What is the farthest distance at which we can see an astroid when it subtends the smallest angle we can resolve from the ground under normal conditions?  If the astroid is 20 km across, and subtends an angle of 0.7 arc sec., then we can divide the angle in two, and form two right triangles within the subtended angle, using the astroid as the side opposite. The Green triangle in the above drawing will have an angle of 0.35 arc sec., and the side opposite that angle is 10 km. so its baseline, x will be:
x = 10 / tan (0.35 / 3600) = 5,893,280.179 km
A 12" clear aperture mirror used beyond our atmosphere has a resolving power of 120 / (25.4 * 12) = 0.38 arc sec and would allow us to see the same object with the same clarity from a distance of 10 / tan (0.19 / 3600) = 10,856,042.43 km. In space, astroids are called astroids, but when they enter our atmosphere they become meteors. Their landed remnants are called meteorites. Meteorites have three Chondrite classes: H, L, and LL, with densities of 3.8 g/cm$$³, 3.75 g/cm³, and 3.54 g/cm³ respectively. Knowing the density and volume of an astroid, - we can calculate the astroid's mass.