Here is the actual geometry at the equator, ignoring axial tilt (the blue/black circle is Earth, the red/black circle is a satellite at 500km, and the radial lines are hours): https://www.desmos.com/calculator/3br1snafmj

Starlink satellites directly overhead are in sunlight for about 1.5 hours after sunset, and the same before sunrise. Including observing on an angle, you probably lose 4 hours per night out of 12. With 300km satellites, you probably lose 3 hours. I think the situation will be worse away from the equator in summer.