Re: Metal Halide/Halogen bulbs

> From: JOlson8590 at aol_com
> Could some of you take a look inside those parabolic reflectors and see what
> kind of bulbs are actually installed?

Yup, real Metal Halide. I have two of them on my two large aquariums.
250watt 5500K. The light is slightly bluish due to the higher spectral
components but this is good for producing red coloration of the leaves.
The color rendition of plants and fish is quite good. For photography
they give pretty good results; much better than conventional tungsten
incandescents. Not sure how they stack up against fluorescents since
these are highly dependent upon the phosphor types employed. For
photography, it's hard to beat sunlight. I'd be interested to hear
other comments on lighting for photography of plants/fish.

When the light switches on, there is a noticeable delay as the light
intensity gradually builds up (the sunrise effect). When it switches off
the light intensity drops to nil very quickly although you can still
see the cathode filament glowing for several seconds. (the sunset effect)

I believe that this type of lighting is now used almost exclusively
in green houses where it is used to supplement lower levels of sunlight
in winter months. They don't use the pendant fixtures however. The
deep parabolic reflectors are used for applications such as stadium
lighting or for illuminating work places at nighttime (like highway or
bridge repairs) where high intensity MH lighting is also useful.

My recommendation is to paint the exterior of your MH fixture with
flat black spray paint and the interior with white enamel. I think
the white enamel will have better reflectivity than the bare
aluminum. Flat black on the outside improves the appearance a
lot and helps keep the fixture cool (flat black radiates heat well).
My fixtures are cool enough that it's no problem to touch them
with your hand. There should be vents at the top to allow
hot air to convect out. If there aren't, drill them before the
ceramic receptable is installed to prevent damage to the receptable
by your drill bit.

It would also be a good plant to situate a shelf on the wall
behind your aquarium so that you can put house plants there to
take advantage of any spare light. Extra frequent watering
is required!

Steve Pushak            spush at hcsd_hac.com        Vancouver BC Canada