That's because a telescope with a larger diameter can gather much more light, give a brighter image, and be useful at a higher magnification. For ordinary daytime terrestrial viewing, where lots of light is available, you really don't need a lot of aperture. 60 mm to 90 mm telescopes are capable of providing plenty of detail at the powers usually used. In general, however, you should buy the largest aperture scope which fits your portability and budget requirements. Portability Ordinary telescopes range in weight from only a few pounds to several hundred pounds, and overall bulk varies tremendously.
Some types are quite rugged, while others can require realignment after a little rough handling.
On the other hand, there is no reason to pay for portability if you don't need it. Compare carefully, considering your individual needs. Photography Most telescopes can be used for high-powered terrestrial or astronomical photography, as long as you have a removable lens type 35 mm SLR camera. The compound telescope is the most useful for general use, as it's ideal as a telephoto lens. Astrophotography is an interesting and rewarding hobby.