Reptile & Amphibian Forums

does anyone have their lights possitioned at an angle (say 45 degrees) and does it have the same effect as if it was directly down? i heard a couple times that its best to set the light so it goes directly down. but i want your guys's opinion. thnx

From a point source of light, light intensity is simply calculated by multiplying its power by the reciprocol of the distance squared:
lightpower/distance^2
or
lightpower/pow(distance,2)
depending on what represntation you prefer. You're already looking at a beam that has a hotspot and falls off towards its edge, so you have lineal falloff (calculable and regular) and axial falloff (dependant upon the fixture).

So... a spot-type of light aimed at a perpendicular surface will have its highest intensity at its center, but a light aimed towards a similar surface at an angle will have a more elliptical shaped hot-zone with the hottest area biased towards the light. You should have a larger not-so-hot area so it would be a useful way to disburse an overly powerful light in the same amount of space.
The angle only changes the distribution/focus of energy- the output is still the same. So increase/sustainence of average cage tmperatures will be the same, although the location and distribution of the gradient will be altered.

You can throw all kinds of trig in there to figure out relative values or make a map, but that's excessive for something you can just move and measure- particularly where fixed target values are not necessary. For a normal example of what happens, this is the effect responsible for the change of temperatures over the seasons during the year. Slight angles can have a fairly impressive effect. If you're playing with a lineal light source like a fluo tube, falloff is a little bit different, but this is close enough for government work.
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2.4.0 uromastyx geyri (Saharan/Nigerian)
0.0.4 uromastyx hardwickii (Indian)
2.3.0 uromastyx macfadyeni (Somalian)
1.3.0 uromastyx ocellata (Sudanese)
"Yes, it's a problem. No, I don't want to talk about it."

MAybe the position thing was pertaining to mercury vapor bulbs which have to be pointed straight down to prevent premature burn out.
-Alice

I'm having a difficult time locating any information pertaining to vertical installation of mercury vapor bulbs. Where are you repeating this from and why would a standard light care? None of my lights indicate this in their packaging at all.
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2.4.0 uromastyx geyri (Saharan/Nigerian)
0.0.4 uromastyx hardwickii (Indian)
2.3.0 uromastyx macfadyeni (Somalian)
1.3.0 uromastyx ocellata (Sudanese)
"Yes, it's a problem. No, I don't want to talk about it."

Word on the UVB meter owners group is that this is just an excuse provided by some of the companies when people call in to make a claim on the warranty when bulbs burn out early. It's not true - there's no difference in decay or burnout rate of MV bulbs whether placed vertically or at an angle. This is based on findings from personal testing by Robert MacCargar (the king of MV bulbs, IMO) of hundreds of bulbs of different brands. There was a theory posed by someone in the group that the lamp guts (technical term ) might sag when the lights are on (and hot) and burn out when it sagged far enough to touch the sides of the glass envelope, but I don't think that was ever verified in any way. If you want more info, you can join the UVB meter owners group on yahoo and dig in the old messages.
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Torey
Eugene, Oregon, USA
1.1 Uromastyx geyri (Joe and Arthur)
3.0 Uromastyx dispar maliensis (Tank, Turtle, and Spike)
1.0 Uromastyx ornata (Scuttlebutt)
2.1 Anolis carolinensis (Bowser, Sprocket, and Leeloo)
0.1 African dwarf frog (Sheila)
1.0 Betta splendens (Mr. Miagi)
1.1 Felis domesticus (Roscolux and Jenny)