Re: Lighting Specs

In a message dated 96-02-21 16:17:59 EST, Dirk  wrote:

>Also, I know I've read about it somewhere, but what does the "degree"
>designation mean when applied to bulbs.

I've been doing a lot of studying of this in the last few weeks. The "degree
Kelvin" refers to the chromaticity of a light source. Quoting from a brochure
from G.E.:
 "As a piece of metal (or a theoretical black body) is heated up, it changes
color from red to yellow to white to blue-white. The color at any point can
be described in terms of the absolute temperature of the metal measured in
kelvins (K). The progression in color .....is called the black body locus.
The color can now be specified in either x,y cordinates (C.I.E. Color
Triangle) or more simply, in kelvins on the black body locus.
Lamps, other than incandescent, which typically do not have a smooth,
continuous spectrum, can also be specfied by the color temperature or kelvins
represented by their x, y location. This is called correlated color
temperature (CCT). Two lamps, one plotted above the black body locus and one
below, could have the same CCT. However, the one above will appear green, the
one below pink. Color temperature is not really very precise, except when
specifying the chromaticity of incandescent lamps." 

So although the aquarrum industry likes to quote these numbers, in reality
they alone tell only a little about the bulb. Someone who is more versant in
spectroscopy could tell you more about how this works. I do know from the
literature I have in front of me. Sunlight at sunrise is 1800K, at noon it
has a chromaticity of 4870K and the Northwest Sky has a chromaticity of
25,000K. I also read somewhere in my research on lighting that the sun has an
average lumen ouput of 100K lumens. Compare that to a 175W MH with a
chormaticity of 5200K and mean lumens of 9000. 

Sorry, if I'm getting long winded, but I've been doing a lot of research on
this for myself and couldn't resist sharing what I found. This all started
because I wanted to build a DIY lighting system for my aquarium and didn't
like the prices in aquarium stores.

If this is all very confusing, don't feel bad, I'm still somewhat confused.
What I have discovered though is (4) 110W VHO lamps (total 440W), daylight
spectrum, will put out 19,800 lumens compared to 24,400 mean lumens for a 400
W MHD. I don't know how the heat output would compare, though I suspect the
difference would be considerable.. Personally, I'd choose VHO. It seems less
expensive and less a problem for heat buildup. Lumen per watt are comparable
and the fluorescent ballasts should be less expensive, providing you don't
buy them through Aquarium suppliers. I have even been able to find the part
number for Super Actinic and Actinic bulbs (not VHO) in the Philips Catalog I
have. They claim they're exclusive products. (?)

I hope this message is enLIGHTening. :-) Feel free to e-mail me if you have
questions. If I can't answer, I have a friend who can and will help me find
the answer.

PacNeil at aol_com Neil Schneider