Beginner’s Short Guide to Telescopes
- Category: size
- Category: magnification
- Category: types
- Category: mount
Category: size
It is a common misconception that telescopes are distinguished by their magnitude. The truth of the matter is that any telescope with the appropriate eyepiece can reach any level of magnification. Therefore, instead of magnitude, the size of the lance or the mirror is used to categorize telescopes. The larger the size of the lance or the mirror, the more objects you will be able to see and a higher degree of magnitude can be achieved and still provide a nice and sharp image. So, for example, a 10” telescope with magnitude 120x is better than 3” one with the same magnitude.
Generally speaking, based on the size, telescopes are divided into:
- small (4” or less);
- medium (5”-8”);
- large (10” and more).
Although larger telescopes do provide a higher resolution images, they are not necessarily the best choice, since they are less portable and more expensive. You should consider all pros and cons before going for a larger telescope.
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Category: magnification
Yet another common misconception is that the greater the magnitude, the better. As the magnitude rises, the quality of the image decreases, especially in smaller telescopes. Although you can get even the 500x magnification on a smallest telescope (with, as we have explained, very poor image), you are no likely to need magnitude higher than 350x at all. As a matter of fact, you will do perfectly fine with 200x, basically, for any purpose.
By the way, if you are still deciding to go with a smaller telescope, keep in mind that the appropriate magnitude is calculated based on the size of the telescope. For each inch you can have an extra 30-50x magnification in good weather conditions. For example, your 2.4 inch telescope, given the clear sky, can get the magnitude of approximately 120x. To give you an idea that this is not as little as it seems, rest assured that you will see the rings of Saturn or cloud belts on Jupiter.
As you might know, you can change the eyepiece on the telescope, thus changing the magnification. Magnification is calculated by dividing the focal length of the eyepiece into the focal length of the telescope. For instance, the magnification of a telescope of 1000 mm focal length with a lance of 25 mm focal length will equal 40x. This simple formula will help you when you decide to upgrade your telescope.
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Category: types
If you have had any interest in telescopes earlier, you might have heard the words “reflector” and “refractor”, and it is likely you have no idea what they mean, which is very common. So, we will try to keep it as simple as possible not to confuse you any further.
A reflector is called so because it reflects light beams from one mirror to another within the telescope tube and into the eyepiece. These telescopes are less expensive to produce and therefore cost less. Yet, they produce great magnification and images of high quality. For a start, a 4.5” reflector will be just the right thing for you, even with a modest budget.
The problem with the reflectors is that they are not very user friendly: the mirrors inside need adjustments from time to time, and cleaning, since they gather dust. Also, they are not the best option for children, since the eyepiece is located at the top of the tube.
A refractor refracts, or deflects a light beam. It does not use mirrors, but lenses instead. The light travels into the tube through the lance at the top of the tube and into the eyepiece at the bottom. By the way, the symbol of a telescope most people are familiar with – a nice thin slightly widening tube on a mount – is by appearance a typical refractor.
Refractors, as opposed to reflectors, are user friendly – very high quality images, solid design, virtually no maintenance needed, and the eyepiece is located at the bottom of the tube, which makes it accessible for children. Yet, keep in mind that they are the most expensive telescope you might find. The larger the telescope, the higher the price.
Of course, there are fusions of the two types which use both – the mirrors and the lenses, but that’s some more theory for a more advanced read.
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Category: mount
A telescope’s mount is a very important piece. First of all, the tube has to stay firm if you want a sharp image. Secondly, the tube has to move with the object observed so it doesn’t disappear from your site. Without a mount this is impossible to achieve.
There are several types of telescope mounts:
- Alt-Az mount. This is the basic type. The tube is positioned firmly and you can move it up, down, right and left to keep up with your star. This type of mount is inexpensive and hard to break. At the same time, being not so smooth, following the object with this mount is not very easy for beginners, yet manageable.
- Fork mount. This is a type of Alt-Az mount, but with a little motor. It can be used without a tripod. So, you can locate the telescope on a flat surface, like a camera.
- GOTO mount. Another type of the Alt-Az mount, but with a computer which tells you where the object you are looking for is and when you’ve reached it. But after that – you are on your own.
- Motorized GOTO mount. It doesn’t just find the object, it tracks it for you.
- GPS equipped motorized GOTO mount. This is the only type of mounts which locates you, so that you don’t have to input your coordinates manually.
- Equatorial mount. This mount is similar to the Alt-Az mount the only difference being that to follow the object all you need to do is nudge the tube (smooth movement is possible).
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