An astronomical refractive telescope has an objective of focal length 20m and an eyepiece of focal length 2 cm.

The length of the telescope tube is $f_o + f_e = 20 + (0.02) = 20.02 m$
Also, $m=20/0.02=1000$
Also, the real  image formed  by the objective is real and inverted . Tiis real image serves as the object for the eyepiece and the final image formed by the eyepiece is virtual and inverted .