Magnification
Generally, the ratio of the angle of view of the eyepiece to the angle of incidence of the objective lens is used as an indication of the magnification of the telescope, and the ratio of the focal length of the objective lens to the focal length of the eyepiece is usually calculated to indicate the magnification of the telescope's viewing angle. For example, a telescope with a magnification of 10x refers to a target that can magnify a 1-degree field of view to 10 degrees.
Field of view
(Field of view) is marked with the range of the visible scene of the product at 1000 meters, such as 126m/1000m, indicating that at 1000 meters from the observer, the telescope can observe a field of view within 126 meters.
Exit pupil diameter
are parameters that roughly describe the brightness of the image. In low-light environments, larger pupil diameters can result in clearer images. The human pupil, under normal physiological conditions, will not exceed 7mm, so the diameter of the pupil greater than 7mm is unintentionally a waste of light. This parameter cannot fully reflect the quality of the telescope, because this parameter, as long as it meets the manufacturing specifications, can meet the numerical requirements. The larger the pupil diameter, but there is another benefit: the larger the pupil diameter, the more suitable for use in a bumpy environment, and the observation picture will be more stable, so telescopes of such specifications as 7X50 are mostly suitable for marine use. This value can be obtained by dividing the objective lens diameter by the magnification.
Resolution
Resolution (called explainability in Hong Kong and Taiwan) is the precision of the screen image, which refers to the number of pixels that the display can display. Since the points, lines and surfaces on the screen are composed of pixels, the more pixels that the display can display, the finer the picture, and the more information can be displayed in the same screen area, so resolution is one of the very important performance indicators.
Dusk factor
Published by Zeiss Optics. It reflects the observation efficiency of telescopes of different apertures and magnifications in low-light conditions. Calculation method: The product of the telescope's magnification and aperture is squared.
Effective caliber and relative caliber
The distance from the center of the objective to the focal point is called the focal length of the objective and is indicated by the symbol F. The part of the objective whose diameter is not obscured by the frame and diaphragm is called the effective aperture of the crop lens, which is indicated by the symbol D. The performance of astronomical telescopes is mainly marked by these two data.
Light collector
In the dark, the pupil diameter of the human eye is generally about 7mm. Therefore, the multiple of the effective area of the telescope objective relative to the pupil area is called the light gathering force. That is: light collection force = (D*D)/(7*7), where D is measured in millimeters.