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Re: [APD] Re: Lighting

--- Daniel Larsson <defdac at hotmail_com> wrote:

> > . . . the results
> > don't (might not) quite tell us which bulbs are best
> > because there are some unavoidably large
> underdetermined
> > assumptions . . .
> 1) What are those assumptions? Help me make the
> calculations 
> better!

Some of them are

what ballast is used -- the standard ballast the
manufacturer used for the ratings?

Are the ratings based on an input of 110VAC, 115VAC,
117VAC, or 120VAC? It won't matter with some electronic
ballasts but it can matter a little with heavy core

How much burn-in? The light output decreases over time and
not all manufacturers use the same amoumt of burn-in time
as the reference period. In fact, some use a time way out
there and then say *their* bulbs never dim below the rated

The average ambient temp.

The manufacturer's tolerances/quality control. The stated
rating is an average of samples from a production run but
the run you buy from might be very diff, especially the
cheaper bulbs.

Whether the phosphors in a particular make of bulb
deteriorate with a resulting spectral shift with use. The
older VHOs were sort of nototorious for this. The higher
quality versions of newer design power compact
fluourescents, not so much.

With some imagination, we can think of others. 

I don't know the actual values to replace these tacit
assumptions so I don't know how someone would work them
into the calculations to improve them. They underdetermine
the results -- how much? Who knows? But not knowing doesn't
make them irrelevent.

Are some bulbs better at shining PAR? Sure, but I wouldn't
split hairs trying to find the best. That's a personal
approach, but I'd rather find out how Karen's aquaria do so
well with whatever lights she uses than try to finesse my
own skills with bulb selection. I usually just buy AHS and
know I'm getting a darn good lamp.


Plant your feet in Washington, D.C. and touch the moon -- at the National Air & Space Museum. 
And learn the art of aquascaping Senske style at AGA2K4. 

Speakers, field trip, Ray "Kingfish" Lucas, and more. . .
The Annual AGA Convention, 2004, November 12-14.

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