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chaboyax
2009-May-21, 05:19 PM
i work with this nice older gent who swears that during a very long hot summer in the uk around the mid 1970s there was about 1 week where you could see quite a few stars in the sky even at noon.does any one know if this is possible and howthat happens.i keep thinking that the clearer the sky in the daytime the brighter it would be there for less chance of stars being visable. thanks in advance

antoniseb
2009-May-21, 05:37 PM
I've seen Venus, Jupiter, and Sirius in broad daylight (close to noon). In each case, the sky was *very* clear AND I was in the woods, so I could stand in the shade, but see selected spots in the sky. Venus I saw by accident this way. After that I started trying to see other objects.

NEOWatcher
2009-May-21, 05:39 PM
i work with this nice older gent who swears that during a very long hot summer in the uk around the mid 1970s there was about 1 week where you could see quite a few stars in the sky even at noon.does any one know if this is possible and howthat happens.i keep thinking that the clearer the sky in the daytime the brighter it would be there for less chance of stars being visable. thanks in advance
I have no clue myself. But with normal conditions it takes around a mag -7 to see in daylight (judging by Iridium flares) I could probably stretch that, but we are still talking about 10 times brighter than Sirius.

I would think that as the sky becomes clearer, they would be easier to see. It's the scattering of the non-clear sky that blocks our view. The brightness only comes in to play as you come into view of the sun and it's glare.

I would doubt it, but I've been surprised before.
[EDIT]
See; mentioned as I typed this.
For a followup, I wonder if this could have to do with latitude? Like, since the sun is a bit lower in the sky, etc.

Swift
2009-May-21, 05:45 PM
Well, during almost any clear day around noon you can see at least one star in the sky (you know, the one about 8 light-minutes away). ;)

NEOWatcher
2009-May-21, 05:47 PM
Well, during almost any clear day around noon you can see at least one star in the sky (you know, the one about 8 light-minutes away). ;)
Good thing you specified "clear" day. Otherwise, I'd make some snide remark about NE Ohio.

George
2009-May-21, 06:04 PM
i work with this nice older gent who swears that during a very long hot summer in the uk around the mid 1970s there was about 1 week where you could see quite a few stars in the sky even at noon.does any one know if this is possible and howthat happens.i keep thinking that the clearer the sky in the daytime the brighter it would be there for less chance of stars being visable. thanks in advance The trick is finding them even if you know they're there. It helps enormously to have another object to serve as a reference location for you. There are several ways to do this.

chaboyax
2009-May-21, 09:09 PM
cheers swift i kinda guessed after i posted someone would say that or the like

George
2009-May-21, 09:20 PM
cheers swift i kinda guessed after i posted someone would say that or the like Yeah he beat me, that's why we call him swift. ;)

chaboyax
2009-May-24, 10:55 AM
so other than the sun and planets (maybe)do any of you think this is true or has this guys age caught up with him

Paul Beardsley
2009-May-24, 11:19 AM
By way of additional information, the summer in question would be 1976. I was 13, and really, really into astronomy. I do remember pointing out some stars to my mother - Vega, Deneb, Altair - but this was in the evening. However, I do recall that it felt like daytime because it remained warm even when the sun had gone down. Could this be a clue to your friend's confused memory?

neilzero
2009-May-24, 12:53 PM
Generally you need some equipment, such as a forest or a small gap in dark clouds even to see Jupiter in daylight around noon. This is partly because your eyes let in very little light under very bright conditions. I understand a telescope with CCD = charge coupled device will see many stars in the day time if you turn the contrast up until it starts making artifacts. Neil

cbacba
2009-May-24, 04:47 PM
I've seen Mercury in the latter afternoon but still an hour or more before sundown. Finding it was almost impossible as the eye wanders and has focus problems when there is nothing to latch onto so the object often remains unseen as the eye sweeps past its position.

I've also seen images taken during the daytime of brighter objects, like Sirius. It's really just a matter of how bright the sky is, scattering etc. versus how bright the object is. Suffice to say that the quality suffers terribly and the only exception of an improvement is with Mercury images taken when high in the sky - using videoastronomy techniques. I expect using narrow band filters at longer wavelengths would potentially help quite a bit, at least for some objects.

stu
2009-May-24, 08:54 PM
I'm fairly sure you can see about half a dozen of the brightest non-Sun stars during the day. Sirius is the most obvious. I want to say that Phil covered this in his Bad Astronomy book, but I'm on vacation at the moment and can't look it up.

grant hutchison
2009-May-24, 09:33 PM
I'm fairly sure you can see about half a dozen of the brightest non-Sun stars during the day. Sirius is the most obvious. I want to say that Phil covered this in his Bad Astronomy book, but I'm on vacation at the moment and can't look it up.He did. He reports experiments which predict that the dimmest "star" a person could see in broad daylight is five times brighter than Sirius. That's easily attainable for Venus, but brighter than Jupiter and Mars.
If you restrict your view of the sky, you can do better: about half as bright as Sirius if you're viewing it through only a small patch of sky. So Venus, Jupiter, Mars, Mercury and Sirius are possible; Canopus marginal. That's the half-dozen Phil mentions in the book.

Grant Hutchison

ngc3314
2009-May-24, 09:47 PM
In very clear locations, I've managed Sirius, Jupiter, Vega, and Arcturus before sunset (in younger days when my eyes focussed better). One thing that really helps is finding a location where the object will align so you can find it - corner of building if you backtrack from where it is when just getting dark, or the Moon adjacent. I also vaguely recall a study that scattering of light in the eyeball brightness the sky background by more than 2x, so restricting the field of view should help as long as it doesn't trigger a change in the brightness adaptation and thus dazzle the view.