Microscopy Cold Light Source Slow-Start/Preheat Circuit

I have this older soviet microscopy cold light/fibre optics source “ОБ” for MБС-10 microscopes. In order to increase the life of the 12V 75W halogen lamp inside I wanted a slow start circuit that first limits the current through the bulb such that the latter can preheat a bit before it goes over to full power. To accomplish this I built a simple NE555 timer circuit that switches a relay that bridges out a 2R7 power resistor that limits the current through the bulb.