Big reflector small source, no big secret.
Parabolic reflector, parabola has a tiny point of focus where every thing will be reflected out in a parallel beam, outside the focus point it will go a bit this way or that.
WW2 carbon arc searchlights, 6-8` diameter used two carbon rods and a point of light less than 1/4" in diameter. Kick sand in face of skytrackers ;-)
Skytracker et al, use xenon light sources, this is a very short arc lamp allowing most of light to be collected by parabolic mirror and thrown out front parallel.
http://members.misty.com/don/dschlamp.html#dlsphid
Typically 2.5Kw to 7Kw lamps.
www.skytracker.com
www.spacecannon.it
Tungsten saource is a bit big, so need big reflector.
HTH
Adam