Theoretical knowledge of telescope multiples
This part only needs to be understood a little bit, it doesn’t matter if you don’t understand it.
The magnification of the telescope is the angle magnification of observing an object with the naked eye and observing the same object at the same place with the telescope. For example, if the angle of a bird is 6 arc minutes to the naked eye, and 60 arc minutes is observed with a telescope, the magnification of the telescope is 10 times.
The above is the theoretical explanation. The most straightforward explanation is that an object with a height of 0.1 meters can be seen with the naked eye, and a telescope with a 10x magnification can see a height of 1 meter. That’s it.
How is the magnification of the telescope calculated? (This part does not actually need a very accurate understanding)
Multiplier = focal length of objective lens / focal length of eyepiece.
If the telescope does not indicate the focal length of the objective lens, you can actually measure it. For example, measure the diameter of the sun’s image and calculate it based on the sun’s focal length of 8.7mm per meter. In addition, the focal length of the objective lens can generally be estimated from the length of the lens barrel. For some telescopes with special structures, the light path may be refracted by the internal prism or flat mirror, which will shorten the length of the actual lens barrel. The roof-shaped refraction is not easy to observe even from the outside. The light path of the reflex optical system is completed in the body of the lens and cannot be seen from the appearance. Observed on.
Knowledge of telescope multiples
The magnification of telescopes is generally divided into three levels: medium magnification (6-10 times), large magnification (10-20 times) and variable magnification (German 20-40 times, domestically produced 25-40 times). The larger the magnification of the telescope is not the better. If the magnification exceeds 10 times, it should usually be mounted on a tripod. If it is only used with an arm, the tremor of the hand will have a serious impact on the observation and the observation effect will be worse. In addition, when evaluating the selection of telescopes, the geometrical optical power should also be considered. Generally, a small optical power telescope (exit pupil diameter of 2-3mm) is suitable for use under good lighting conditions; medium optical power (exit pupil diameter of 3-4mm) is suitable for use under general lighting conditions; high optical power (exit pupil (Diameter is 4-6mm) is not only suitable for daytime use, but also suitable for use under low illumination conditions at dawn and dusk.
Tags: outdoor telescope
refractor