Decay in Artificial Light Sources

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Decay in Artificial Light Sources

Post by Richard Sext » Sun, 16 Oct 1994 12:54:35



This opsting has nothing to do with Orchids, Bonsai or indoor gardening.

What it does outline is the dramit decay in light output of bulbs over time.

The decay is even worse than the manufacturors already dismal projections.

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Quote:


>> 55 G tank
>> 2 175 5500K MH bulbs
>> 2 40W Actinics

>> The lgihts are about 8 inches above the water surface, situated in the center
>> of the two halves of the aquarium.

>> The readings at the water surface below the bulbs was around 20,000 Lux. (one
>> bulb is new and the other is over a year old).  The light below the old bulb
>> was about 18,000 lux.  

>At 13" from the surface, a new bulb (2 hours old) read 19,900 lux and a
>year old bulb read 9,900 lux.  The new bulb after 2 days read 17,100 lux,
>after 16 days 15,700 lux.

>> At about an inch from the new bulb the reading was 101,000 lux.

>2" from the a new bulb, the readings were 126,000 after 10 minutes,
>110,000 after 4 hours, 102,000 after 2 days, 90,000 after 21 days,
>60,000 after 315 days.

>> I was surprised at the difference in reading between the surface of the water
>> and the one right at the bulb.

>Since the bulbs are close to a point source, the intensity ratio is approx.
>1/distance^2.

>> Out of curiosity, I took the light meter outside the house and checked it
>> around noon with the sun shining on it.  It read 140,000 lux.

>I think I measured 125,000 one random day here in Ft. Collins, CO.

>> I don't know what to make of these readings, or know how accurate they are.  
>> But just thought they may be interesteing to some readers.

>They look good to me :-).

>> On a side note: My experimetental plant tank, with 2 new Pen Plax Ultratrilux
>> and one Sylvania grow light (2 ft. tubes) read 14,000 lux at 3" from the bulbs.

>I read about 14,000 lux at about the same distance with Tri-lux bulbs.

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