Best angle for CFLs to be placed?

So I'm trying to decide whether to place my CFLs horizontal, vertical, or halfway between (using a Y-shaped splitter to put two angled bulbs in a vertical socket). Has anyone done tests with light meters to see which way maximizes the amount of light hitting the plants below?

Also, I was reading the small print on the box for a CFL and it says that the lumen rating is based on a vertical placement with the base up, and that the lumens could be as much as 5% different with the base down. Weird?

horizontal is the best, but y'd will suffice

27.5 degrees perpendicular to the angle of the 3rd node.

bigv1976 said:

27.5 degrees perpendicular to the angle of the 3rd node.

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BaaaWaaahaaahaaaha.

Gastanker said:

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Very very interesting post. Completely opposite from what i would have thought. +Rep.

CFLs are actually designed to have a directional downward cast pattern. At least that's what GEs light graph shows. If you look closely at most CFLs you can see that the tops of the coils are actually thicker than the bottoms. Although take those numbers above with a grain of salt as the reflectors are drastically different sized/shaped.

Here's GE's cast pattern for a 23w CFL (EL23R).



Small image but it clearly is directional to a degree.

For reference here is an HID in a reflector -

Thank you for the detailed response, Gastanker! I think I'll alternate large (42w) single vertical bulbs and smaller (32w) y-split bulbs, so that I get a wider coverage in the canopy.

I have had great success with keeping lights at 90 degree angles under aluminum reflectors..