UV Lights--another view, continued

Leptraps at aol.com Leptraps at aol.com
Mon Apr 1 21:30:50 EST 2002

Mike Soukup wrote:

>And, although it "doesn't seem right", when I was 
>collecting in AZ  (and Costa Rica) 2 years ago, I had 
>1 clear 175 MV bioquip setup and 1 of their frosted 
>self-ballasted MV bulbs (not the new clear ones they 
>have now).  The frosted bulb outdrew the clear bulb 
>at "about" the rate of 1.5 to 1. 
>My personal "guess" is that the 175w clear bulb 
>actually "drew more into the area"...but not to my 
>sheet.  Whereas the frosted bulb brought them all the 
>way in. (I "kinda" tested this by only setting up the 
>clear bulbs in C.R.  By 2AM, I could see - using my 
>flashlight - some larger Saturnids and Sphingiids "out 
>of my reach" (there were also many on my sheet).  So, 
>I then set up my frosted bulb.   By 4AM, several of 
>the Sats had moved onto my sheet. 
>So, I now try to use both - one frosted - one not!!! 
>>Kenelm Philip wrote: 
>>There appears to be a latitudinal/elevational effect 
>>in the relative utility of MV vs. low-power 
>>fluorescent UV bulbs. I had commented to Cliff Ferris 
>>about my observations here (Interior Alaska) that MV 
>>bulbs didn't seem to be that much more effective than
>>8W fluorescent bulbs--and he replied that he had seen 
>>the same thing happen at higher elevations in the 
>>Rockies. In Arizona, on the other hand, he said there 
>>is a marked difference in the favor of the MV bulb, 
>>especially with regard to Saturnids and Sphingids 
>>(which are not exactly abundant up here--4 Sphingids 
>>and no Saturniids.
>> Ken Philip

I design light traps and as a result, I read a good bit of material on the 
subject of UV light. I read an article a number of years ago on arc tube 
technology (which includes Mercury Vapor) and the effect of reflective light 
from the moon on artificial light. Simply put, the farther north the sun 
travels in the summer sky, the smaller the angle of deflection, the more UV  
light directly from sun is exposed to the surface of the earth when the sun 
is below the horizon. This angle of deflection has a huge impact on 
artificial blue UV light bands. The same is true of a full moon which 
reflects UV sun light at lower latitudes. Once the blue UV light bands or 
wave patterns of artificial UV light are interrupted or distorted, their 
effectiveness is diminished and as a result its effect on insects is reduced. 
This would help explain Ken Philip’s success with fluorescent and the 
lack of the same with MV.

I have used both clear and frosted MV bulbs, the smaller self ballasting 
bulbs are coated with a material that enhances the blue UV bands. The reach 
or distance the blue UV bands are effective is greatly reduced. I as stated 
in a previous post:

>>Fluorescent UV bulbs produce UV light with a much 
>>shorter reach. Increasing the wattage from 15 to 40 
>>will only increase the reach by 15%. The most 
>>effective bulbs are straight tubes. When placed in 
>>front of a white sheet or mounted in the center of 
>>the vanes on a light trap, these fluorescent tubes 
>>will emit unobstructed UV light 360 degrees. The 
>>reduced reach is the result of the length of the 
>>tube. The larger the diameter of the tube, the 
>>shorter the reach. There are actually three types of 
>>fluorescent bulbs/tubes available. A Black Light 350 
>>(A white colored bulb)is a tube with a white coating 
>>on the inside walls of the tube. Unlike the coating 
>>on the inside of MV bulbs, the coating in a 
>>fluorescent tube enhances the blue band with minimal 
>>distortion. The Black Light Dark (A dark purple 
>>colored bulb) emits a very effective blue band, 
>>however, the coating on the inside of the tube also 
>>reduces the reach. I use both type of bulbs on my 
>>rigs. It is my opinion that the dark tube has the 
>>ability to hold insects at the sheet than a regular 
>>white UV bulb. 
I use both MV bulbs and both types of 40 watt fluorescent tubes (Black Light 
and Black Light Dark) on my rig. I have found that the MV draws them in and 
the fluorescent’s hold them. I would assume that this may be true for 
coated MV bulbs as well.


Leroy C. Koehn
Georgetown, KY

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