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Mercury vapour, high pressure sodium and metal halide lamps

>Could people kindly recommend a 250W metal halide globe that they have had
>success growing plants with. 
>My current globe is a hydroponics globe (don't know the name) and I am
>looking for a globe with more blue than yellow in the spectrum to balance
>my overall light color. 
>My current setup consists of 2 125W Mercury Vapor Osram globes with large
>amounts of yellow in the spectrum and a half dead 250W metal halide globe.
>Could you please list manufacturers and models. The fixture I have is a
>screw-in single ended lamp.
>Hopefully I can purchase the globes from Australia. The globes that i have
>seen available here are about $100AU each. This is lot of money compared to
>Mercury Vapor globes ($30AU) does this seem right? 

Metal halide puts out white light.

Mercury vapour puts out blueish light.

Hi pressure sodium puts out yellow/orange light.

You cannot get a mercury vapour lamp that puts out yellowish
light. It's most likely a High Pressure Sodium (HPS) light.

In most cases you can't interchange bulbs in a socket; an HPS
bulb will only work with an HPS ballast, dittoo for the other

It sounds like all you want to do is replace your half
dead 250W Metal Halide (MH) bulb.

An MH bulb and an HPS bulb make a lot of sense. The HPS adds
extra red.

You can buy small HPS and Mercury lights - with ballast
and bulb cheaply these days. The local car parts store
("Canadian Tire") sells a 70W HPS "security light" for $70
and a 150W MH for $50. One of each isn't going to cost more
than a decent flurescent setup. The HPS bulbs are also the longest
lasting of any bylb type (incandescent, fluorescent, HID) there

Metal Halide costs more to make (I guess) and is always more
expensive. They make a LOT of HPS and MH for indistrial/street
lighting; the volume is high so the price is low. MH only
differs init's output spectra and is less commonly used
for street lighting, althouh I will say the part of
Toronto we moved from has just upgraded to some twice-as-
many-watts MH lamps; it was like daylight.

Richard J. Sexton                                         richard at aquaria_net
Maitland House, Bannockburn, Ontario, Canada, K0K 1Y0       +1 (613) 473 1719