Normally the telescope is polar aligned on the refracted pole to minimize field rotation during tracking. The resulting altitude misalignment introduces pointing errors primarily in Declination as a function of hour angle. These errors can approach 1 arc minute in amplitude. Optical and mechanical non-perpendicularity errors introduce large pointing errors in Right Ascension and may exceed 2 arc minutes in amplitude. The RMS error can be reduced considerably with site and telescope specific pointing model coefficients.
Many professional observatories quote a pointing error in the few arc second range.
However, these values may be the best they have achieved and not necessarily what they achieve on a routine basis. Guiding may be performed with a reticle eyepiece or using some type of electronic detector. In any case, the guider optical system will have a finite field of view. The guider is used to acquire and center the object and then to provide tracking corrections. Small telescopes tend to have a relatively large field of view while large telescopes have a very small field of view so the pointing needs to be better for large telescopes.