Dumb question..

Nafydad420

Well-Known Member
So I was looking at these charts that shows the optimal range you should keep your lights, and it says distance from bulb.. I know these charts are old so here is my question... I am using a cool tube and the bulb is 3 inches above the glass, do I measure the distance from my plant top from the bulb still or the glass?
 

Roger A. Shrubber

Well-Known Member
i'd measure from the tube then add a couple of inches for the space between the tube and the light.
that being said, don't rely on those charts too much. a quick test is to hold the back of your hand next to the top of your plants, you want to be able to hold it there for at least 30 seconds without it becoming uncomfortable. then keep an eye on it and adjust it over a couple of days, till you start to see it effecting the plant. that's your limit, back it off a couple of inches and you ought to be in your sweet spot.
 

Nafydad420

Well-Known Member
i'd measure from the tube then add a couple of inches for the space between the tube and the light.
that being said, don't rely on those charts too much. a quick test is to hold the back of your hand next to the top of your plants, you want to be able to hold it there for at least 30 seconds without it becoming uncomfortable. then keep an eye on it and adjust it over a couple of days, till you start to see it effecting the plant. that's your limit, back it off a couple of inches and you ought to be in your sweet spot.
I've had it 16 inches from the glass, or (19 inches from the bulb) just moved to 16 inches from bulb, 13 inch from glass. Sound Okay?
 

Roger A. Shrubber

Well-Known Member
that should be in the general neighborhood, watch for leaf edges to start curling up, if they do, move it a couple of inches farther out.
i have a small fan blowing between my cooltube and the tops of my plants, helps keep the canopy temp down a little.
 

Nafydad420

Well-Known Member
I do the same test but i hold my hand for at least a min

You can "feel" how intense the light is.

If its too hot like rodger said raise em. :)
I'm not sure about that test... with my cool tube I can place my hand to within 3 inches of that glass and it's not hot or uncomfortable...
 

Cold$moke

Well-Known Member
If you hold it there you should be able to feels the rays on your skin like being in the sun.

If it absolutely positively doesnt make your skin uncomfortable after a whole min then

You can place your light at what ever hieght you want then just look for bleaching and leaf curl
 
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