Date: Fri, 26 Sep 1997 12:17:32 -0500 (CDT) From: Paul Burkhardt <burkhard@aries.scs.uiuc.edu> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg3725$foo@default> Subject: Re: Artificial Light
Matt <drake@erols.com> wrote:
> In light of (bad pun:) the recent questions regarding artifical
> lighting, I can tell that my experiences using two shoplight fixtures
> with 2 Cool-White Flourescent tubes apiece (a total of 4 tubes), the
> tubes being 4ft, 40 watt each, that they seem to not only fail to put
> out enough lumens to turn any CP reddish, but also do not provide the
> full spectrum that plants require (cool AND warm spectrum).
I've found that a 30 watt normal fluorescent turns my neps and droseras
red. Perhaps you've got yours too far away from the plants. Also, there is
no cool and warm spectrum of light!
> However, I am currently interested in purchasing a Metal Halide
> lamp or a High-Pressure Sodium WITH the Agricultural bulb to provide
> full spectrum (High-Pressure Sodium without Agricultural bulb is
> limited to the warm spectrum). The cost of such artificial lighting
> runs around $200 + $80-$100 for a cooling unit. Prices for HPS with
> the Agricultural bulb can run $300 + cost of cooling unit.
This is quite expensive, and it would still be inferior to natural
sunlight. Depending on what you're growing and where you live, you
probably don't need to pay that much for artificial light.
> By the way, don't buy incandescent grow lamps or Halogen lamps or
> any other inefficient, heat producing, expensive lamps that don't put
> out enough lumens, and most of the time not even in the right spectrum
> (in the case of the Halogen).
Where did you get this information? Incandescent lights are more similar
to blackbodies (full electromagnetic spectrum) than any others, meaning
they produce a wider spectrum of light than fluorescents and vapor lamps.
The problem is a large majority of the intensity is coming out in the
infrared region. Also, the photosynthetic active region for plants is in
the visible region of light, thus you would want to get a light that is as
'white' as possible. Incandescents, and halogen lights can provide the
necessary frequencies, but the problem is in the intensity of the output,
and per watt per price, fluorescents are the best.
Paul Burkhardt
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