It seems very odd that the OP can only measure to a precision of a few degrees using an alchohol or mercury thermometer. The ones he has used are perhaps not photographic thermometers?

The photographic alchohol thermometers I have used are scaled in half-degrees and can easily be interpolated to a quarter due to the size of the scale. The certification is for 0,25 C and that is more than adequate for most use.

Also, beware electronic thermometers quoting (or confusing) the difference between precision and accuracy. Just because the scale goes up and down in, say, 0,1 C increments does not mean that the unit is telling the truth . . .