Under Guiding, you will find mechanical and optical accessories that support the tracking control of an astronomical mount. These are mainly guidescopes and off-axis guiders.
Motorised astronomical mounts compensate for the effect of celestial rotation on the telescope. This way, the telescope remains aligned to a selected object for hours at a time. For this to work, the mount must be positioned precisely. For example, the right ascension axis of an equatorial mount must point as precisely as possible to the celestial pole.
In astrophotography, however, it is not enough to set up the mount as precisely as possible. Depending on the exposure time, the mount’s mechanical inaccuracies may become noticeable. The longer the exposure time, the greater the effect. The mount’s operation must be constantly monitored and corrected. For this purpose, guiding accessories such as a guidescope with guidescope rings or an off-axis guider are required.
If the correction of the mount is done automatically, it is known as autoguiding. For this, you need a camera which continually sends control pulses to the mount over a feedback loop. Suitable cameras can be found here in the category astro-cameras.