Measuring Florescent light output

[naoki]

Steve, my phals and paphs grow well with around 800-1000fc for 15 hours. They are in a grow tent, so they don't get any ambient light. At one point, I made a following calculation (I posted it to one of the forum, but I can't remember): the cumulative amount of photosynthetically active radiation (PAR) from this setup is roughly equivalent to that of natural sun light with 1200-1500fc of peak intensity (this kind of "peak intensity" is the type of values used for "recommendation"). I grow only species, so hybrid phals may do ok with less light.

If you are using T8 (32W for 4'), then you want to put them within 2-5 inches. If your grow space is about 1'x4', you probably want to have 4 bulbs (2 stoplights). If you are using T5HO (52W for 4'), then mine is about 7-10 inches from the top of the leaves.

In the summer time, I may need to put them further to prevent heat related problems.

I don't have much experiences with growing Cattleyas under lights, but my 3 rupicolous Laelias are growing well (they are still too small to flower) about 4 inches from T5HO (I think it's getting around 1600-1800 fc). I don't know if they will flower if you are using T8, and T5HO may be better. If you can put them outside during the summer, T8 may be enough for the winter.

I posted some measurement of a T5 fixture, but is it for 2' unit and not 4' unit:
Big Leaf Orchid forum • View topic - 2' 1 or 2 bulb T5 Fc question