In order to be able to choose a telescope for the beginner or amateur you must first understand what it is you are looking at and looking for. There are some basic items about telescopes that must be understood. Never to worry, it is not as complicated as it sounds.
Aperature is probably the most important specification for any telescope. The term aperature refers to the diameter of the telescopes main optical element. The optical element can be either a lens or mirror. The aperature of a telescope relates to both its light gathering power, and its maximum resolving power. there are other things to learn as you go through this article but always remember the larger the aperature the more a person can see.
The nest thing to remember when choosing a scope is that power is not as important as aperature. the maximum useful magnification of any telescope is about 50 times the aperature in inches. This works out to being about 100x or 120x with the smaller scopes. This is enough power to see the rings of Saturn and even bands of clouds on Jupiter.
When referring to aperature though you should remember that bigger is not always better. Keep in mind that the ability to store and use the telescope is a must. It does no good to have a scope if you can not get it to the place you choose to observe from. It is also no use having if you are unable to set it up yourself. So keep in mind what and where the scope is going to be used for before you buy the biggest you can afford.
Another limitation on larger telescopes is a condition caused by the earth’s atmosphere. The atmosphere limits how much we can see. Planets, stars, and other heavenly bodies tend to wiggle or shimmer as the light passes through our atmosphere. Astronomer’s refer to this condition as seeing and becomes more noticeable with larger aperature sizes. When high power is applied to the scope to view the moon for instance, also magnifies the distortion of light in the atmosphere.
There are really three designs of telescopes to be considered. These are the refractor, reflector, and compound scope. The refractor is what most non astronomical people vision when they think of a telescope. It is simply a long cylindrical tube with a lens mounted at one end and the eyepiece at the other. They are often chosen by enthusiasts with an interest in the planets and the moon. This being because of the sharper image. It is also useful for beginners because it requires less maintenance than a reflector or compound scope. However, for dollar value they are the most expensive per inch of aperature.
The reflector scope uses a mirror to gather and focus the light rather than a lens. the most common places a concave primary mirror at the bottom end of the scopes tube. A small secondary mirror at the other end directs the light out the side to the eyepiece. A reflector of this type offers the largest aperature for the price and if well made can also provide sharper images than the refractor.
The most modern scope is the compound scope which uses a combination of mirrors and lenses to gather and focus the light. The biggest advantage of this type of scope is that it is compact. the mirrors and lenses actually “fold” the light inside the tube making a smaller tube practical. One of the major drawbacks of the compound scope for the beginner would be maintenance. As with all scopes that have mirrors, some time must be spent aligning the mirrors. However, if you want large aperature and portability the cost is still less than a refractor of the same aperature size.
It all boils down to which is the right telescope? there are three pieces of advice:
1. Choose a telescope that you will use. Getting one that stays in the garage is of no use,
2. All else being equal, a larger diameter (aperature) will reveal more of the night sky,
3. Buy from a company that is knowledgeable and will support you after the purchase.