Timer for Microscope

This is another 555 timer based circuit I built to control an optical microscope used in one of our labs. The lab mates after using the microscope often forget to switch off the instrument which leads to replacement of the bulbs very often. To over come this problem I designed this simple circuit which would automatically switch off after a predetermined time (here 10 mins). The timing is determined by the following relationship
                                                                                     
                                                                                      T= 1.1 C1 R2

Tantalum type capacitor is recommended for C1 to avoid leakage and for proper operation.
Also, CMOS type 555 chip has to be used. Transistor Q1 can be any lower power NPN type.
VR1 should be adjusted to achieve desired ON time. Proper care must be taken when handling the mains side of the relay.