Re: Urban Fables: Stellar by Sunlight

[Michael Bowen <fizzbowen@MINDSPRING.COM>]

At 15:34 2002/03/22, Brian Whatcott wrote:

> So the debunking of daytime planetary sights is the urban fable after all.
> This would have just been amusing, until I realised that there have been
> many many people with telescopes capable of pointing at the brightest point
> object in the sky by daylight for many years - but I never heard of a
> confirmation before....
> (You apparently don't need a telescope to see the effect, but you do need
> to know where to look.)

Yes, it is possible. I suspect from my experience, however, that the
conditions must be just so.

I viewed Venus during daylight some years ago from the floor of
California's Yosemite Valley (elevation about 1300 m). Having seen Venus
very clearly at a large elongation from the sun the previous evening, I
looked for it in the late afternoon and actually did not have too much
trouble spotting it against the deep blue coloring of the sky. (Oops, I
almost said "blue background" there, but that's not quite accurate,
although the illusion was strong.)

My uncorrected vision is between 20/30 and 20/40, and thus barely
sufficient to pass my driving test without correction. At the time, I did
have a pair of eyeglasses that corrected my vision to 20/20. Interestingly,
I was able to locate Venus repeatedly (after turning my head away and then
back) while wearing the glasses, but never succeeded in doing so with the
glasses removed (although I tried several times, alternately removing and
then replacing my glasses while keeping my head tilted in the right
direction). So I actually had two surprises that day; first, that Venus was
definitely visible in full sunlight, and second, that only a slight
degradation of my visual acuity would render it effectively invisible
again. By the way, I don't have astigmatism; I'm just a bit myopic.

--MB