help needed

Greetings fellow growers i have some doubts in my head and i bet you can help me out.what is the corect distance from 600w grolux hps and seedlings????and do i lower the light as the plant grows to get more lumen or let it grow towards the bulb?? I am using a cooltube also and my current seedlings got strecy and i don't want that to happen next time so i need your help.
I know a Mh bulb would be better but is not an option right now.
My plants are now 15 cm tall and i plan on flowering them next week my cooltube and 600Watt lamp is at 90 cm( 3 feet) from the plant must i lower or raise them or just raise the lights when the plants get too close?
i am realy high right now hope that made some sense i would really apreciate any help.All the best S.

hello... I'm also a noob, but from what I understand, 3' would be way too far away... Maybe about 12" but that's a guess on my part. Hope I'm not just confusing you. Sorry.

they got this cool new website out..hang on let me think of the name..oh yeah google..try there

K bro, Ima make this real ez for you. You will be able to get it close since you have a cool tube but here is the easiest way to tell how close you can bring your light. Just put your hand a the top of your plants canopy and see if it gets too hot for your hand, if so then your light is to close. If you can hand can stay at the plants canopy comfortably, then the plants can grow comfortably to. But when they are young Id keep it a good 18 inches away.