Telescopic camera

Telescope is used to solve the problem of out-of-focus. If you can focus, you don't need an extension tube. Generally, a camera can't focus directly after it is connected to a telescope (without zenith lens), so it needs to be connected to a telescopic tube. But the camera is connected to the zenith mirror, which plays the role of extending the cylinder, so there is no need to extend the cylinder. However, if the camera is connected to the zenith mirror, the optical axis will shift, resulting in poor imaging quality. Generally, in deep space photography, if the telescope can't focus, it is necessary to use adapter ring and extension tube.