507
xkcd #2849: Under the Stars
(imgs.xkcd.com)
Alt text:
If you live in Los Angeles (around 33°52'N, roughly the latitude of Hermosa Beach) the black hole in V404 Cygni passes over you each day. On Christmas Day it will be directly overhead around 2pm.
I'm glad Asimov also thought of The Long Street or Eternal Dusk I wondered how wide the strip of settleable territory might be, say on a earth-sized tide-locked planet.
The moon is tide-locked to the earth, but wobbles back and forth, so a tide locked world might also have a day / season cycle where the fringes get extra hot / cold.