I thought we'd talked about this section (Well, Well: The Difficulty of Daylight Star Sighting, p.103-110 in Bad Astronomy) of the book, but a couple of searches of the forum Bad Astronomy: The Book with "magnitude" or "daylight" or "daytime" didn't turn up anything.

The BA says (p.107) "They determined that if you can cut out all but a tiny fraction of the sky, you can actually see stars that are about 10 times brighter[?] than if seen in the whole sky--in which case it's just possible to see Sirius during the day, but that's it. The next brightest star, Canopus, is on the borderline of detectability. Let's be generous and say that both stars can be seen this way."

The "way" that is being discussed is like from the bottom of a narrow chimney, for instance. However, in this recent thread, a couple of posters make contrary claims. Dimmer stars were visible without resorting to light cutouts. Anybody else have any experience with this?