sunlight is very beneficial for him.
The best time to bask for him is 10 am to 2 pm.
put the cage half in sunlight and the other half in shadow, so he can escape from the heat if he is overheating.
he'll generally go to cooler area when he had enough.
That's why you need to supervise him.
I always believe that the longer you can put your cham outside for basking, the better..
Just remember to give him an area to escape from the sun if he wants to.