refractive telescope 1. This device uses two or three convex lenses or one convex lens and one concave lens to form reflection through refraction. 2. The color of the reflection in this device is defective. 3. The reflection has spherical errors. 4. As the absorption of light increases, the brightness of the reflection decreases. 5. It is difficult to prepare large-scale lenses for instruments. . The scattering capacity is low. Reflector telescope 1. In this device the image is formed by reflection using a concave and a plane or two concave or a concave and a convex mirror. 2. The color of the reflection in this device is not defective. 3. Spherical errors of reflection can be eliminated. 4. The lower the absorption of light, the brighter the reflection. 5. It is relatively easy to make mirrors for large children. . The scattering capacity is high.