You can use interval shooting with this pic circuit Preview
Some camera contains „interval shoot” programme. You can set the shutter time and the bulb time. After the counting down, (you can set it from 1 sec to 99hour, 59minute, 59sec) , the shutter is activated. You can set the Bulb time from 1sec to 59minute and 59sec. Some site cal this circuit „Intervalometer”.