More magnification equals a better telescope? Beginners often think this, but it is not the determining factor, small or medium levels of magnification are usually more effective. Here you can learn how to calculate magnifications.
A telescope creates a focal point, depending on the curvature of the mirrors or lenses. With the focal length alone, a small level of magnification will be achieved. But in order to be able to look at the image you additionally need and eyepiece. Imagine an eyepiece such as a magnifying lens which enlarges the image at the focal point.