UV question

[Jelly]

When installing a UV tube bulb, should it be 6-8 inches from the top of her head or from her back ?

Also, why does she turn a little darker while basking and turn a lighter, more natural color when I take her out? (basking temp ~100F)
And when taking temps should I be taking the air temp or the temp of the basking surface? (In this case, a repti hammock)

 

[catUK]

Im not so sure about whether its top of head or back. They say 6-8 inches so id probably go for about 6 inches from back as they often lie down whilst basking. They turn darker to absorb more heat. Take the temps directly on basking surface.

 

[jharris08]

6-8 inches from the spot where the dragon is basking the majority of the time is a good distance that will still allow for good UV exposure if you have the correct bulb (reptisun 10.0 is the best)
as far as temps...the spot( log, rock, etc.) where the dragon is basking should be 100-110F , thats the most important thing to get right so that the dragons body temp is warm enough for proper digestion

 

[Jelly]

Thanks

 

[BadCon]

Not to nitpick, but its 6-8" to the top of the dragon...whatever body part that may be. My large male dragon often sits up while basking...when doing so, he's almost 4" tall. This can seriously impact lighting requirement's...and it could be argued that this little misconception with lighting is why MVB's constantly cause eye problems.
The big risk with excessive UV exposure is photo-kerato-conjunctivitis, which is what some call "snow blindness", or "flash-blindness". Too much of the wrong type, or even the good type, becomes a problem...which is why there are distance requirements. Needs to be close enough to get sufficient UVB exposure, but not so close it causes damage. For a Reptisun 10.0, the recommended distance for decent UVB exposure is commonly quoted as 6-10". But the minimum safe distances for a single tube with no reflector is probably around 4". This number goes up if you add another tube in tandem, or use a reflector, and it goes down if there is a screen between the light and the dragon.

I hope that makes sense.