It tilts one axis of the mount until it points at the celestial pole, so that a single motor turning at the rate of the sky cancels the rotation of the Earth. Without it, an equatorial mount tracks nothing and is simply a worse alt-azimuth head.
Every complaint that an equatorial mount does not track comes back to this, and it is a single idea rather than a skill.
The idea
The sky appears to turn because the Earth does, about an axis that points at the celestial pole. Tilt one axis of a mount to match that axis, and a single motor turning once a day in the opposite direction holds an object still.
Why Polaris is not the pole
Polaris sits near the north celestial pole, not on it, and circles the pole once a day. Pointing straight at it leaves an error large enough to ruin a long exposure, which is what the marked circle on a polar scope reticle exists to correct: it says where on that circle Polaris should be at this date and time.
What good enough means
It depends entirely on what comes next. Visual observing tolerates a rough alignment. A tracked exposure of a minute wants better. Guided imaging wants better still, and at that point software routines that measure the error directly become worth the time they take.
An unaligned equatorial is a worse alt-azimuth
The mount still moves both axes, but neither of them matches the sky, so an object drifts out of the field and the field also rotates. That is the situation an unaligned equatorial head is in, and it is worse than an alt-azimuth mount because it is harder to push.
If this page and the manufacturer’s own documentation disagree, follow the documentation. Every aperture, focal length, payload rating, field, eye relief, transmission figure and thread size on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And for any payload figure: makers quote it for observing, and photography asks for a considerably wider margin. A tracking error invisible at the eyepiece is a smeared star on a sensor, and the rating usually excludes the counterweights. This page reports the maker’s figure with the use it was quoted for, and derives no photographic capacity from it.
The questions that keep arriving
How accurate does it need to be?
For visual use, roughly aiming at Polaris is enough to keep an object in the field for a long time. For exposures of minutes, the alignment has to be good enough that the drift is smaller than a star image, which is where a polar scope or a phone routine earns its place.
What about the southern hemisphere?
There is no convenient bright star near the south celestial pole, so the routines differ and many reticles carry a separate pattern for it. Mounts sold in both hemispheres usually support both.
Last reviewed 17 September 2026