"Steve Harris" wrote in message
...
In article ,
(Franz Heymann) wrote:

My problem is essentially to find out quantitatively how many
lamps,
of what power, at what distance from the plants, to use.

Last winter, I couldn't find definitive information either. In the
end I
used a single 21W "energy saver" bulb no more than 9" away from some
seedlings and got reasonable results.

That's a starting point any way. I presume that would do for one
small seedtray.
Just my luck: the biggest energy saver I could find today was 16
watts. {:-((

The other possibility seems to be one of the very high power halide
lamps. I have an unchecked idea that one needs around 1000 lumens per
sq. metre. One of those high powered halogen bulbs of 200 watts
suspended at 50 cm above the table should be able to serve an area of
roughly
50 x 50 cm.
I'll try to look if its spectrum is reasonable.

Franz

Franz