With this "telescope" you can detect high energy cosmic rays with their direction. Two geiger tubes connected with a coincidence electronic circuit are assembled on a stick that can rotate. Two geiger tubes are used with circuits from Images SI Inc. The signal outputs of the two circuits are connected to the input of a nand gate 4011. The output from the nand goes to the trigger input of a 555 timer in a monostable configuration. The output of the monostable is connected to the PC interface provided by Images.
The picture on the left shows the wood stick with the two GTs held by alluminium U-shaped strips. The lower tube can be moved in different positions in order to reduce the capture solid angle. The stick can be rotated so it's possible to measure the cosmic rays frequency versus the zenith angle. In the first experiment I found about 10 coincidence counts in a half an hour, but I must make more measurments. In the right picture you can see the two counters and the third box with PC interface and the coincidence circuit.