to image the first contact, it is better to know roughly the location of first contact. To avoid confusion, let consider we are viewing the Venus transit with binoculars and facing to the sun at about N70E. According to Hong Kong Observatory, the first contact location is at around 10:00 (assume the sun look like a clock). However when I use Stellarium and Safari, both simulations showed the first contact location at about 8:00. Any clue?
http://www.hko.gov.hk/press/D4/2012/pre20120523c_uc.htm