a one hundred and eighty degree array of small inexpensive solar panels(very small) up to eight...coorisponding to sun position...when each individual panel is aligned with the sun it will create a charge greater than the rest of the array...therefore closing a low voltage relay switch coorisponding to that particular direction

as the sun pans across the sky each direction specific solar panel will align your parabolic dish  or photovoltaic array to that direction

and it would be really cheap to do