A device for the registration of beam positions of an extralight torsion balance is developed, mounted and tested by practice of astronomical observations. The device allows the observational process to be completely automated under the constant monitoring of measurement results in real time. The principle of colour division of stationary markers setting the meridian direction and a mobile marker is used. For this purpose, different luminescent paints and an UV-radiation source are applied. Unlike other registration systems of this kind, the device described enables one to minimise convective air streams inside the torsion balance chamber and to raise essentially the automatic reading accuracy for a beam position. An error of individual determination is equal to ±0.172°. Long-term observations performed with the device allowed us to reveal a clear-cut daily cycle the nature of which remains to be clarified.