To choose the best telescope, you should consider your particular viewing needs and the different technical aspects of a telescope, including its aperture, focal length, potential magnification, and mounting. In many ways, the most important quantitative measurement for a telescope is its aperture size, in which bigger is almost universally better. You should use the aperture size to determine the maximum magnification and consider the focal length of the telescope to understand what type of eyepiece you need to achieve the magnification you want. The best telescope for you is also likely to be one you can actually use, so you should consider the size of the telescope and what type of stand would work best.
Depending on your individual needs and preferences, the best telescope for you can vary quite a bit. One of the first things you should look for is the aperture size. This indicates the size of the mirror or lens within the telescope and basically indicates that telescope’s ability to gather light. Sometimes referred to as “light buckets,” the effectiveness of a telescope largely depends on how much light it can gather, especially if you want to view objects in deep space.
The best telescope for you should have as large an aperture size as possible, while still being small enough for you to effectively use. Many telescopes are advertised with a particular magnification quantity, but you should typically ignore any advertised amount and instead use the aperture size to determine the maximum magnification for a telescope. Most telescopes can only clearly magnify up to an amount equal to the size of the aperture in inches multiplied by 50, or double the size in millimeters. Maximum magnification is important if you want to observe small, local objects like the moon or planets in the solar system, but is much less important than aperture size for viewing distant objects such as other galaxies.
You should also understand the focal length of any telescope you are interested in, as this has an impact on the magnification. The actual magnification you achieve is based on the focal length of the telescope itself and the focal length of any eyepiece you use. To determine actual magnification, you can simply divide the focal length of a telescope by the focal length of an attached eyepiece. You can use this information to help you choose the best telescope for your needs.
Any telescope you choose should be of a reasonable size so you can actually use it and should have a stable mounting system. Very large telescopes can allow you to see distant objects, but you might not use them very often due to their size. Smaller telescopes are much more useful if you actually use them, so you should consider size as you evaluate the best telescope for your needs. The mounting system you use, such as a tripod, is just as important as the aperture size or any other aspect of the telescope, as this makes the telescope stable. You should look for a telescope with a sturdy mount or stand, though keep in mind that you may end up spending nearly as much money on the stand as you do on the telescope itself.