Comparison Celestron ExploraScope 114 AZ vs Celestron AstroMaster 114EQ

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 highest resolution magnification that a telescope can provide. In fact, this is the magnification at which the telescope provides maximum detail of the image and allows you to see all the small details that, in principle, it is possible to see in it. When the magnification is reduced below this value, the size of visible details decreases, which impairs their visibility, when magnified, diffraction phenomena become noticeable, due to which the details begin to blur.

The maximum resolving magnification is less than the maximum useful one (see above) — it is somewhere around 1.4 ... 1.5 of the lens diameter in millimetres (different formulas give different values, it is impossible to determine this value unambiguously, since much depends on the subjective sensations of the observer and features of his vision). However, it is worth working with this magnification if you want to consider the maximum amount of detail — for example, irregularities on the surface of the Moon or binary stars. It makes sense to take a larger magnification (within the maximum useful one) only for viewing bright contrasting objects, and also if the observer has vision problems.

The luminosity of a telescope characterizes the total amount of light "captured" by the system and transmitted to the observer's eye. In terms of numbers, aperture is the ratio between the diameter of the lens and the focal length (see above): for example, for a system with an aperture of 100 mm and a focal length of 1000 mm, the aperture will be 100/1000 = 1/10. This indicator is also called "relative aperture".

When choosing according to aperture ratio, it is necessary first of all to take into account for what purposes the telescope is planned to be used. A large relative aperture is very convenient for astrophotography, because allows a large amount of light to pass through and allows you to work with faster shutter speeds. But for visual observations, high aperture is not required — on the contrary, longer-focus (and, accordingly, less aperture) telescopes have a lower level of aberrations and allow the use of more convenient eyepieces for observation. Also note that a large aperture requires the use of large lenses, which accordingly affects the dimensions, weight and price of the telescope.

This item indicates the eyepieces included in the standard scope of delivery of the telescope, or rather, the focal lengths of these eyepieces.

Having these data and knowing the focal length of the telescope (see above), it is possible to determine the magnifications that the device can produce out of the box. For a telescope without Barlow lenses (see below) and other additional elements of a similar purpose, the magnification will be equal to the focal length of the objective divided by the focal length of the eyepiece. For example, a 1000 mm optic equipped with 5 and 10 mm "eyes" will be able to give magnifications of 1000/5=200x and 1000/10=100x.

In the absence of a suitable eyepiece in the kit, it can usually be purchased separately.

The magnification of the Barlow lens supplied with the telescope.

Such a device (usually, it is made removable) is a diverging lens or lens system installed in front of the eyepiece. In fact, the Barlow lens increases the focal length of the telescope, providing a greater degree of magnification (and a smaller angle of view) with the same eyepiece. In this case, the magnification factor with a lens can be calculated by multiplying the “native” magnification with a given eyepiece by the magnification of the lens itself: for example, if a telescope with a 10 mm eyepiece provided a magnification of 100x, then when installing a 3x Barlow lens, this figure will be 100x3=300x. Of course, the same effect can be achieved with an eyepiece with a reduced focal length. However, firstly, such an eyepiece may not always be available for purchase; secondly, one Barlow lens can be used with all eyepieces suitable for the telescope, expanding the arsenal of available magnifications. This possibility is especially convenient in those cases when the observer needs an extensive set of options for the degree of magnification. For example, a set of 4 eyepieces and one Barlow lens provides 8 magnification options, while working with such a set is more convenient than with 8 separate eyepieces.

The presence of a coma corrector in the scope of delivery of the telescope.

Coma is a special type of distortion (aberration) to which the reflectors of the Newtonian system are mainly subject. Coma leads to the fact that at the edges of the image, point sources of light (primarily stars) begin to blur and become similar to comets, whose tails are directed from the centre of the image; and the greater the distance from this centre, the stronger the lubrication. This is not particularly critical for observations, but it can noticeably "ruin the life" of an astrophotographer — especially since it is desirable to use fast telescopes for shooting, and an increase in aperture leads to an increase in coma.

Correctors are used to eliminate this phenomenon. Such devices are lenses of a special design, installed behind the main mirror (when viewed in the direction of the light). At the same time, if the elimination of coma is fundamentally important for you, it is best to purchase a telescope that was originally supplied with a similar lens: it will guarantee that the telescope is compatible with the corrector in principle, and will also save you the hassle of finding and selecting such an accessory.

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).