Advice on lamp height

Hey all,

I'm a first time grower looking for some advice on how far away I should position my light from my plants. I have a 1000w hps with an air cooled reflector. I had my light hung about 24" from the top bud with an air temp at 66 deg. Can I lower my light to increase light intensity without risk of burning my buds? I've read that anything lower than 24" inches (with a 1000w lamp) can burn your plant, is that mainly from heat, or light intensity?

Put your hand at the top of the plant. Lower your lights. If its uncomfortable to keep your hand at the top of the plant then the light is to low and adjust until you can keep your hand there.

If your only getting to 66 degrees with a 1000 Watt HPS I would go ahead and get it closer to maximize light intensity since your ventilation seems to be doing the job pretty well.