Sources of error in this method include the readability of the bubble level, compass, and azimuth scale plus the accuracy of transferring readings to the mount position, so mounts which include these as built-in features are desirable.

When using a compass, be sure to compensate for the magnetic deviation from true north as shown below and keep away from magnetic materials in the mount which may affect compass readings. Magnetic deviation information is shown on USGS topographic maps.