Each of us, at least once in our life, was visited by the thought, “I wish I could look at these stars through a telescope!” For a long time, people had a dream of being at least a little closer to the sky, understanding its essence, seeing it closer, and getting to know it. Previously it was not possible until Galileo Galilei in 1609 created the progenitor of the modern telescope – he improved the telescope by making it with a threefold magnification. Centuries passed before telescopes reached the level we have now. But how to choose among such a wide variety exactly that telescope ideal for a particular person?
First of all, you need to answer some questions: who will observe through this telescope- a child or an adult, and whether you will have enough time to study astronomy – in other words, will you be an amateur, occasionally looking into the lens, or you will become a more professional observer. The parameters for choosing a telescope depend on these questions.
What do you need to look for in a telescope? If a telescope is required mainly to observe the starry sky, then it is unnecessary to give a direct image of objects and focus on close ground objects. It allows you to see even fainter objects. Over time, if you seriously engage in this science, you will desire to study various specific things in space, such as distant galaxies, which will lead to the need to purchase a telescope with a large lens diameter. Some parameters need to be considered while choosing a telescope:
• Optical design is the basis of the telescope; they are mirror (reflex), lens (refractory), a mirror-lens.
• Objective diameter – the larger the objective diameter, the greater the telescope’s aperture and resolution. So it becomes possible to see dimmer objects. This parameter dramatically affects the dimensions of the device and its weight.
According to this parameter, telescopes are divided into long-focus and short-focus. • Focal length is a particular distance at which this telescope can focus. A long focal length means a larger magnification but a smaller field of view and aperture ratio. Small focal length – on the contrary – means slight exaggeration with a large area of view.
• A pry bar – a method of attaching a telescope to a tripod.
o Azimuthal – which freely rotates in two planes
o Equatorial – tunes to the pole of the world and allows you to see celestial objects, knowing their hour angle
o Dobson mount – a type of azimuth mount that will enable you to establish larger telescopes.
o Automated – with GPS, it is applied for automatic guidance to celestial objects.
The optical component is one of the most important in choosing a telescope. That is why it is necessary to take into account some of the features of each type of optics:
• Refractor – its objective lens is a lens system that collects and concentrates light. They have a reliable design, sealed tubes, little influence of temperature and humidity on them, and can be applied even for terrestrial viewing. The disadvantages include the fact that they have a large mass compared to reflectors and combined telescopes and the fact that they are not suitable for viewing dim galaxies and nebulas.
• Reflector – the lens of the device consists of the primary and secondary mirrors, the main one – collects light and directs it to the secondary, and then it reflects the rays towards the eyepiece. They have small dimensions, no chromatic distortion, are convenient for photographing astronomical objects, and are adapted for observing faint objects in deep space. The disadvantages include a long time of thermal stabilization, inapplicability for ground-based observations, and the fact that a coma is noticeable at the edges of the field.
• Combined – mirror-lens optical system. They have a wide field of view; they are compact and portable and have minimal impact on picture quality from durable air. Between disadvantages are long focal length, long thermal stabilization time, and problematic obtaining of a large–aperture device.
So you will ask: how to choose the best telescope? We already know the parameters for selecting telescopes, their basic – optical system, and what they are. The main rule when choosing this device is an important fact – the larger the tube diameter is, the more you can see. Magnification is not the main factor because it can be changed with the additional eyepiece. Therefore, the diameter of the aperture is a parameter that you need to rely on. It is always indicated in the name: for instance, Sky-Watcher BK 1149EQ2 has an aperture of 114mm. The pry bar is an equally important part. The more powerful it is, the more stable the telescope is, and the more stable the picture is. Do not forget that almost any telescope can be improved.
Choosing a telescope is a responsible and challenging process. Many factors need to be considered when selecting a device – mount, aperture, focal length, and optical design. But knowing the features of each of the parameters, you can make the right choice!
Still, one rule must be noticed – do not buy a telescope with the expectation of a lifetime because this device is relatively highly specialized and requires handling skills that a beginner may not possess.