redearslider.com

This is probably a repeat lighting question, but I can't find it or the answer.
How far from the basking area should a tube Repti-Glo 8.0 be? And how about a Reptisun 10.0 compact?
And one more: I read about adding a reflector to the UVB tube light that will almost double it's UVB output. How much UVB is too much, and how do you know if the turtle is even getting enough?
I recently renewed my UVB tube to a Repti-Glo 8.0, it's a 24", and only about 1/3 of it is over the basking area because that's all that will fit. I think I'll can it and get a 10.0 compact with a clip on lamp that I can place next to the UVA lamp so all the rays are directed onto the basking area. I think I may be getting a little paranoid, lol.
Thanks in advance for help/suggestions

The reptiglo and reptisun bulbs should be 10-12 inches away from the basking area. Short of the long term ramifications from not enough UVB, I'm not really sure how to tell if there is enough. There are meters that test how much UVB is being given off, but I don't know if it tests the bulb, or tests the basking area. As far as I know, there is no such thing as too much UVB.

Look here:
http://www.uvguide.co.uk/index.htm
Lots of info on UV lighting.....

Yes, that was a lot of info! I found a chart on the Reptisun 10.0 compacts that show the output drops from 33% down to 18% after just 150 hours of burning time. Then between 150 and 750 hours, they drop from 18% to 16%. At 10-12 hours a day, that means those bulbs lose quite a bit of their efficiency within just 2 weeks, holding a steady 18% for about another 2 months. I'm not sure if it means % or not, but the charts says "UVB output" on the left.
Here's the link to what I read on that site:
http://www.uvguide.co.uk/compactlamps.htm
It seems a high price to pay for those bulbs if they don't measure up to the percentage they claim to. I'm going to research the tubes tomorrow, I'll post my findings. If any of you read that info and get a different view on it, let me know.
Thanks Missi and Grey for your replies and info!

So I researched the UVB flourescent tubes and this is what I found:
I use a Repti-Glo 8.0 24" which starts out at a 55% and drops down to 35% after 105 hours of burning at a distance of 6" from basking area (about 8-10 days at 10-12 hours a day), and gradually declines within a year. Fitted with a reflector, it starts out at 120% and over a period of 1 year, it drops down gradually to about 75%, at 6" away and 10-12 hours burn time per day. Seems a lot less drastic of a decline than the compacts.
Another interesting fact, because I truly didn't understand the UV percentages claimed on the bulbs packaging, this site explains it. A bulb that says 30%UVA and 5-8%UVB ouput has a visible light output of about 62-65%. That means that 5-8% of the bulb's output is emitted as UVB, 30% emitted as UVA and the rest is visible light. It doesn't tell how powerful the tube is, only the proportions of the bulb's output. So, the higher percentage of UVB the package says, the higher the proportion of UVB, not the actual UVB rays percentage the animal receives.
If the tube bulb is fitted with a reflector (aluminum pre-made or foil home-made), the amount of UVB is almost doubled. Positioning of the light over the basking area is important with the reflector fitted bulb so as not to have the animal be exposed to excessive glare. For turts, most of us postion our lights above the bask area, which keeps the glare in the tank to a minimum.
I apologize if this is too long of a post. I was excited to share the info! All of this is available on the link Grey Goose provided (again thank you!), if anyone wants to read up on it themselves. Also, please correct me if you feel my findings to be inaccurate.

There were many complaints about the compacts when they first came out, but I think Zoo-Med made the corrections. I've been using one for about 6 mo. now, I got it when the three babies were dropped on me. No problems, but how would I know? The turts growth rate? Appetite? Color? That's part of the problem that keepers have with UVB. Short of buying a UVB meter for almost 200 large, (and then trying to interpert the readings) how exactly do you know how much (or little) your turts getting?
Anyway, here's another article on all things UV.....
http://atphabitats.com/index.php?option ... view&id=40

Thanks for all that educational information! I enjoy reading up on anything that helps me take care of my pets and family, even if it is all technical, lol.
See, that's the problem I have, trusting the UV bulbs because we're supposed to just have blind faith that the manufacturer's claims are correct. I guess it's that way with most products, but this is really hard to determine unless, like you said, you invest in and know how to use the meter. Missibsu has a place she can take her bulbs to and have the UV output checked. I'm sure there's many places like this all over, I'm still looking for one locally. I would love to be able to take my bulb in once a month to be checked.