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Hey, noob here with a couple of questions.

-How close can I put my light above my plants, I have a 600watt lumatek system with metal halide/hps bulbs, in a secret jardin 150 grow tent. I may need to raise my reflector to the ceiling of the grow tent, its a hydrofarm radiant hood. Is this going to be safe??? thanks

Rule of thumb, place your hand at the level of your plant's canopy. If it doesn't feel too warm you're fine. There's no set distance. Get 'em as close to the light as possible without burning them. I have the same Lumatek as you but I use a wing reflector. My plants are about 38 inches from their bases to the light, and about 30 inches from the canopy. I have lots of circulation in my grow tent, so heat is only a problem on 90+ degree days here in SoCal.