Equatorial platforms for dobsonian

Hello,
I am interested in building or purchasing an equatorial platform for my dobsonian. Can anyone give me any information on resources for building a dual axis equatorial platform? Is a dual axis necessary for photography or will a single axis work?
I plan on taking shorter exposures -less than 3 minutes with my digital camera. Any information will be appreciated.
Thanks.
Jay

Thanks for the post-very informative.
Jay