There are two types commonly available from commercial manufacturers: lens-based refractors, two to five inches (5 to 13 centimeters) in diameter, and mirror-based reflectors, four to 12 inches (10 to 30 centimeters) in diameter.
Det finns två sorter som man i allmänhet kan skaffa sig i handeln: linsbaserade refraktorer, 5 till 13 centimeter i diameter, och spegelbaserade reflektorer, 10 till 30 centimeter i diameter.jw2019 jw2019