Slow errors in tracking: the periodic wobble of a worm gear, a small polar alignment error, and drift. It cannot correct flexure between the guide scope and the main tube, and it will faithfully make that worse.
Guiding is a feedback loop, and like any feedback loop it corrects what it measures — including things that were never the mount’s fault.
What it measures
The position of one star, repeatedly, through a second small telescope or an off-axis pickoff. When that star moves, the software sends a correction to the mount.
What it fixes well
Periodic error, the repeating wobble a worm gear introduces once per revolution. Residual polar alignment error, which shows as slow drift. And general mechanical imperfection that accumulates over minutes.
What it cannot fix
Flexure. If the guide scope shifts relative to the main tube during the exposure, the software sees a movement that the main sensor did not experience and corrects for it — smearing the image it was meant to protect. Rigid mounting matters more here than optical quality.
What it cannot fix either
Seeing. Atmospheric movement is faster than the loop and essentially random, and a loop tuned to chase it will make the tracking noisier rather than steadier.
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 sensor: a pixel size means nothing without the focal length it sits behind. The same camera is well matched to one telescope and wasteful on another, and a frame rate quoted for the full sensor is not the rate achieved over the small region a planet occupies. This page reports the maker’s figures as published and computes no sampling from them.
The questions that keep arriving
Do I need guiding for short exposures?
Usually not. A well-aligned mount holds round stars for a while unguided, and the length depends on the mount, the focal length and how good the alignment is. Guiding earns its place when exposures reach minutes.
Why does my guiding make things worse?
Most often because it is correcting too aggressively or too often, chasing atmospheric movement rather than real tracking error. The other common cause is flexure, which produces a real signal that has nothing to do with the mount.
Last reviewed 17 September 2026