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  #21  
Old 02-16-2013, 02:49 AM
DTEguy DTEguy is offline
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A HO T5 bulb, on the other hand, with a 6400K color temperature, puts out about 100 and 90, respectively.
Is this roughly a universal PAR level for all 6400K-6700K T5HO tubes? Thanks...

Last edited by DTEguy; 02-16-2013 at 02:52 AM..
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  #22  
Old 02-16-2013, 11:23 AM
Andre Andre is offline
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I have a 8 bulb t5 fixture with 4 foot 54 watt full spectrum tubes. How close is too close (other than overheating plants), how far should I place my Catts. If they are very close (5 inches) do I only get the benefit of two or three of the tubes versus the benefit of all 8 tubes. I grow Catt. walkerianas, and nobiliors. They are not booming but some of them have a suntan. Tubes are on for 13-14 hours.
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  #23  
Old 02-16-2013, 12:25 PM
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Is this roughly a universal PAR level for all 6400K-6700K T5HO tubes? Thanks...
No.

First of all PAR is the sum of the photons emitted between 400 & 700 nm.

Second, the color temperature is a descriptor of the spectrum, not the intensity of it.

And lastly, a fluorescent tube is not a black body radiator, so the "corrected" color temperature is meant to fool the eye - not the plant - into thinking it is looking at a black body radiator. If you get a decent plant light bulb, the chances of the spectrum being better for the plant improve, but again, that says nothing about the intensity of light emitted, or the actual spectral wavelengths.

---------- Post added at 11:25 AM ---------- Previous post was at 11:22 AM ----------

Quote:
Originally Posted by Andre View Post
I have a 8 bulb t5 fixture with 4 foot 54 watt full spectrum tubes. How close is too close (other than overheating plants), how far should I place my Catts. If they are very close (5 inches) do I only get the benefit of two or three of the tubes versus the benefit of all 8 tubes. I grow Catt. walkerianas, and nobiliors. They are not booming but some of them have a suntan. Tubes are on for 13-14 hours.
Sounds to me like you're overdoing it.

8 tubes x 54 watts x 90 lumens/watt = 38,800 lumens. I'd bet you could back that off to 18" or more with no issues, but you really should measure to be certain.
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  #24  
Old 02-16-2013, 01:25 PM
DTEguy DTEguy is offline
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Please let me rephrase my question.

When you said 100 and 90 energy units for Blue and red for 6400K T5HO, is this a common feature for all T5HO at 6400k to have a balanced blue and red output? Or are you referring to a specific brand which you read or measured?

Thanks.

Last edited by DTEguy; 02-16-2013 at 01:41 PM..
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  #25  
Old 02-16-2013, 05:17 PM
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No, I am not referring to any specific brand, nor am I saying that it is universally true.

If you look at the absorption spectrum of chlorophyll, you will find that the red peak at roughly 660nm is roughly 90% of the height of the blue one at 430nm.

A 6400K black body radiator will also have that same intensity ratio of those wavelengths, but will also have greater intensity in-between.

A plant light that is rated at 6400K corrected color temperature is likely to have emissions at those wavelengths that match those ratios reasonably well, while a 6400K CCT fluorescent not made for plants may not.
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