This interesting bulb, meant for indoor plant growing operations, combines two different arc discharge tubes in one, to provide a wider spectrum of light than either type would alone. One is a high-pressure sodium arc, the other is a metal halide tube, probably containing scandium as a spectrum-enhancer.
Source: eBay seller garden_supply
Contributor: Theodore Gray
Acquired: 2 April, 2009
Text Updated: 3 April, 2009