The construction of larger, more observable telescopes to use it to spy on the mysteries of the universe is what astronomers have been pursuing. The US Space Network recently published an article that described the construction of the European Telescope as a telescope The largest eye, with an aperture of 39.3 meters, is actually a more meaningful parameter for astronomers than caliber. So, what is the difference between effective caliber and caliber? Which factors affect the effective calibre? size?
'For most astronomical telescopes, the caliber and the effective calibre are not much different.' Fan Zhou, an associate researcher at the Xinglong Observation Station of the National Astronomical Observatory of the Chinese Academy of Sciences told a reporter from the Science and Technology Daily, but for some telescopes with a unique design structure, the caliber and effective caliber are more Big difference.
The caliber usually refers to the maximum physical diameter of an astronomical telescope, and the effective caliber refers to the effective caliber of the mirror that actually receives photons. 'Most of the telescopes, although the mirrors are shielded by sub-mirrors and trusses, are relatively small in area. Therefore, it is basically negligible. 'Fan Zhou said. However, for some special optical design telescopes, the effective aperture and caliber will be quite different. For example, the large synthetic surveying telescope LSST under construction. Although its main mirror is 8.4 m, but due to the special optical design, the central part of the main mirror is actually a 5 meter third mirror, so the actual effective diameter is only 6.68 meters.
The general radio telescope is also similar to the optical telescope. However, some special radio telescopes are not. For example, FAST is the world’s largest single-antenna radio telescope. It is like a huge eye, set in the south of Guizhou Province. This is also the difference between it and most telescopes - FAST's 'base' cannot be rotated as a whole.
The general astronomical telescope is equipped with a device called a theodolite. It is like a usual mirror base, which can rotate the telescope 360 degrees. When observing the star in the continuous movement of the east, the 'pedestal' can Holding the mirror with the stars together to keep track of the exposure.
There is no 'pedestal' to do. This is to say FAST's 4443 reflector panel. 'FAST's real-time tracking of celestial bodies is done by paraboloids consisting of these sub-mirrors.' Jiang Peng, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, said: Think of FAST as a large bowl. Inside it is a parabolic mirror with a smaller diameter than the bowl mouth, which is tracked as the position of the observation target moves. The effective diameter is the diameter of the parabolic mirror.
'Mirror splicing and control accuracy are also factors that affect the effective caliber of the telescope.' Jiang Peng said that to achieve a combination of parabolic confocal phasing, see celestial bodies more clearly, see more distant and faint celestial bodies, which requires very precise technology Ability to grasp.
At present, the maximum diameter of a single-surface optical telescope that can be manufactured by human beings is about 8.4 meters. A telescope with a diameter larger than this value needs multiple mirrors to complete the mosaic. In the process of manufacturing and debugging the Great European Telescope in the future, the precision of the mirror surface mosaic is improved. Will be an important step in the use of its observation capabilities.
