nanometers (was: AW: Uranus phaser)

[Haible Juergen]

	>> - Typical CdS LDR's are most sensitive to green light, just like
the
	>> human eye. Using a green LED, especially an ultra-bright green
LED,
	>> will make the current used to drive the LED much lower. 
	>> 
	>??
	>I have seen sensitivity measurement diagrams that show two peaks of
	>equal hights for CdS:  at green 540nm AND orange/red 640nm. 

I think CdS is only one of several materials for LDRs.
There's CdSe (sp?), and probably mixtures of both.
I have no idea what these surplus parts are made of.

	>So these
	>very bright orange/red diodes should be sufficient, they are much
	>brighter then any green led I've ever seen, indeed one should not
	>directly look into the light source, danger of eye damage !

Is this really true? I think that even if there would be danger
when you look at it with an optical device (telescope ...),
it would have to be labelled so. (At least in Germany)
Just wondering.

JH.