RCU Forums - Help Building a Timed Camera Trigger

I want to use a timed trigger on a 8+ megapixel still cam rather than a video camera. The project seems simple enough and I'm hoping a 555 IC will help me accomplish this. I would appreciate some input. I'm hoping to make the circuit small & light - so this is what I'm thinking of using - a 555 IC to create the pulse, an 8 pin opto-coupler for the relay (because that's what I have), and a trim pot to vary the current being fed to the IC so that I can vary the intervals of the pulse. I was thinking of using the circuit from this page http://www.thefintels.com/aer/cameratimer.htm and modifying it to suit my needs. (eg an 8 megapixel wallet cam). I'll need the circuit to pulse the opto-coupler about every 1.5 - 30 seconds for this project. Also since I need a light weight circuit I'm wondering what the minimum power source would be. Is there a way that I could build something using a CR2032 battery or similar? Seems easy enough, until I visit digi-key and they start asking which resistance is needed for the IC. At which point, I'm stumped.