At its "Maximum Viewing Distance" 5,893,280.179 km or 5893280.179 / 149.598 X 10$$⁶ = 0.03939411 AU, no detail smaller than 20 km can be resolved. A second object of the same size must be separated from the first object by a distance of 20 km in order for both objects to be distinguished as two separate objects from this distance. The larger the object, the farther the Maximum Viewing Distance.
Beyond this distance the astroid may be seen as a point source of light. Here the surface detail disappears but the object's reflected light remains visible.
All telescopes have three powers: Light Gathering Power, Resolving Power, and Magnifying Power. The maximum practical Magnification is limited to a telescope's Resolving Power. Since the telescope's Resolving Power is limited to 0.7 arc sec., and since this is the equivalent Resolving Power of a 6.75" Space based telescope, the maximum magnification used should not exceed 2 * (25.4 * 6.75) = 342.9 X because any larger magnification will fail to reveal any new detail.

Light Gathering Power is the only power truly limited by the size of the objective in ground based telescopes. The larger the better. Here the telescope's Full Aperture forms the light gathering area whether or not the entire aperture is useful in forming a coma free image. In this regard, there is no difference between a true parabolic reflector and a paraboloid. This power is calculated as LG = (A / p)$$² where A is the telescope's aperture in millimeters, and p is the entrance pupil of a dark adapted human eye.  Thus all my 14" telescopes have an LG that is (14 * 25.4 / 7)$$² = 2580.64 X brighter than the unaided eye.
When you look into a telescope for the first time, you see thousands of stars that were not visible before. It is very impressive, and it is the Light Gathering Power that impresses most.  Now we need to know how bright an object must be to be detectable at any given distance from by my telescope. I don't need to see the object as long as I can glimpse its reflected light.