①Horizontal type (theodolite): such as Celestron AZ series telescope
Advantages: cheap, light weight, easy to carry, simple structure, easy to debug. Disadvantages: low adjustment accuracy, poor stability, unable to track celestial bodies, and unable to perform astrophotography.
②Equatorial Ceremony: Ruxingtron EQ series telescope
Advantages: high adjustment accuracy, can track the movement of celestial bodies, and can perform astrophotography. Disadvantages: heavy weight, difficult handling, complex structure, troublesome debugging. Divided into manual and electric, the manual tracking equatorial mount is suitable for specialized astronomical observations, and the electric tracking equatorial mount can be used for specialized astronomical tracking photography and observation research. Beginners can choose a manual equatorial mount after they are familiar with the horizon type; they may find it complicated to adjust for the first time, but it will be much easier to observe the stars after they are familiar with it; amateurs learn astrophotography and often use electric tracking equatorial mounts.
Fourth, the identification of the optical quality of astronomical telescopes
During the day, use a telescope to observe the leaves in the distance. Generally, a 60mm diameter telescope can clearly see the leaf tendons at a distance of 40 meters. If you can't see clearly, the optical quality is poor. When you observe stars at night, if you see stars with obvious colors, or It is the star at the edge of the field of view that is dragging its tail, and its length is twice the size of the star, indicating that the optical quality is very poor and it is not suitable for astronomical observation.
*Choose the 31.7mm (1.25 inch) large eyepiece mount for better optical quality.
5. Precautions for the use of astronomical telescopes
1. Never watch the sun directly with a telescope. Watching the sun must be done by projection method or special filtering measures.
2. Do not use the telescope as a toy, use and maintain it carefully.
3. Don't think you can see everything with a telescope. The better the viewing effect, the higher the price. There is no perfect telescope. The most important thing is to choose the one that suits you.
4. Every telescope has its proper magnification. Exceeding the limit will not enhance the resolving power, but will make the object very dark and difficult to observe. For telescopes with 60-80 calibers, the appropriate magnification should be less than 100 times.
5. If you can't identify more than five constellations in the night sky, don't rush to use a telescope.
6. Astronomical telescopes can often view landscapes or flora and fauna and can easily get higher magnification than binoculars. But the magnification should be below 100 times, 20-50 times is the most suitable.
*As a beginner, it is recommended not to buy a monocular, at most a pair of binoculars, the larger the magnification, the smaller the field of view.
Buy binoculars with a diameter of 50mm. Choose 7X50 or 10X50 magnification.
6. Eyepiece knowledge
(1) Performance parameters of the eyepiece
The main parameters of eyepiece performance are focal length, field of view and exit pupil distance.
1. Field of view: The current standard eyepieces (such as Plossl and OR type eyepieces, 4 pieces and 2 groups) have a field of view of 40-50 degrees, while wide-angle eyepieces (usually more than 6 pieces) have a field of view of more than 60 degrees, and some can reach 84 degrees. The larger the field of view, the wider the observation range, and the better the observation effect.
2. Exit pupil distance: refers to the distance from the observer's eye to the eyepiece when the entire field of view can be clearly seen. The exit pupil distance directly determines the convenience and comfort of observation. An eyepiece with a moderate exit pupil distance (such as 15-20mm) will bring a lot of convenience to observation. For the same eyepiece, the exit pupil distance is generally proportional to the focal length. If the exit pupil distance is too short or too long, it will bring inconvenience to observation.
3. Equipping of eyepieces: A telescope should usually be equipped with multiple eyepieces so that they can be combined into various magnifications. ①First of all, an eyepiece with a low magnification and a large field of view should be equipped to observe nebula clusters with a large area and low surface brightness. At the same time, it is also possible to find the target first when using a high-magnification eyepiece, which will be the most frequently used eyepiece. The magnification of this eyepiece should be 2-3 times the diameter of the telescope in centimeters. For telescopes with smaller apertures, a Plossl eyepiece with a focal length of 40-55mm (with a field of view of about 40 degrees) is sufficient; when the relative aperture is larger, it is best to choose a wide-angle eyepiece with a slightly shorter focal length (field of view > 60 degrees). ②Medium magnification eyepieces are mainly used to observe deep sky objects such as nebula clusters. A typical medium magnification is 5-10 times the objective diameter in centimeters. ③High magnification is mainly used to observe planets, binary stars, dense nebula clusters, etc. A good quality objective (such as a 10cm APO refractor) should allow the use of eyepieces with a magnification of 25x their aperture in centimeters without appreciably degrading image quality.
(2) Types of eyepieces
1. Huygens eyepiece (H eyepiece)
Designed by Dutch scientist Huygens in 1703, the field of view is about 25-40 degrees. Huygens eyepieces are the first choice for small refractors, but their disadvantages are small field of view, low contrast, chromatic aberration, and obvious spherical aberration field curvature. At present, this structure is generally used in the eyepiece of the microscope.
2. Ramsden eyepiece (R eyepiece)
Successfully designed in 1783, the field of view is about 30-45 degrees, and it is rarely used now.
3. Kellner eyepiece (K eyepiece, RKE eyepiece)
It was developed on the basis of Ramsden eyepieces. It appeared in 1849, with a field of view of 40-50 degrees. It has a comfortable exit pupil distance at low magnification. It is currently widely used in some medium and low magnification telescopes. Underperforming.
4. Abbe distortion-free eyepiece (OR eyepiece)
It was designed in 1880 by Abbe, one of the founders of the German Zeiss company. The eyepiece controls chromatic aberration and spherical aberration, and also has a flat field of view of 40-50 degrees and sufficient exit pupil distance. It has good performance at various magnifications and has been widely used.
5. Prussell eyepiece (PL eyepiece)
Also called "symmetric eyepiece". Its parameter performance is comparable to that of OL eyepieces, with larger exit pupil distance and field of view, lower cost, and suitable for all magnifications. It is currently the most widely used eyepiece.
6. Elephant wide-angle eyepiece (ER)
Successfully developed in 1917, it is specially designed for military telescopes that require a large field of view, with a field of view as high as 60-75 degrees. It performs very well at low power and is especially suitable for observing deep sky objects.
* Common representation methods of eyepieces: The English in front represents the type of eyepiece, and the number in the back represents the focal length of the eyepiece.
PL25 = 25mm focal length Prossel eyepiece
H10 = 10mm focal length Huygens eyepiece
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