EQMOD driver supports the N-Point Alignment algorithm.
N-Point basically is a mount stepper coordinate to sky coordinate affine/taki matrix transformation process. The driver internally plots the sky using a minimum of three alignment points (anchor points) as reference points. Pointing accuracy is increased by simply adding more anchor points on different parts of the sky automatically compensating for any mount alignment errors (polar, cone, etc.) yielding more accurate pointing.
Think of the coordinate space of the mount+EQMOD as a rubber sheet with the star database marked on its surface. You place the rubber sheet on top of a star map (your sky) and align the stars on the sheet with the ones on the map. You then lock the sheet with push pins on top of the map. The push pins are now your “anchor points” or “alignment stars” in the real world. To align the markings on the rubber sheet with respect to the catalog points on the map means stretching/ rotating/ scaling specific areas of the sheet and locking them to the star map using the anchor points (push pins).
The affine/taki matrix coordinate transformation routine is actually the one implementing the “stretching/rotating/scaling” functions and needs at least three points as anchor points to define the process.
When you have aligned on more than 3 points, the EQMOD driver dynamically selects 3 anchor points or alignment points from the list of anchor points (N-Point) to apply in the coordinate transformation during a GOTO process.
Accuracy is best within the bounds of the 3 anchor points and degrades dramatically (due the centering errors) as it goes outside the three points. However, if the stars are centered dead-on, even the GOTO's outside the area of the three anchor points should be accurate.
It is best to use points in the area where you most likely to do your GOTO's. If you imagine one big triangle formed by the 3 points, GOTO's will be most accurate within the triangle area.