51° N. I'm also on the fourth floor of a building, so the horizon is farther away. I'm exaggerating a little bit. By "still up" I really mean it's still bright enough out, twilighty, that it would affect my ability to sleep. Bedroom window also faces east west, so, yeah it's a combination of factors but still.
I grew up 2 blocks from a train station that would start running routes every 10 min starting at 5:30 or so. Oh boy I can't believe I slept through it as a kid, I wouldn't be able to now without re-acclimating.
For me it’s a sleep mask, but I also understand that that misses the gentle wake up part. But I love that I can bring my sleep mask anywhere which you can’t do with curtains