Heat Lamps At Night

Question
I've read that you aren't an expert on Boas. But I'll ask anyway b/c I'm hoping the answer will be general.

I just got a Red Tail Boa yesterday. And I got worried it would get cold at night so I got a heating pad. That's kept the bottom of the tank warm. I'm finding he likes to be on the cooler end. The tank isn't hot it's currently at 85 on the warm end and 75-80 on the cool end.

My question is, when it comes to heating lights, the infrared ones, what's the wattage need at night? I'm starting out with a 50 watt tonight. But is there a general light that's used all around by everyone?  

Answer
You can't really tell by the wattage alone, as it's also a factor of how far away the bulb is from the substrate in the tank. You really need to use a thermometer to make sure the temp is right, or even better a thermostat to control the temp automatically.