The "down n dirty" way I use is with photo resisters. Normalize the output, build a jig that has them looking up with about 15 degrees between them . hook them up to analog 0 and 1. Read the output every so often( whatever you want) ant based on the delta V between them drive a stepper motor in the direction of the brightest light ( hopefully the sun).
You can program a min brightness so that the whole thing rests during the night. Since you are going to be tracking from East to West, you can either count the steps and when the brightness threshold drops below minimum, then step back East that number of steps and be ready for the next day. You can also just leave things as they are and the tracker will track back incrementally the next day.
This eliminates precise stepper calculations since the tracker stops when the photo resistors both bracket the sun.
I,ve done this, it works, but you have to get creative in lensing in the sun as it travels far to the North during the summer and passes overhead of the detector. I used an arched clear plastic lens with light baffles around the photo resisters so that a narrow strip of sky was presents with an arc of about 60 degrees N-S
Have Fun