I know there is an interesting Pan & tilt from openelectronics but my project is to move (to pan only) the whole raspi and camera with its waterproof case (# 500 gr) It 's for an outdoor site. as shown here http://ed-venture.biz/outdoor-pice-the-raspberry-pi-camera-enclosure.html My purpose is to get the camera moving 1/5 of a degree each 5 seconds
Use a standard servo, like this one. You could probably just screw the servo horns to the bottom of the case (or hot-glue, or superglue, etc.).
Then you can run the servo's wire to the Raspberry Pi's GPIO pins and program it how you want it (probably use a Python Script). For help with that check out this forum post.
Servo's can do that, but you have to make sure it has enough range. Most won't do 360degrees. Servo's however require some addition circuitry, to make them stop moving. You don't want jerkiness, when taking photos. This will reduce power usage.
Alternatively use a stepper motor. You'll have more precise control angle of rotation. But unlike with a servo, you have to set the start position of the device, as a stepper will only move relative to it's current position, where as with a servo, you can just specify the angle.