Measuring Florescent light output

[The Peloric Orchid]

I strongly recommend buying a lux or footcandle meter. I got one for around twenty bucks on Amazon (just remember that there's around 10 lux per footcandle). That way you can take the guesswork out of light placement. The main downside with these kinds of meters is that they're calibrated to more sensitive in the green/yellow range, much like human eyes, so they won't measure colored light accurately. The alternative is to buy a PAR quantum light meter, but these are much more costly and there's less data about orchid growth in light levels measured in micro einsteins.