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View Full Version : Daylight Star Viewing? Myth or Reality?



Astroquest
2002-May-12, 09:56 PM
This is an old question many kids have asked over the years (similar to the Coriolis water swirl question). If you are in deep dark well or hole in the ground, can you look up and see stars during daylight hours with full sunshine and a clear sky? Bad Astronomy or not? I've searched the site and did not find a post on this question. I've heard intelligent adults debate this issue and have heard interesting comments, pro and con! What do you think or know?

Jim
2002-May-13, 01:04 AM
The BA addresses this in his book.

Short answer, no.

The thinking goes that there is less light at the bottom of the well and your eyes adapt so they can then see the faint light of the stars when you look up. But if your eyes adapt to the lower light at the bottom of the well, this makes them more sensitive to the light in the sky which you see when you look at the top of the well.

Kizarvexis
2002-May-13, 01:34 AM
I watched a shuttle launch just after dawn once. As the plume from the engines spread out, it blocked some of the dawn sunlight. A very narrow strip of sky became darker and it may have been possible to see stars. I don't remember if we saw any. It was about 7 years ago. Of course this was vastly different than being down a well as the exhaust plume from the shuttle is quite tall.

I beleive you might see stars during an esclipse. Would that count as daylight?

Kizarvexis

Astroquest
2002-May-13, 01:34 AM
Thanks for the post. The book by BA sounds good.

<font size=-1>[ This Message was edited by: Astroquest on 2002-05-12 21:38 ]</font>

Astroquest
2002-May-13, 01:55 AM
I agree the brighest stars would be visible with a total solar eclipse but probably not an annular (ring-shaped) or a partial eclipse.

Thanks

roidspop
2002-May-13, 02:51 AM
It is entirely possible to see Venus in broad daylight when it is at its brightest. I have had the pleasure of showing scores of kids this surprising sight at noon (of course, we were in the western mountains at about 7000 ft with desert skies overhead, but hey). I don't have an astronomy program, but I'm sure somebody here could tell you when Venus will next put in a suitable appearance for such an attempt. As to stars...fuggedaboutit.

David Hall
2002-May-13, 03:13 AM
I've seen several partial eclipses (78% once) and one annular eclipse, and no, it doesn't get dark enough to see stars. It gets a little like the dusk just before dark though. But it's also unlike dusk, so it's rather a creepy feeling.

A few of the brightest stars and planets are visible in daylight, but you have to know exactly where to look, or else the general sky brightness drowns them out. I've seen Jupiter and Sirius in the daytime myself. Looking out of a hole doesn't change the brightness of the general sky glow.

This seems like a good place to mention that I found an example of this very error in a famous book: The Lord of the Rings.



Light grew, and lo! the company passed through another gateway, high-arched and broad, and a rill ran out beside them; and beyond, going steeply down, was a road between sheer cliffs, knife-edged against the sky far above. So deep and narrow was that chasm that the sky was dark, and in it small stars glinted. Yet as Gimli after learned it was still two hours ere sunset of the day on which they had set out from Dunharrow; though for all that he could then tell it might have been twilight in some later year, or in some other world.


This is from "The Passing of the Grey Company" in Return of the King. I wonder if they'll put it in the movie? /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_wink.gif

David Hall
2002-May-13, 03:35 AM
Actually, the answer to this question should be easy to understand on your own. Just imagine standing at the bottom of a well and looking up. What do you imagine you'll see? I simply imagine a circle of blue sky above me. I can't even force my imagination to realistically let me see stars in that image.

Also, in answer to Roidspop's wonderings, Venus never gets far away from the Sun, so it should be visible in daytime skys most of the time. Just make a note of where it is in relation to the Sun at night, and then look for it at about the same distance away after the sun has risen. I suppose this is easier to do when it rises in the morning just before the Sun, and you can track it throughout the day.

One more comment. If you look through a tube of some kind, it would probably help you to see daylight objects by cutting out a lot of the glare around you and letting you focus your eye on a small area. But I think this would only work with objects that are already visible. It wouldn't let you see anything not already bright enough to cut through the blue background on it's own.

beskeptical
2002-May-13, 06:09 AM
On 2002-05-12 23:13, David Hall wrote:
I've seen several partial eclipses (78% once) and one annular eclipse,...


Oh, I know this is in the wrong thread but I had to share my eclipse story. When I think about it, well... , talking helps. /phpBB/images/smiles/icon_frown.gif

When I was a child, my parents were afraid the eclipse would blind us so they took us to the movies and we missed it, (Calif.)./phpBB/images/smiles/icon_frown.gif When the next full eclipse occurred in the US, I was in Australia. /phpBB/images/smiles/icon_frown.gif Then, I went to Mexico to see the '91 great eclipse. It was sunny until MINUTES before the event. The cloud cover moved in from land toward the sea. I ran. I staid ahead of the clouds until I got as far out on a little penninsula as you could without swimming. The clouds caught up, the sky dimmed, it was over. I'm jinxed!!! /phpBB/images/smiles/icon_frown.gif /phpBB/images/smiles/icon_frown.gif

But I will be back! I will try again!! I will triumph one day!!! /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_biggrin.gif

Thankyou for listening, I feel better now. /phpBB/images/smiles/icon_smile.gif

<font size=-1>[ This Message was edited by: beskeptical on 2002-05-13 02:18 ]</font>

<font size=-1>[ This Message was edited by: beskeptical on 2002-05-13 02:20 ]</font>

MHS
2002-May-13, 11:55 AM
My story is the opposite of yours! I went to France to see the '99 total eclipse. It was cloudy all day, but just before totality there was a strip of blue in which the eclipse occured. Less than 5 seconds after totality it started to rain, but we'd seen in all! It was really weird; we were on a campsite with lots of other people and during the two minutes of totality people started to scream! And the darkness that occurs is really strange to: it looks like it's totally dark, but you can still see really sharp shadows... spooky. Also bats came flying out of their holes.

I wanna see it again /phpBB/images/smiles/icon_smile.gif.

chris l.
2002-May-13, 05:48 PM
During the annular solar eclipse of 1994, Venus was visible. I had the pleasure of showing this to many high school students. Everyone was amazed. It made very clear the notion that Venus always stays 'close to the sun.'

beskeptical
2002-May-14, 09:44 AM
MHS I am so jealous! Actually, your story sounds great. I looked into going to Turkey (I think that was '00), but decided not to. We would have been there during the big quake, so I guess I was lucky. In '91, it got dim enough for the town lights to come on like it was night. It wasn't as dark as night, but it was as dark as a Mt. St. Helens ash cloud. Definitely eerie.

And, I know this is still the wrong thread, but now I have to share happy thoughts. My son and I have gone south to see the Leonids for 3 of the last 4 years. And for those trips, we had absolutely clear high desert skies. '98 and '01 were just fantastic. We are going to go one more time next Nov. then wait another 33 years. /phpBB/images/smiles/icon_biggrin.gif

<font size=-1>[ This Message was edited by: beskeptical on 2002-05-16 02:44 ]</font>

Kaptain K
2002-May-14, 10:46 AM
beskeptical,
You said,"We are going to go one more time next Nov. then wait another 33 years."
I may be wrong on this (if I am, somebody please correct me), but I remember reading a few years ago (before the current series of Leonid storms) that this may be the last of the storms. According to the article I read, the stream is drifting away from the Earth's orbit and by 2033, they will no longer intersect.
As I said, I hope I am wrong.

beskeptical
2002-May-15, 06:15 AM
Reply to Kaptain K:

You are correct, I didn't want to go on and on. I get carried away with subjects that fascinate me and meteor showers are fascinating.

There have been a couple of astronomers with slightly different predictions on the Leonids peaks since 1998. Based on past events they mapped out the dust stream Earth passes through. For all 4 years their predictions were reliable. That's why we skipped 2000.

2002 is the last year for any great activity. Normally it would recur in 33 years. But, Jupiter is supposed to disturb the dust stream's orbit as you say. It's too far off for me to worry about.

There are some good web sites devoted to the Leonid storms entirely. Easy to brouse with a simple search to find them. Sky and Telescope has a meteor page that I think is linked.