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Kenyon, Mn.

I have my starts under a 400 watt, metal halide grow light, the distance is 22 inches from the tops of starts to the bulb, too far? too close??

5/3/2004 9:12:58 AM

[email protected]

Check the temperature at 22" & post.

5/3/2004 10:20:50 AM

Walkerton Ont

to far away. if they are too far away they will get long and stringy. Its ggood to have them away from the light like 2 - 3 inches. dont have them too close or you will burn the plant leaves

5/3/2004 10:40:24 AM

Montoursville, PA

Cold use the back of hand test. If you feel heat you are to close. Back off until you feel no heat.

5/3/2004 10:46:37 AM

Western Pa.

I think if you have 400 watts , 2-3 inches is too close. Hang the light on a chain, and you can experiment by slowly moving it down. If the leaves start browning, take it up some! My 1000 watt will fry leaves at 2'!

5/3/2004 11:08:07 AM

Kenyon, Mn.

Tremor, Temp taken at same level of plants reads 74 degrees,Doc, Back of the hand test, well I LIKE the heat, warm, but not hot, course I only had my hand there for about 2 minutes, Kilr , I agree with you, my 400 watt will fry other plants at 3 inches, the light is on chains, keeping constant survielance, but gotta go outside.....sometime! LOL

5/3/2004 12:13:31 PM

Walkerton Ont

i said it depends, i have one grow light and one cold light
they are about 2 inches away from light, no problems
you could use both light bulbs as cold and the plants will still grow

5/3/2004 12:15:38 PM

I'm with Gordon... GO UTES!

I would ditch the high power lights and go with low power
flourescent bulbs. This way you can get the seedlings close
without worrying about frying them. Two to three inches is
the distance you want.

Light intensity falls off by the
"distance squared". That is, at twice the distance, light
intensity is "one-fourth" as intense. I realize you're getting
more light out of the metal halides, but at 22 inches vs.
2 inches, you're getting much less to the plant. (At least
if my math is correct...)

With the flourescent bulbs my plants turn a very rich green
color and stay very stocky.

Regards, Cliff
http://idahopumpkin.tripod.com/ (updated today)

5/3/2004 12:36:16 PM

Western Pa.

I like my wattage like my women, the bigger the better!
(only kidding!) MORE POWER! Argh, Argh, Argh! I like it INTENSE!

5/3/2004 2:34:54 PM

Cornwall UK.(50N 5W)300ft.

22" is ideal for my 400w sodium bulb, metal halide give off more heat but you shouldn't be to far out my temperature goes up to 90* when the sun shines in the window with no problem.If you think it is getting to hot consider putting a cool air fan between the plants and the light.

5/3/2004 2:36:19 PM

Deer Park WA

We use two 2-bulb flourescent shop lights, each fixture has one cool white 40 watt and a "Growlux" 40 watt grow light bulb. I like the combination as it seems to enhance the spectrum. We have them on adjustable chains and keep the fixtures about 2 inches from the leaves. Like Cliff said nice green, stocky seedlings.

5/3/2004 3:26:26 PM

I'm with Gordon... GO UTES!

That's fine, you can run the hot lights... but comparing
2 inches to 22 inches, you're getting somewhere between
1/64 to 1/256 of the effective light at 22 inches, compared
to 2 inches. Like I say, you can do the hot lights, but
I thought the point was that the plants were getting leggy?

If they're not, more power to ya! (Sorry about the pun.)

Regards, Cliff

5/3/2004 3:36:49 PM

[email protected]

I think the light loss equation being used assumed the lumens output is identical. It isn't. The HPS & Halid lamps crank the lumens out. So starting out so high, the loss at 22" could still be more intense than flourescents. Phillips Lighting has a website dedicated to this stuff & we bantered it around a while back. Try a search of this website for "Phillips". You might find it.

5/3/2004 3:45:04 PM

Cornwall UK.(50N 5W)300ft.

400w HPS gives off 50,000 lumens.
40w flourescent gives off 3,600 lumens.
12.5 w at 2.75 ins is the same as 400w at 22ins.

5/3/2004 4:10:17 PM

Canada

Myself i'm just useing regular "GROW BLUB'S 2 florescents
they are ment for growing unlike the regular "white" florescent bulbs and i keep my plants roughly 6" away from the light i keep the sides and bottoms of my pots heated with heatrocks and they get a bit of warmth from the bulbs themselfs and they seem to be growing very well!!

5/3/2004 5:28:26 PM

I'm with Gordon... GO UTES!

One would need 121 times more light at 22 inches vs.
2 inches. Whatever, I'll take my power bill! ;-)

5/3/2004 5:29:58 PM

Kenyon, Mn.

Wow Guys, Thanks for all the responses! Tell Ya what I'm going to do: In My basement I have a White 4x8' table, at one end of it is the 400 watter, the other side(I have the sides seperated with 1" thick (white) styrofoam) is 6 4 ft. flourescent fixtures, each have one Daylight and one cool white bulb. I will move 1/2 of them to the flourescents. No Cliff I wasn't having a "leggy" problem, sorry if I mislead you, as far as Light loss, I have the area WHITED OUT!
AXC, when I read your suggestion I thought..DUH, guess I could turn on the fan..(mounted at the edge of table!! I just want the "best" for the Babies, right now the stem is aprox. 11/2 inches(comments?) Thanx again :<}

5/3/2004 6:08:54 PM

Western Pa.

I used to use 4- 4 foot florescent bulbs in a window facing South and still got leggy seedlings no matter how close I put the lights. I may "lose" a little light, but by placing foil or anything white around all the plants(as Bumpy mentioned), much is reflected back.I have nine full flats of flower and veg. flats as well as AGs, all under one light. I've also grown plants all winter with my metal halide, and I don't believe I could have with 4 florescents. I've never burnt any leaves either(except on 'maters!)

5/3/2004 10:06:37 PM

Montoursville, PA

Duh.......Planted seed 20th. Emergence was three and four days say the 23rd. and the 24th. First true leaf showed 27th. Planted into cold frame 28th. Three and a half days under white florescents....no leggy plants....no pot bound root bound seedlings. The two back up seed were planted four days later to avoid the leggy situation. I will plant a few every three or four days to back up new growers we have near us this year. Otherwise my original two back up plants would be trash by now.

5/3/2004 10:22:06 PM

[email protected]

My lighting set up is pictured in my diary. Here is the address..

http://www.bigpumpkins.com/Diary/DiaryViewOne.asp?eid=17813

I bought these clamp lights, and have 100 watt light bulbs in them, but with the reflective nature ofthe domes, I get a lot of lumens to the plant. I keep the bulb on average nearly 6-8 inches from plants. Lineup aint bad either!

5/5/2004 9:11:37 PM