center image captions

Although I have images centered, the caption won’t center. Here’s the code:
[caption id="attachment_120" align="aligncenter" width="750"]<img class=” wp-image-120″ style=”border: 2px solid black;” alt=”Melchers_Dig_HCAA” src=”http://hcarc.hcarcheology.org/wp-content/uploads/2014/02/Melchers_Dig_HCAA.jpg&#8221; width=”750″ height=”563″ data-id=”120″ /> David Mechler, Steve Stoutamire, Ed Rendon, Cleste Hall, Kay & Woody Woodard[/caption]

Any ideas?