The primary mirror is 7.8 feet (2.4 m) in diameter while the secondary mirror is only 12 inches (30.5 cm) wide. The primary mirror can collect 40,000 times more light than the human eye.
Hubble Telescope (NASA)
The Mirror Based Optical System of the Hubble Space Telescope collects and focuses light to analyze it from space. With the help of an optical system called the Optical Telescope Assembly (OTA), Hubble collects infrared, visible, and ultraviolet light, taking a stunning picture of the universe (Space).
The OTA has a graphite epoxy structure, which is found in golf clubs, bicycles and tennis rackets. The graphite epoxy for the OTA frame was chosen because it is very light and strong. However, graphite epoxy shrinks and spreads due to temperature fluctuations. Hubble experiences a change in temperature during the Earth’s orbit.
How does a photo make up with light?
Temperature fluctuations can potentially cause disturbances in the Hubble mirror, so they are kept at a fixed temperature of around 70 ° F (21 ° C). Now the question is how does Hubble capture the light? For this, Hubble uses two mirrors, which are placed in the Cassegrain telescope design to collect and focus light. When the light goes down the length of the telescope, it collides concave and with the primary mirror.
The light collides with the primary mirror and returns to the front of the telescope. Here he collides with the secondary mirror which is convex in shape. The secondary mirror focuses the light into a beam from where the light goes backwards and then through a hole in the primary mirror. After this, light is analyzed with the help of scientific instruments. Hubble mirrors are more curved than parabolic cassegrain mirrors. It is called Ritchey-Chrétien Design which helps to get the best picture of the big scene.
The capacity of the primary mirror is 40,000 times more than the eye
The primary mirror has a diameter of 7.8 feet (2.4 m) while the secondary mirror is only 12 inches (30.5 cm) wide. The primary mirror can collect 40,000 times more light than the human eye. Although the primary mirror is quite large in size, but its weight is extremely light. Instead of a solid core, Hubble’s primary mirror has a ‘Honeycomb Core’, which reduces its weight from 8000 pounds to 1800 pounds.
Both mirrors are covered with thin layers of aluminum and magnesium fluoride. The aluminum layer is 3 / 1,000,000 thick of an inch. The magnesium fluoride layer is plated over aluminum to protect it from oxidation as well as to increase the reflectivity of ultraviolet light. Mirrors and layers are very smooth.
Why is Hubble able to take better pictures?
Hubble is able to take pictures with greater accuracy than Earth telescopes because the Earth’s atmosphere does not get obstructed in its path. The atmosphere obstructs light and blurs photos taken from space. Due to its position outside the atmosphere and powerful optical equipment, it is able to take pictures that telescopes could not take from the earth.
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