Well, they need the bright basking bulb to constrict their pupils so the UV doesn't damage their eyes! Isn't that interesting? I learned that from another person here on the board. So it is better for their eyesight and general eye health to have the bright basking with the UV.
A common household light bulb would suffice as a basking light; just play around with the wattage to determine what gives you the approximate temperature required.