What do APO and Ed mean in astronomical telescope? Why do some astronomical telescopes only have APO, some only have ED, and some have both APO and ED?

Ed: It is a low dispersion lens, usually referring to two refracting mirrors, one of which is ED, which is also an intermediate type between apo and common elimination.

Some telescopes are only equipped with APO lens, while others are only equipped with Ed lens. Astronomical telescope can satisfy both APO and ED lenses, so it is different.

Infrared window: the range of infrared band is between 0.7 ~ 1000 micron, and the situation of infrared band is more complicated because of the different infrared wavelengths absorbed by different molecules in the earth's atmosphere. Astronomical research usually uses seven infrared windows.

Radio window: Radio band refers to electromagnetic wave with wavelength greater than1mm.. The atmosphere also absorbs a small number of radio bands, but the atmosphere is almost completely transparent in the range of 40 mm to 30 m. We generally call the range of 1 mm to 30 m the radio window.

The atmosphere is opaque to other bands, such as ultraviolet, X-ray and γ-ray. Astronomical observation of these bands can only be realized after a few days on the satellite.

Extended data:

Ultraviolet band is the frequency range between X-ray and visible light, and the observation band is 3 100 ~ 100 angstrom. Ultraviolet observation should be carried out at the height of 150 km to avoid the absorption of ozone layer and atmosphere. The first ultraviolet observation was to carry a telescope into the sky with a balloon. Later, the use of rockets, space shuttles, satellites and other space technologies made the real development of ultraviolet observation.

The observation of ultraviolet band is of great significance in astrophysics. Ultraviolet band is a frequency range between X-ray and visible light. Historically, the dividing line between ultraviolet and visible light was 3900 angstroms. At that time, the dividing standard was whether it could be seen by naked eyes. The observation band of modern ultraviolet astronomy is 3 100 ~ 100 angstrom, which is connected with x-rays, because the absorption limit of the ozone layer to electromagnetic waves is here.

1968 OAO-2 was introduced in the United States, and TD- 1A was introduced in Europe. Their task is to make a comprehensive investigation of ultraviolet radiation in the sky. OAO-3 was named Copernicus and launched in 1972. It carried a 0.8-meter ultraviolet telescope and operated normally for 9 years, observing the ultraviolet spectrum of celestial bodies from 950 angstroms to 3500 angstroms.

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