Prettyphoto how to open a specific image using api

I use this example from the documentation:

api_images = ['images/fullscreen/image1.jpg','images/fullscreen/image2.jpg','images/fullscreen/image3.jpg'];
api_titles = ['Title 1','Title 2','Title 3'];
api_descriptions = ['Description 1','Description 2','Description 3']
$.prettyPhoto.open(api_images,api_titles,api_descriptions);

For example, how can I make image number 2 in the array the starting point when prettyphoto opens, so it can also go back from that point? (I could place it first in the array, but then I mixed my content)