How Do I Choose the Best Cassegrain Telescope?

Cassegrain Telescope: A reflecting telescope composed of two mirrors, invented by Cassegrain in 1672. The larger one is called the main mirror and the smaller one is called the secondary mirror. A hole is usually made in the center of the main mirror and imaged behind the main mirror. Its focus is called the Cassegrain focus. Sometimes, an oblique plane mirror is added as shown by the dotted line in the figure, and the image is on the side. This Cassegrain telescope is also called a Nesmus telescope.