Or just move the bulb further away, or closer to, the cage. If the temps measure 150 with a 60W bulb, move the bulb further away until the temps are acceptable... If it's too cold, just move the bulb closer.
That's why I think it's important to have a flexible lighting configuration above your cage (I'm not a big fan of those combo light fixtures that the reptile-brand companies sell).
Of course, there are always constraints when positioning the bulb in relation to the cage. If the basking spot is not warm enough, and you have to bring the bulb right on top of the cage to get it warm, you risk burning your cham if it climbs on the top screen of the cage. In that case, get a stronger bulb and put it further away.
Likewise, if you don't have enough space in the room to move the bulb far enough away, get a lower powered bulb.
But whatever you do, don't buy those expensive reptile-brand basking bulbs that they sell online and in pet stores. Rather just get much cheaper regular incandescent spot globes from your local home/hardware store, and use the money you saved to buy a decent digital thermometer with an outdoor temperature probe.
Then, like Chad said, measure the temps... That's the only way to get your basking lights set up correctly (and you'll probably need to modify that setup throughout the year as the seasons change and the ambient temperatures fluctuate... once again, the thermometer is your friend).