Hps

I have a 150w HPS over just one plant... how far away from the plant does the light need to be??

i have mine, about a foot away with a fan blowing. put your hand above the plant, and if its to hot on you, it will be to hot for your plant

Start with 18" above and wait 2 hrs and look at leafs. If they are streching up lower 2 inches and check 2 hrs later.
If leafs curl in TOO Hot raise up 2 inches.
If top leafs turn pale, then lights are bleaching leafs, raise 2 inches and watch.