Ignore the chart... They do not account for the screen that the UVI has to go through. The screen reduces the output by about 40%. So we are aiming for an approximate UVI exposure level of 3 at the branch. Then on the screen the max exposure of 6. The info I gave you will give you these levels.
you will have baby screen climbing constantly to get to the UVI levels it needs due to how it is set up now. With your current set up 8 inches to the screen is putting him at a 3 uvi but at the branch being 14 inches away it would be below a 1 UVI level. This puts baby at risk for MBD developing.
While you may be able to see the light this does not mean that the UVI level penetrates that deeply into the enclosure. It is one of those areas of cham keeping we have to be very careful with because of MBD.
