One of the most common ways to improve tracking for astrophotography is to use an autoguiding setup. While astrophotography mounts can track extremely well, even the slightest polar alignment error can cause your target to drift over time in your frame. There are two way to solve this: using a guide scope, or using an off-axis guider.
A guide scope (sometimes spelled guidescope) is a small refractor, typically mounted on top of, or beside, the main imaging telescope. A separate camera (known as a guide camera) attaches to the guidescope, and, using software, tracks a star (known as a guide star) and sends corrective commands to the mount to ensure the star does not drift. Autoguiding ensures you have the best possible tracking, giving you pinpoint stars throughout your entire imaging session.
With guide cameras and software, which can detect very slight changes in the motion of guide stars, the focal length of the guide scope should be at least 1/10th the focal length of the imaging telescope. If the focal length of your imaging telescope is 1000mm, then you need a guide scope with a focal length of at least 100mm to give sufficient resolution for effective autoguiding. This rule is not set in stone, but it is extremely helpful to understand what focal length you need.
Various guide scopes are available from top brands including ZWO, QHY, Orion, and Stellarvue. These guide scopes are made to accommodate a variety of guide cameras. Don't see what you're looking for? Let us know so we can help!