go to walmart and spend $8 on an acurite digital thermometer/hygrometer
i try to keep my enclosures from dropping below 60%, 55% makes me nervous and 50% is a definite no-no IMO. the minimum % typically ranges from 50-55%, but IMO 55% is not a "good humidity level."
for shedding i keep the humidity above 70% throughout the entire cycle until the snake sheds.