Bad Astronomy: Misconceptions and Misuses Revealed, from ...

WELL, WELL 109
it. Two students even used binoculars, which should have helped
by increasing the contrast even more. They failed to see Vega as
well. This is not surprising, really. Vega is too faint. Still, they
showed by direct proof that stars are at least extraordinarily difficult
to see through a chimney.
Another legend bites the dust, or in this case, the soot. While
looking through a narrow opening does increase your ability to see
faint objects, it simply doesn’t increase it significantly enough to
see stars during the day, and that same narrow opening makes it
highly unlikely that a bright star will be in a viewable position.
Still, I have no doubts the legend will persist, as they all do.
Even a friend of mine, an astronomer of no small status, swears
the legend is true. He claims he saw it himself: he once looked up
a long chimney during the day and saw a star. David Hughes, in
his excellent paper entitled “Seeing Stars (Especially up Chimneys),”
notes that a good chimney will have an updraft, even when
there is no fire (Quarterly Journal of the Royal Astronomical Society
24 [1983]: 246–257). It’s possible that my friend saw bits of
debris caught in the draft and briefly lit by the Sun. At a great distance
the debris will look tiny, unresolved, and not appear to move
very quickly. This could be mistaken for a momentary glimpse of a
star. I explained this to my friend, and I explained the idea of a
star’s brightness versus the sky’s surface brightness, and I even
talked about the odds of a bright star just happening to be in that
extremely tiny line of sight, but he would have none of it. He
stands by his story. I guess even the staunchest of scientific minds
can have superstitions they don’t want to drop. It’s an interesting
cautionary tale for all of us, I think.
Now, having said all that, I must confess that it is possible to
easily see one starlike object during the day: Venus. Venus is
roughly 15 times brighter than Sirius, so not only is it possible to
see during the day, it’s also relatively easy. You need to know just
where to look, but it can be done. I’ve seen it myself on several
occasions, in broad daylight. However, extrapolating from seeing
Venus during the day to seeing stars from a chimney is a pretty big
stretch. In the end, the legend turns out to be just that: a legend.
PPP