1. Optical aperture: A graphic frame that restricts the light energy through a telescope (usually a spectacle lens) is called the incident pupil (the pupil), which is the aperture D of the telescope objective.
2. Amplification (magnification)
The magnification is the ratio of the angle to the angle of the object as seen by the telescope and the eye when the object is directly visible. If the focal length of the lens and eyepiece is known, it can be amplified by the focal length f of the lens and the focal length F of the eyepiece:
The magnification of the telescope can also be obtained by dividing the diameter d of the incident pupil by the diameter of the ejection pupil, namely:
The larger the magnification, the clearer the general observed object. The basic performance of binoculars is usually numerically expressed on its outer cover, such as: Ix42 the 1th digit indicates that the magnification of the telescope is 8 times times, and the latter number indicates that the aperture of the objective lens is Siam 42 mm.
3. Field of view: The range of objects seen when the eye is observed in the pupil point is called the field of sight. Wide-angle or ultra wide-angle telescopes (field of view greater than 60 degrees) are more observational than the general telescope. The field of view of a binocular telescope is generally expressed on its exterior, for example, 122/1000 means to observe with a telescope, and a field of 122 meters in diameter can be observed at a distance of 1000 meters. Sometimes it can be expressed in feet and angles.
4, resolution: the resolution of the telescope with the object it can distinguish infinitely far two points to the telescope lens center of the angular ∝ representation (in seconds). The resolution of the telescope is directly related to the diameter of the incident pupil. The larger the diameter of the incident pupil (generally the aperture of the objective lens), the higher the resolution of the telescope, the clearer the observed object.
5, the ejection pupil diameter: The incident pupil in the eyepiece behind the image called to make the pupil. After the ejection pupil is located in the eyepiece, the telescope's full field of view can be observed only when the eyes coincide with the ejection pupil. The larger the diameter of the ejection pupil, the higher the subjective brightness of the object is observed with a telescope. Accordingly, a telescope with a large ejection pupil diameter is observed in the evening and in weaker light. The telescope's ejection pupil diameter equals the incident pupil diameter d divided by the magnification of the telescope R: Dad R
6, out of the pupil distance: out of the pupil to the eyepiece close to the eye of the last surface of the vertex distance is the distance between the pupil. The ejection pupil distance is more than 16 mm often called the long out pupil distance, it is easy to wear glasses observation.
7. Transmittance: The telescope's transmittance affects the brightness of the observed object. The transmittance is related to a variety of factors, such as the absorption of glass light, the reflection loss when optical surface is transmitted, light scattering, etc. In particular, the reflection loss during the transmission of optical surface influences the maximum transmittance and also affects the clarity of imaging. Therefore, the telescope's optical lens and air contact surface are to reduce the reflective film (antireflection film). The optical transmittance of the coated film is different (the single layer transmittance is about 50%, the Double-layer transmittance is about 65%, the multilayer membrane transmittance can reach more than 85%), and the coating effect is the best. However, the price factor is generally only in the number of optical parts or in the more high-end telescope plating broadband antireflection film. Judging by the characteristics of a telescope, you can observe the reflection of the lens, if the reflection is serious, the transmission is poor, the image is blurred.