I know that this has caught more than a few of us out before.
If you want to learn more about Mercury Vapour or Metal-Halide light sources, click here
and ask any question that you like.
Surely between the bulk of us we must be able to help one another out.
I work with Street-lights a fair bit, I can help.
Or any light source for that matter, we are her to learn.
Let's face it, these days if you're not young, you're old - Red Green