Hubble's slew rate (the rate at which it can change the broad direction its camera points) is about 6 degrees per minute [1], or about 1/10 of a degree per second (I refuse to use the incredibly cursed unit "minutes per second"). It tracks a fine object slower than that, but that gives a reasonable order-of-magnitude estimate.

At even 1 AU of distance, an angular velocity of 1/10 of a degree per second requires a linear speed of about 0.87c. Needless to say, 3I/ATLAS is not moving that fast - if it were, it would be outputting about 100 TW, mostly as heat, just from slamming into the interplanetary medium at relativistic speeds [2].

[1] https://www.pbs.org/deepspace/hubble/diagram.html#:~:text=Th...

[2] https://www.wolframalpha.com/input?i=%2840+*+mass+of+hydroge...