What temp to set my t-stat on

[alittleFREE]

What do I set my rheostat to for my undertank heaters? (Ball python)

Use a temp gun (or thermometer if temp gun is not available, but temp gun preferably) to measure the temperature of the the cage floor above the UTH, and adjust the rheostat until that surface is consistently 88-90* or so (hot side) or 78-80* (cool side).