A simlar discussion took place in another thread.viewtopic.php?f=34&t=107815
That may answer your questions. The bottom line is, we can't tell you a distance for basking temps over the internet...as room conditions vary from house to house. What we can tell you is that he needs to be within 8" or so of the reptisun UVB fixture, and you should use a thermometer, preferably a digital one, to check his basking temps. Shoot for 105 degrees F.