To solve this problem it is necessary to apply the concepts related to optical magnification (is the process of enlarging the apparent size, not physical size, of something.). Specifically the angular magnification of an optical telescope is given by
[tex]M = -\frac{f_o}{f_e}[/tex]
Where,
[tex]f_o =[/tex] Focal length of the objective lens in a refractor
[tex]f_e =[/tex] Focal length of the eyepiece
Our values are given as
[tex]f_o =[/tex] 71cm
[tex]f_e =[/tex] 2.1cm
Replacing we have
[tex]M = -\frac{f_o}{f_e}[/tex]
[tex]M = -\frac{71}{2.1}[/tex]
[tex]M = - 33.81[/tex]
Therefore the magnification of this astronomical telescope is -33.81
