The second way is to adjust the aperture on the front of the Photocell. 1 is the most sensitive and 11 being the least. You can see a swirl on the face, that is what controls the amount of light hitting the sensor. Unscrew just a little, the screw in the middle and adjust it by turing it to match the red mark. It is usually set at 5, I set mine at 1.
The third way to adjust it is to go to the front panel and adjust the resistor. IT is a blue square box with a white plastic screw on the inside. First you want to turn to all the way counter clockwise to as far as it will go and mark that with a sharpie. That makes it less sensitive. Then turn it all the way clockwise until it stops and mark that. This makes it the most sensitive. Now turn it back counter clockwise until it is about center between the two and check it. I would caution not to set it too far clockwise, it may strain the system itself.