just buy a hooded light fixture with clamp. You can clamp it on the side of the tank for the basking spot. Or if have a screen lid, you can just rest the hood over the screen top (as long as the screen is metal and not vinyl), Use any flood or spot style bulb you can get a a home hardware store or department store. Wattage will vary with your setup but typically 75-125 watt range works for most setups.
You are aiming to provide a basking area with different temperatures locations the dragon can choose from, so a wide sloping basking spot works best...The highest area of the basking spot (big enough for your dragon's entire body to be in the temperature zone) should be around 115F...with lower areas of the basking spot being around 95-110F. This ensures a range of temps for your dragon to choose from.
A temp gun is the best way to measure surface temperatures...if this isn't available then a thermometer with probe that can be laid right on the basking spot (the probe end) but it takes about half hour depending on the thermometer to reach the actual temperature of each spot. (some calibrate as fast as 10 or 15 mins but most take at least 15min).
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PHLdyPayne