This is showing the size difference between two scopes. The smaller one is the Takahashi FSQ106N Astrograph, it’s a 4.17” f/5 530mm quadruplet double ED Petzval. . The larger one is the TEC APO180FL f/7. This is a 7” 180mm and has a native focal length of 1260mm, it has a theoretical resolution of 0.66 arc sec.