Lighting Lighting height for MH bulb?

[Surfer Joe]

I have some seedlings under a 400W MH light in an air-cooling reflector. How high should the light be to avoid hurting them but also to keep them from stretching? I currently have it set about 30 inches above the plants. My hand feels very little warmth even a foot away from the light.
Thanks for any advice.

 

[swampman]

I Keep.My 400W HPS around 18 in in Veg ...,then12 or as closeas I can With out My Hand Burning ...

Cheers bro

 

[SkatterBrayne]

My 600w is air cooled, and 6" from the canopy. Distance is largely dependant on heat (although you will light bleach them if you get much closer than 6". Keep them as close as you can without causing heat stress. Measure the temperature with the back of your hand

 

[Surfer Joe]

Thanks. I will try lowering the light a bit.
I am amazed at the hydro grow method.
The plants are only a week old but are almost twice the size of another plant of the same age that is planted in soil.
That's why I am worried about the light distance if the plants get too tall for the tent. I figure that I have a little over a meter of height from the tops of the buckets to the highest that I can place my light in the tent.
I am looking into a little lst to bend the main stem over and keep the plant a little shorter as it grows.