Ok. My 160 Watt self ballastered mercury vapor bulb is getting a little too hot for the weather here as summer approaches. Besides, its about a month or so away from when I had planned to replace it anyway, so I think I'm gonna head over to the store to buy bulbs.

I was thinking of either a 100 watt MVB, or TWO 60 watt MVBs. I would think that the two 60 watts would be better, as a 60 watt drop would be a little drastic as the temps are only a little above what they should be. However, I am hearing contradictory info on MVB UVB output.

Firstly, I am told that the UVB output of an MVB is INDEPENENT of the wattage. i.e., the same UVB output from a 60 watt, a 100 watt and 160 watt, just different electricity consumption and heat (correct me if I'm wrong).

Secondly, I was told by a knowledgeable friend that two 60 watt MVBs would be too much, possibly leading to UVB over exposure. Online care sheets say the same thing. HOWEVER, they are always also (sometimes on the same page) raving about how great direct sunlight is, and how 30 mins of sunlight is better than 12 hours of any bulb commercially available. They are not just referring to florescents either.

So, given that iguanas naturally bask in real sunlight, which supposedly gives off way more UVB than any bulb, how can two MVBs be too much?

Hello,

This is a difficult topic because each MV light emits different levels of UV. If you took 3 MV lights, by different manufacturers, each would have a different reading for UV output.

If I were to voice my opinion on this, I would say that 1 or 2 lights WOULDN'T make a difference. I could be wrong, but this is what I see happening. Lets say you get 2 60 watt MV lights, each emitts 80 uW/cm2 at 24". I don't believe that equals 160 uW/cm2 at 24". I think that is still 80 uW/cm2 at 24", only the ig has a larger basking spot.

Regardless as to how you go with the lighting, there should be a location in the enclosure where the ig can escape from any UV if he chooses. I am interested to hear what others have to say about this.

__________________

hmm...this makes me want to count all the bulbs in the tanning beds that can burn me in 15 minutes...

Sure. I have rep-pro self ballastered spot bulbs and will get those again. I know they were tested by some guys but I never got the results from anyone.
Only that they were quite good but no figures.

If I were to use these bulbs, and have a 4.25 foot platform, how far apart would the lights be to give the same uW/cm2? I would agree with rich that it would have the same UVB at that distance if there is no overlap between the areas of shine, but given that even these SPOT lamps do not only radiate at 90 degree angles but have some spread, how should I position them to take advantage of the bulbs, yet not have much overlap?

Also, since the fringes of the light circle would usually have less intensity of UVB than directly under the face of the bulb, does that make it ok to have a little overlap? Say, if I place it 18 inches off platform, and one one foot into the platform, the other 3 feet into it?

Will two 60 watts likely produce a similar amount of heat as a 120 watt?

Also, when MVBs are put at a slight angle, to give a bigger basking area, does that reduce the amount of UVB? Consider also it is through a mesh, which is bad, but necessary, but the mesh parrallel vs. at an angle.

I was going to go out get a 100 watt today but now I hear rich I am not sure which is better. My ig is 41 inches snout to tail length so I presume it's main part of the body can still fit under a single lamp.

Well when you put two fluorescents in tandem they will give almost if not actually double of a reading. The distance mercury vapor would need to be to get a uniform reading along the basking platform would require a meter. A meter would also be needed to make sure the overlap isn't too high of a reading. Even bulbs by the same manufacture can vary significantly especially if the company has not gotten the technology down. So it would be hard to guessimate what kind of reading you would get.

I got a chance to visit with Bob when he came up here to Ohio for a conference on UVB. My enclosures are 8' in legnth and I have been conteplating making changes on everyone's UVB setup. I talked to Bob about a second basking spot with maybe less UVB than the main one. He said yes to the second basking spot but said no to having any UVB there. He said that the second one should be the same temperature and brightness (regular light bulb) but have no UVB. That way they can still warm up even if they don't need UVB. They will bask in the one with UVB based on their particular needs for UVB. In other words they have a UVB basking spot, non-UVB warming spot, then areas where they can cool down and get away from the UVB both. At least this is what I recall. So I'm incorporating this non-UVB basking spot in both the new and old enclosure.

I think it would be best to go with either the 60 or 100 watt at the appropiate distance and if it is not warm enough increase the supplemental heat (or add supplemental heat). It would need to be mounted at an angle so it is directed to the basking spot.

__________________
Jan. 25, 1963 - Sept. 10, 2006 (R.I.P)

I agree with you marie so I will get a single 100 watt. However, everything I have read about MVBs suggest that they should be mounted directly over head or at a slight angle at most, so that the glare does not hurt their eyes. I think I will try to mount at directly above first and compromise the area of UVB to try it out first. I don't know if I should just get rid of the really old floresecnt (6 months) that I have there still because I think it still has a little bang to it for a couple more months, or would it actually just block part of the UVB from the new bulb. It isn't blocking a lot, about 1/4 of the way from edge of enclosure over the platform, on the corner edge. HAs a reflector to get the light to where I want it.

Sorry to be so confusing. I meant to have the UVB bulb directly overhead. It is the heat that needs to be angled so it hits where the UVB will be hitting.

__________________
Jan. 25, 1963 - Sept. 10, 2006 (R.I.P)