UV Lights--another view

Kenelm Philip fnkwp at aurora.alaska.edu
Wed Mar 27 05:30:03 EST 2002

After reading Leroy Koehn's posting on UV light traps, I thought it might
be useful to have another note regarding what might be considered the low
end of UV moth traps. For some time now I have been using very low-wattage
fluorescent UV traps, some of them home built, others old BioQuip models,
all using straight tubes.

My home-made traps use 4W BL bulbs, and have aluminum vanes--the BioQuip
traps use 8W BL bulbs, and have plexiglass vanes (1978 vintage, their
model 2850 trap). I used to run these off AC, but recently I began moth
trapping on field trips in Alaska and the Yukon, and modified the Bio-
quip traps to run off motorcycle batteries (which I am about to set up
to be recharged off my truck's alternator while driving).

For DC->AC convertors, I tore apart some KMart battery-operated fluorescent
lamps with 8W bulbs, and placed the high-frequency (and thus very small)
ballast etc. in a little project box, added battery clips, and replaced
the fluorescent bulb with a BL bulb. These drop right into the BioQuip
traps, and are very cheap. The 8W KMart units run off 12VDC. Walmart
has similar units.

These low-wattage traps seem to work just fine up here. I have a 15W UV
traps that does no better, and the 8W traps will run for 2 or three of
our short summer nights without recharging the battery. And I have watched
Jim Kruse running a MV lamp, and did not see all that many more moths
coming in than my low-wattage traps get at the same spot.

I fail to see any great advantage from using transparent vanes. With metal
vanes much of the lamp is visible from all angles. If Koehn's comment
about a larger-diameter bulb having a shorter reach is correct, then the
metal vanes would be _more_ effective, since they make the bulb look a bit
narrower from some angles.

I do not understand what Koehn is referring to in his remark that:

> The inward facing surfaces emit light that conflicts and is distorted
> from light emitted from the other inward facing surfaces

when using circular or U-shaped fluorescent bulbs. I would agree that a
lot of the light produced is being wasted, compared to a straight bulb
of the same wattage--but _distorted_? The waste comes simply because
the light from such inner surfaces cannot all be seen from outside, since
the bulb itself blocks the light.

							Ken Philip


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