Stars in daylight
Subject: Stars in daylight
From: Peter Fogg (ffive@XXX.XXX)
Date: Tue Apr 02 2002 - 22:28:37 EST
Yes, my immediate thought was of the view from the bottom of the well. But I
still don't get it, apart from the lack of deep wells on B52s (at least
vertically), the reason stars are invisible in daylight is that the sunlight
scattered through the atmosphere - effectively flare - is way way brighter than
the stars (possibly the well acts like a long lens shade, masking out some
flare).
Some noise. The Moon and sometimes Venus are visible in the morning and
afternoon under certain conditions, but the system discussed tracked 2 stars
continuously 'and this was in bright sunlight' and I would have thought that
'under a hazy sky' would be even more difficult.
Its a very impressive trick. Maybe the 'little sleight of hand' is classified
information.
Of course, being able to make star sights during the day, especially under hazy
conditions, would be an enormous boon to navigators. It would negate, to a some
extent, the biggest drawback to Celestial Nasvigation - the vagaries of
weather.
The ideal, do everything digital sextant being discussed would be great too,
but given the choice it would be a no contest - daylight star sights - Yes
Please! - where can I sign?!
call me Perplexed
Brian Whatcott wrote:
> At 11:35 AM 4/2/02, you wrote:
> >Paul Hirose wrote:
> >'This system absolutely would track stars in broad daylight, even under
> >a hazy sky.' also 'and this was in bright sunlight.'
> >
> >How did it manage to do this?
>
> I'll try for a response to this:
> There was an urban myth, popular in the years 1990-1994, that
> the ability to see stars in daylight from the foot of a well was an
> urban myth. It turns out, that if you know exactly where to look in
> daylight, and have reasonable acuity you can see Venus by day, if the
> atmosphere is not too milky with moisture. Venus is the brightest point
> object.
> There are a few other brightish objects, which have more difficulty
> competing with daylight scatter. It is possible however, with a little
> sleight of
> hand, to sense signals which are submerging, even well down, in the 'noise'.
>
> It will be this method that allows a fix on day light stellar objects.
>
> Brian Whatcott
> Altus OK Eureka!
