For some "average sized" black hole, how long would it take for a distant (spacesuit-wearing!) astronaut to:
- be able to see the gravitational lensing with the naked eye
- clearly feel the gravity gradient
- reach a lethal gravity gradient
- cross the event horizon
Ultimately I'm interested in the subjective experience of a human falling into a black hole. Would it be drawn out and unpleasant? Or is it that by the time the gradient would be painful, there'd be barely any time at all before annihilation?