Product Case Studies

The Cassegrain telescope is a common design of a reflecting telescope that uses a primary mirror (usually a concave parabolic mirror) and a secondary mirror (usually a convex hyperbolic mirror) to focus light. The main advantage of this design is that it can provide a longer focal length while the telescope itself is relatively short, which is achieved through the reflection of light inside the telescope.

The following is a detailed introduction to the Cassegrain system reflector:

Primary Mirror

1. Shape：The main mirror is usually a large diameter concave parabolic mirror. The parabolic shape can focus parallel light rays (such as starlight) from a distance onto a focal point.
2. material：The material of the main mirror is usually glass or glass ceramic, such as low expansion coefficient materials such as Zerodur or Pyrex, which can remain stable under temperature changes.
3. process：The processing of the main mirror requires very precision to ensure that its surface shape meets the design specifications. This includes rough grinding, fine grinding, and polishing processes, as well as possible ion beam polishing or other high-precision surface treatment techniques.
4. paint-coat：In order to improve reflectivity, the surface of the main mirror is usually coated with one or more reflective coatings, such as aluminum or silver, and covered with a protective layer to prevent oxidation.

Secondary Mirror

1. shape：The secondary mirror is a smaller convex hyperbolic mirror that reflects the light focused by the primary mirror back to the focal position near the central hole of the primary mirror.
2. position：The secondary mirror is located on the optical axis of the primary mirror and is usually fixed in front of the primary mirror through a bracket.
3. adjust：The position and angle of the secondary mirror can usually be adjusted to accurately align with the focus of the primary mirror.
4. paint-coat：Like the primary mirror, the secondary mirror is also coated with a reflective coating to increase its reflectivity.

optical system

1. light path：In the Cassegrain system, light is first focused by the primary mirror and then reflected by the secondary mirror to the focal point at a hole in the center of the primary mirror. This design not only provides a long focal length, but also makes the entire system more compact due to the folded light.
2. focal length：The effective focal length of the Cassegrain system is usually much greater than the physical length of the telescope, which is achieved by selecting appropriate primary and secondary mirror curvatures.

Advantages and disadvantages

• advantage：The main advantages of the Cassegrain system are its compact design and long effective focal length, making it highly suitable for observing planets and deep space celestial bodies. In addition, a closed tube can protect optical components from dust and pollution.
• disadvantage：Secondly, mirrors may cause some light loss and diffraction, which may affect image quality. In addition, the precision machining requirements for non spherical surfaces result in higher manufacturing costs for Cassegrain systems.

The Cassegrain system has been widely used in both professional and amateur astronomy due to its unique design and excellent imaging performance.

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