The type of mount the telescope is equipped with.
A mount is a mechanical unit with which the telescope is attached to a tripod or (in some cases) installed directly on the ground. In addition to mounting, this unit is also responsible for pointing the optics at a certain point in the sky. The most popular nowadays are
azimuth devices in different variations -
AZ1,
AZ2,
AZ3, as well as in the form of the so-called
Dobson mount.
Equatorial mechanisms of different models (
EQ1,
EQ2,
EQ3,
EQ4,
EQ5) are noticeably more complex and more expensive, but they provide more possibilities. There are systems that combine both of these types of mounts at once - the so-called azimuth-equatorial ones. And finally, some telescopes are supplied
without a mount at all. Here's a more detailed description of these options:
- Azimuthal. The full name is “alt-azimuth”. Traditionally, it has two axes of rotation of the telescope - one for pointing in altitude, the second in azimuth. Different models of such mounts differ in additional control capabilities:
- AZ1. They d...o not have a precision movement system.
- AZ2. Equipped with a system of precise vertical movement (around the horizontal axis).
- AZ3. Equipped with precision movement systems on both axes.
In any case, the second axis (azimuthal) in such systems is always located vertically, regardless of the geographical location of the telescope; This is the key difference from the equatorial mounts described below. In general, azimuth mechanisms are quite simple and inexpensive in themselves, while being quite convenient and practical, which is why this option is the most popular in our time. In addition, they are ideal for observing ground objects. The key disadvantage of this option is its poor suitability for continuous “accompaniment” of celestial bodies (moving across the sky due to the rotation of the Earth). If in a correctly configured equatorial mechanism you need to rotate the telescope along only one axis, then in the azimuthal mechanism you need to use both axes, and unevenly. The situation can be solved using an auto-tracking system, but this function significantly affects the price of the entire device. And even its presence does not guarantee that the telescope is suitable for astrophotography at long exposures - after all, with such use it is necessary to ensure not only accurate movement along each individual axis, but also correction for image rotation in the frame (which is not provided in every auto-tracking system, and also increases the price more).
- Dobson. A specific variation of the alt-azimuth mounts described above, used almost exclusively in reflectors. It also provides two axes of rotation - horizontal and vertical. The key feature of the Dobsonian mount is that it is not designed for a tripod and is mounted directly on the ground or other flat surface; For this purpose, the design provides a wide, massive base. Such systems are excellent for Newtonian telescopes, in which the eyepiece is located in the front part: thanks to the low position of the tube on the mount, the eyepiece itself is at a fairly convenient height. Also, the advantages of “Dobsons” include simplicity, low cost and at the same time good reliability, making them suitable even for large and heavy telescopes. Among the disadvantages, we should note the poor compatibility with uneven surfaces, especially hard ones, like solid rock (while tripods used with other types of mounts do not have this disadvantage).
- Equatorial. Mounts of this type make it possible to synchronize the movement of the telescope with the movement of celestial bodies across the sky, resulting from the rotation of the Earth. The conventional vertical axis, responsible for rotating the telescope from side to side, in such mechanisms is called the right ascension axis (RA), and the horizontal (for pointing along the conventional vertical) is called the declination axis (Dec.). Before use, the equatorial mount is adjusted so that the right ascension axis is directed to the “celestial pole”, parallel to the axis of rotation of the Earth (“the celestial axis”); the specific inclination relative to the vertical depends on the geographic latitude of the observation site. This format of work significantly complicates both the design of the mount itself and the installation procedure. On the other hand, equatorial systems are ideal for long-term “accompaniment” of astronomical objects: in order to compensate for the movement of a celestial body due to the rotation of the Earth and keep the target in the field of view, it is enough to rotate the telescope around the RA axis to the right (clockwise), and with a clearly defined speed - 15° per hour, regardless of the vertical position of the object. This makes such designs ideal for astrophotography, including deep space objects that require long exposures. In fact, this does not even require a full-fledged auto-tracking system - a relatively simple clock mechanism that rotates the telescope around the right ascension axis is enough. The downside of these advantages, in addition to the mentioned complexity and high cost, is their poor suitability for large, heavy telescopes - as the weight of the instrument increases, the weight of a suitable equatorial system increases even faster.
As for the different models of such mounts, they are marked with an alphanumeric index, from EQ1 to EQ5. In general, the higher the number in the designation, the larger and heavier the structure itself (including the tripod, if supplied), the less suitable it is for moving from place to place, but the better it dampens vibrations and shocks. But the restrictions on the weight of the telescope are not directly related to the equatorial mount model.
— Azimuthally-equatorial. Mechanisms that combine two types of mounts. It looks like this: an azimuthal system is installed on a tripod, and an equatorial system is installed on it, in which the telescope is already mounted. This design allows you to use the capabilities of both types of mounts. Thus, the azimuthal mechanism is quite suitable for observing large celestial bodies in near space (the Moon, planets) and large areas of the sky (such as constellations), and it does not require complex preliminary settings. And for astrophotography or for viewing deep space objects at high magnifications, it is more convenient to use the equatorial system. However, in practice, such versatility is extremely rarely required, despite the fact that the combination of two types of mounts complicates the design, increases its cost and reduces reliability. So this option can be found in single models of telescopes.
- Without a mount. The complete absence of a mounting system in the kit does not allow using the telescope out of the box. However, it can be the best option in some cases. The first is if the customer wants to choose the mount at his own discretion, without relying on the manufacturer's decision, or even assemble it himself (for example, quite a lot of astronomers make their own Dobsonian systems). The second typical case is if the household already has a mount (for example, from an old telescope that has fallen into disrepair), and there is simply no need to overpay for a second one. In any case, when choosing such a model, you should pay special attention to the type of fastening for which the pipe is designed - compatibility with a specific mount directly depends on it.
The type of finder provided in the design of the telescope.
A seeker is a device designed to point the device at a specific celestial object. The need for such a device is due to the fact that telescopes, due to the high magnification, have very small viewing angles, which greatly complicates visual guidance: such a small area of \u200b\u200bthe sky is visible in the eyepiece that it is possible to determine from these data exactly where the telescope is pointed and where it needs to be turning around is almost impossible. Pointing "on the tube" is very inaccurate, especially in the case of mirror models that have a large thickness and relatively short length. The seeker, on the other hand, has a low magnification (or works without magnification at all) and, accordingly, wide viewing angles, thus playing the role of a kind of “sight” for the main optical system of the telescope.
The following types of finders can be used in modern telescopes:
—
Optical. Most often, such finders look like a small monocular directed parallel to the optical axis of the telescope. In the field of view of the monocular, markings are usually applied, showing which point in the visible space corresponds to the field of view of the telescope itself. In most cases, optical finders also provide a certain magnification — usually on the order of 5 – 8x, so when working with such systems, usually, the initial pointing of the telescope "
...on the tube" is still required. The advantages of optics, as compared to LED finders, are the simplicity of design, low cost, and good suitability for observations in the city, suburbs, and other conditions with fairly bright skies. In addition, such devices do not depend on power sources. Against the background of a dark sky, the markings may be poorly visible, but for such cases there is a specific kind of finders — with an illuminated crosshair. However the backlight requires batteries, but even in the absence of them, the markings remain visible — as in a conventional, non-illuminated finder. Devices of this type are indicated by an index traditional for optics of two numbers, the first of which corresponds to the multiplicity, the second to the diameter of the lens — for example, 5x24.
— With point guidance (LED). This type of seekers is similar in principle to collimator sights: an obligatory design element is a viewing window (in the form of a characteristic glass in a frame), onto which a mark is projected from a light source. This mark can look like a dot or another shape — crosshairs, rings with a dot, etc. The device of such a finder is such that the position of the mark in the window depends on the position of the observer's eye, but this mark always points to the point at which the telescope is pointed. LED finders are more convenient than optical ones in the sense that the user does not have to bring the eye close to the eyepiece — the mark is well visible at a distance of 20 – 30 cm, which makes it easier to point in some situations (for example, if the observed object is located close to the zenith). In addition, such devices are great for working with dark skies. They usually do not have magnification, but this cannot be called a clear disadvantage — for a seeker, a wide field of view is often more important than zoom. But from the unambiguous practical shortcomings, it is worth noting the need for a power source (usually batteries) — without them, the system turns into a useless piece of glass. In addition, collimators as a whole are noticeably more expensive than classical optics, and the mark may be lost against the background of an illuminated sky.
Note that there are telescopes that do not have seekers at all — these are models with a small objective diameter, in which the minimum magnification (see above) is small and provides a fairly wide field of view.The total weight of the telescope assembly includes the mount and tripod.
Light weight is convenient primarily for "marching" use and frequent movements from place to place. However, the downside of this is modest performance, high cost, and sometimes both. In addition, a lighter stand smooths out shocks and vibrations worse, which may be important in some situations (for example, if the device is installed near a railway where freight trains often pass).
