How to look at the multiple of the telescope
The multiple of the telescope is the first number, and the last number is the clear aperture. Multiplying these two numbers has no specific effect, it’s two separate parameters.
For example: 20X22 means the magnification is 20 times and the clear aperture is 22mm.
The bigger the telescope multiple, the better?
The multiple of the telescope is theoretically inversely proportional to the field of view of the telescope. The higher the multiple, the smaller the field of view. Therefore, the magnification of the telescope should not be too large. 50MM aperture binoculars, if it reaches 20 times, it basically reaches the limit, if the multiple is large, the field of view is too small. Basically unusable.
Common multiples of handheld telescope< p class='MsoNormal'> Common is 7 times, 8 times, 10 times. 12x or higher telescopes are not technically difficult, but if you don’t use a tripod, it will shake and see nothing.
The maximum magnification of the handheld telescope
1. The handheld telescope has a standard multiple range, that is, between 7 and 10 times. This multiple range is obtained through long-term practice.
Because the multiplier is not as high as possible, while increasing the multiplier, it will also cause problems such as narrow field of view and jitter.
2. ‘How much is the highest’, in fact, the highest is 20 times, 16 times, 12 times, but there is no such thing for regular products, such products are all what? They are all deformed, low-end products that rely on multiples to lure consumers unfamiliar with telescopes.
Buying suggestion for hand-held telescope
For viewing, 6~8 times of binoculars is the best, the eyepiece is between 32~42 times, and the back mirror is used.
For stargazing, 8-12x binoculars are the best, eyepieces are between 42-50, and dorsal mirrors.
Paul’s mirror is not recommended, because of the same diameter, the dorsal mirror is much lighter than the Paul’s mirror, which is more suitable for hand-held and less jitter.
It is not recommended for those over 50, and the weight is also considered. Even if the back is over 50, the back should be 1kg. If you hold it, it will inevitably shake.
How to look at the parameters of the telescope
The magnification of the telescope: the magnification (magnification) of the telescope, which is the magnification when observing the target through the telescope. Observing an object at a distance of 700 meters with a telescope of 10 times is equivalent to observing an object at a distance of 100 meters with the naked eye, and its value is equal to the ratio of the focal length of the objective lens to the focal length of the eyepiece.
Aperture of the telescope: This refers to the diameter of the circular opening of the objective lens, which is usually expressed in mm, such as 7X50, which means that the aperture of this telescope is 50mm.
Telescope focusing methods: Generally speaking, there are two kinds of focusing methods, one is middle focusing, that is, by rotating the focusing wheel in the middle of the mirror body, the two eyepieces are adjusted. The image is gradually clear. There is a separate focusing wheel on the right eyepiece of some telescopes. This is because people’s two eyes do not necessarily have the same vision, so the right eye can be adjusted separately. The method of use is to close the right eye first, and then adjust the middle tone. Focus wheel, open the right eye after the image of the left eye is clear, and adjust the eyepiece of the right eye separately through the focusing wheel of the right eyepiece.
The other is to adjust the focus separately, that is, close the right eye and adjust the eyepiece of the left eye separately. After the adjustment is clear, close the left eye and adjust the eyepiece of the right eye separately. Great view.
Prism System: There are two basic designs for mainstream telescope prism systems: Roof prism or Porro prism.
The advantage of the roof prism system is that the optical structure is relatively light and compact, which is more suitable for outdoor sports portable products; The imaging effect of the telescope has been greatly improved), which requires high assembly precision, is difficult to manufacture, and is expensive. At the same time, the shape is much more complicated than that of the Paul prism, and the processing is difficult. In addition, it is also difficult to assemble and maintain compared to the traditional Paul prism, so the cost is higher.
Paul prism, also known as right-angle prism, is a traditional classic design. The more common design is composed of two identical right-angle prisms. The advantage is that the shape is simple, and the light transmittance and brightness will have a good effect. , It is easy to process and assemble, but the disadvantage is that it is relatively heavy and bulky relative to the roof prism.
Prism material: In terms of prism material, currently in the sales market, the brand name of Schott of Germany is more commonly used internationally, and it is used in two common telescope prisms. The material is BK-7 (SCHOTT’s grade, the approximate material grade of our factory is K9) or BAK-4 (SCHOTT’s grade, the approximate material grade of our factory is K7).
BK-7 or BK-4 are both historically proven cost-effective designs. Comparatively, BAK-4 glass has a higher refractive index and better eliminates internal light scattering losses, resulting in Sharper, brighter images.
Close focus distance: The distance at which the closest object to the observer can be seen clearly, for example, the close focus distance is 3 meters, then the object viewed within 3 meters is blurred, 3 You can see clearly only by adjusting the focus from a distance of meters.
Exit Pupil Diameter: The diameter of the bright spot formed behind the eyepiece after the light rays converge through the eyepiece. For the optical equipment used by the naked eye, the light must pass through the pupil and enter the retina for imaging. The human pupil is about 3mm during the day and up to 7mm at night. When observing with optical equipment, the bright spot formed by the converging light of the eyepiece will be projected on the pupil. Therefore, the larger the diameter of the exit pupil, the brighter the image will appear.
The formula for calculating the diameter of the exit pupil is: p = D / M where p is the diameter of the exit pupil, D is the diameter of the objective lens, and M is the magnification.
Exit pupil distance: The distance between the eye and the last lens of the eyepiece when the entire field of view is seen clearly. Nowadays, many binoculars are designed with long exit pupil telescopes, mainly to be more comfortable to use and to view the scenery brighter, especially for users who wear glasses, they can also be used without taking off their glasses, while some ordinary exit pupil telescopes, wearing glasses basically Difficult to use.
Telescope Field of View: Refers to the extent of the sky that a telescope or binoculars can see. The field of view represents the maximum range that can be observed through a telescope, usually expressed in angle. The larger the field of view, the larger the observation range. The field of view is generally represented by the horizon (observable width) at a kilometer and converted into an angle of view (angle of view). There are three common representation methods: one is to use the angle directly, such as angle of view: 9??; The visible range in meters, such as Field of view: 158m/1000m; the third is the feet at thousand yards used in some foreign countries, which is actually similar to the second, such as Field of vies: 288ft/1000y.
Relative brightness: Relative brightness is calculated by formulas based on multiples, aperture and other indicators. The simple calculation method is the square of the diameter of the exit pupil.
Telescope resolution: The actual resolution of the telescope is generally not more than 20′, mostly within 10′, while the resolution of the naked eye is 60′, so it can be seen through the telescope Objects that cannot be seen clearly by the naked eye.
Telescope Coating: Optical Coating: This is the lowest-level coating, the price is cheaper, generally a mirror-coated single-layer coating, generally coated Objectives.
Fully Coated: All lenses are coated with a single coating. This increases light transmission from 50% to 80%.
Multi-coated: at least A mirror with more than one coating.
Full-mirror multi-coated: This is the most advanced coating. It means that all mirrors are multi-coated to increase the light transmission rate to 90% ~95%.
Telescope Eyecups: There are twist-up and foldable.