getting some young turtles this weekend, have a few questions regarding lighting/heating.

now i have a basking light and a UV light that i am going to use for the little guys. But i still have a few questions about that. in a lot of the publications i read they say a day time heating/basking lights needs to be provided, but a night time heat light isn't necessary as long as the ambient temp doesn't drop below 70 degrees. How true is that? and what is the best option?

question two, they're basking light will be about 6 to 7inches above they're basking area. what wattage/type bulb should i use to provide sufficient day time heat without over heating? Thanks in advance for all your help guys.

dave