pietkuip:
A voltage divider with 10k resistances would probably be better.When the analog input is reading a value, a sampling capacitance must be charged. That may inflence your readings.
The fixed resistor value should be the same as the thermistor for maximum A/D resolution.
If the value is >10k, it is wise to add a 100n cap from analogue-in to ground.
Then the A/D sees a "solid" voltage during sampling.
Digital temp sensors like the DS18B20 are easier to use than thermistors.
Leo..