The aperture is the diameter of the light collecting objective lens or primary mirror of the telescope. It is the main factor that determines the capabilities and limitations of any telescope. Viewing of many celestial objects requires transporting the instrument away from light polluted urban locations to rural or wilderness sites. The ease of transportation and set-up of the equipment will contribute to your actual use of the equipment. Equatorial mountings use tilted axes, one of which is aligned with the earth's axis of rotation, making following the motions of the sky simple.
Equatorial telescopes require some knowledge of the sky on the part of the user.
These are intuitively easy to use, but do not move the same way as the sky. Computer controlled versions are exceptions as they allow a telescope on either type of mount to acquire and track objects, even when used by the novice. These come in achromatic or the much more expensive apochromatic versions. Refractors are available on equatorial as well as altazimuth mountings. They are available on equatorial mounts and altazimuth mounts.