Simply I need to calculate the torque required to move this solar tracker in the attachment assuming that i know every part's weight. What is the criteria should i follow?

Estimates of friction at all joints, Rate of acceleration desired as it starts up. What loads does wind have on the structure? Hint start with a free body diagram...……..

A practical way to calculate the magnitude of the torque is to first determine the lever arm and then multiply it times the applied force. The lever arm is the perpendicular distance from the axis of rotation to the line of action of the force. and the magnitude of the torque is τ = N m. http://rxmarine.com/Natural-Blue-Biodegradable-Cleaner-Degreaser