How high should I keep my light

Hey gang, I have a Sun System HPS 150 and I was wondering how far away from the tops of my plants I should keep the light from. Also I had read somewhere that you can use MH bulbs in a HPS system, if so what MH bulb do you recomend for the HPS 150?

if u can use a mh bulb use 1 of the eqivalant wattage or less. get ur light as close as possible without burning ur plants canopy. use ur hand to check if appropiate. put ur hand all flat underneath the lamp for a minute and see if it feels hot. if so raise lamps until correct temp is reached at canopy. my lights air cooled are about 1foot off the tops.. now if there seedlings be advised to keep the lamp more like 18'' to 20'' off em as to not burn them their dellicate.

id say 8 in but i dont really know how hot that bulb is, i like cfls my self. one way you can find out for your self is to put your hand under the light and find out how many inches you can feel the heat on your hand, as far away as you cant feel the heat or can only feel it a little is about where you want the tops of your plants

Thanks you guys, yes they are seedings about 6 inches and not two weeks in from seed to soil

Myriad86 said:

Thanks you guys, yes they are seedings about 6 inches and not two weeks in from seed to soil

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Do not listen to what that kaleo said, they dont know what they are talking about a mh is hotter than a hps and you dont ever put a hps 8 inches off your canopy. cfls you can get right close. Start with 18-20 inches like someone else said in this post i cant remember or i would credit them. Its simple really if there getting burned raise the light, once your comfortable with a height, play with it and see how close you can get without burning them, and then cut a string the length of the distance you found works best and tie a weight to one end and the other to your light and voila you will always know when to raise your lights

i keep my 1000watter a foot from plants.. air cooled tho.. i bet ya i could get a 150w hps down to 8 inches with air movement and no bleaching.. but nevermind the pissing match, keep the lights high enough to not wonder if ur burning them..