Old Halogen Chestnut

[OldDave]

Hi WM,

(this is quite fun isn't it )

The info for Halogen is actually for Tungsten Halogen and comes from the Cervantes 'Indoor Bible' which says only 15% of the light O/P is in the PAR range - I'll try to get something from another source. One problem is that the graph gives the impression that red light is higher up the energy scale, when, as you will have found in your research, the blue end of the spectrum is the high energy end as the nm figures are wavelength not a measure of energy, using degrees Kelvin is probably more intuitive. This is important as (unless there's external input) the photons can only move down the spectrum from blue to red, or in this case from red to IR.

You are quite right about the photosynthetic peak at 680nm but this is mostly an internal reaction where the pigments funnel higher frequency energy down to a common reactive centre. I can't find a graph that I can put in the post but according to my text there are 5 main pigments that react to light - chlorophyll-a and -b, caroten, phycobilin and phytochrome, these all produce most of their energy in the range 425-550nm where the halogen produces almost nothing. Unless you're using a spotlight then 70-80% of the light the plants get will be reflected, and so have lost energy....

Still, all this is just theoretical b****x and I expect your plants will thrive I await the pics with great interest

All the best

David

[wintermute]

Cheers David

My knowledge breaks down at the Pysics to Biology interface so i can see what you mean. Overall i think i'm now convinced and i'll get myself a MH, HPS set up to fill my extra space. If i do build a wee halogen set up you'll be the first to see the pic's

WM

[Mono]

Hurray!!!!

Good choice.....

Halogen FAILS....

Mono....x

[oldtimer1]

See I never had to say a word .