The aperture (size) of the telescope's main lens or mirror determines how much light it collects. If you use a high magnification, you are taking that finite amount of light and spreading it over a large image, so the image gets dim. This makes it difficult to see dim objects like comets. But if you use too low a magnification, some of the light is wasted, so for example, if you use 8x magnification on an 8-inch telescope, the view is no better than 8x50 binoculars. Worse actually, because you're only using one eye. So for viewing large diffuse objects, binoculars are ideal. If you can afford large astronomical binoculars (like 16x80) those are ideal, but even a common 8x42 works very well (and don't need a tripod).