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hhEb09'1
2005-Oct-01, 01:44 PM
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 (http://www.bautforum.com/showthread.php?t=32983), a couple of posters make contrary claims. Dimmer stars were visible without resorting to light cutouts. Anybody else have any experience with this?

ngc3314
2005-Nov-01, 09:21 PM
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 (http://www.bautforum.com/showthread.php?t=32983), a couple of posters make contrary claims. Dimmer stars were visible without resorting to light cutouts. Anybody else have any experience with this?

I'm one of the contrarians, so maybe I should be disqualified - but the claim being made in the other thread was that from very clear locations, with unusually clean skies, experienced observers who have carefully worked out just where to look can on rare occasions just make out stars as faint as magnitude 0 with the sun (sometimes just slightly) above the horizon. I'm not sure that should be seen as a refutation of "unprepared observers at the bottom of a well would not see stars overhead". If nothing else, there are only about half a dozen such stars (and five planets that would occasionally make it, although Mercury is really too close to the Sun in our sky when that bright and Mars has to be near opposition with very limited daytime visibility). The odds of one of these bright objects being in the right place (on top of to omuch dark adaptation, etc.) are really small.

hhEb09'1
2005-Nov-02, 05:59 PM
I'm not sure that should be seen as a refutation of "unprepared observers at the bottom of a well would not see stars overhead". But it appears that the BA was discussing prepared and knowledgeable observers.

I'd still like to hear particular personal incidents, if anyone has any.

hhEb09'1
2007-Oct-17, 04:36 AM
Any takers?

We've had some more discussions about this, right?