If you are doing a short-term project and using the camera timer, set it to record at the appropriate interval. Please refer to page 4 of the Quick Start Guide for specific instructions on using the timer feature.
Remember, the camera can store a maximum of 53 images at a time when the camera is on economy mode. If your think you will need more than 53 images for your project, change the capture rate of the timer, by increasing the interval. If you think you will lose too much of the event you are trying to record, consider using a video camera if you have access to one.