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Old 02-08-2019, 06:48 PM
Hatchie Hatchie is offline
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Solar eclipse: what's wrong with this picture?

The Eclipse of the Sun in Venice, July 6 1842 by Ippolito Caffi

I look at this painting and instantly know it's not how a real solar eclipse would look (although if it did, it would be spectacular). But I'm at a loss to say why.

I am clearly not well versed in optics. I presume it has something to do with the fact that the sun is millions of miles away, and the rays reaching us are more or less parallel. But then again, you've seen sunbeams breaking through a hole in the clouds. Why does that differ?
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Old 02-08-2019, 07:17 PM
Francis Vaughan Francis Vaughan is online now
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You are correct. Not only is the sun essentially an infinite distance, so is the moon. The image is drawn as if the source of light is only a few miles high. To get the effect of sun's rays breaking through clouds at a wide range of angles you need another cloud higher up that is illuminated by the sun, and it is that cloud that becomes the local source of light.

The painting is depicting a partial phase - one that isn't actually all that spectacular, indeed it only looks as if the sun is rather dim, right up until the last few seconds before totality when the moon's shadow does indeed travel across the land - at a rather high speed - and you are then immersed in full shadow and the really spectacular view of the sun is to be had. From the perspective of any human on the surface the moon's shadow is a straight line. To see it as the edge of a circle you would need to be in space with a very wide view. (For instance we can just make out the circular shape of the Earth's shadow on the moon during a lunar eclipse when we view it from Earth.)
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Old 02-08-2019, 07:23 PM
DPRK DPRK is offline
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The obvious thing wrong is that the sun is not fully eclipsed, yet it's (sort of) dark! The weird wedge of light is also pretty random; it's clearly not a sunbeam.
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Old 02-08-2019, 07:27 PM
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Quartz Quartz is offline
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Because it looks nothing like a real solar eclipse. You would never see that division in the sky.

First off, let's get the obligatory warning out of the way: DO NOT LOOK AT THE SUN UNPROTECTED EXCEPT DURING TOTALITY.

During a real total solar eclipse it very gradually gets darker and darker as more and more of the sun is obscured. But you won't notice until the sun is 90%+ covered. Maybe 95%+. Because the sun is an awesomely powerful source and our eyes adapt. Then you will get Baily's Beads and the Diamond Ring effect. The switch from near-daylight to darkness is very quick. And when the eclipse is no longer total it switches back to full daylight very quickly too. The sun is that powerful a light source. At no point can you on the ground see a division in the sky.

Now, if you are at a distance, say looking from the ISS, then you will be able to see the path the eclipse takes and you will note that the edge of the eclipsed area is curved, not as seen in the painting.

Now, experiencing a total eclipse should be on your bucket list. It's an awesome experience.
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Old 02-09-2019, 02:05 AM
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panache45 panache45 is offline
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I've seen four total solar eclipses, and none looked anything like that painting. It would be impossible, taking into account what a solar eclipse actually is.

But as an artist, I have to defend the idea that a painting doesn't have to be a mirror of reality. That artist had a unique interpretation of the event, and as a work of art rather than science, it's perfectly valid... although I'm not sure exactly what he was saying.
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Old 02-09-2019, 02:38 AM
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Half Man Half Wit Half Man Half Wit is online now
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Quote:
Originally Posted by Francis Vaughan View Post
You are correct. Not only is the sun essentially an infinite distance, so is the moon. The image is drawn as if the source of light is only a few miles high. To get the effect of sun's rays breaking through clouds at a wide range of angles you need another cloud higher up that is illuminated by the sun, and it is that cloud that becomes the local source of light.
The reason that beams of sunlight seem to converge when breaking though the clouds is simply vanishing point perspective---same as with train tracks receding in the distance.
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Old 02-09-2019, 02:58 AM
Francis Vaughan Francis Vaughan is online now
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Originally Posted by Half Man Half Wit View Post
The reason that beams of sunlight seem to converge when breaking though the clouds is simply vanishing point perspective---same as with train tracks receding in the distance.
Ugh, of course!
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Old 02-09-2019, 10:07 AM
DesertDog DesertDog is offline
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Sort of like SciManDan's debunking of this moron's proof that the fact Polaris doesn't move demonstrates that the Earth is flat.
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Old 02-09-2019, 10:19 AM
eburacum45 eburacum45 is offline
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Originally Posted by panache45 View Post
I've seen four total solar eclipses, and none looked anything like that painting. It would be impossible, taking into account what a solar eclipse actually is.
I've only seen one, and it was cloudy. But towards the end there was a time where the shadow of the Moon could be seen, vaguely moving across the clouds. This was a very diffuse effect, and difficult to see, but I wonder whether the artist in this case saw something similar, and has tried to depict the shadow effect in a clear sky.
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Old 02-09-2019, 10:28 AM
pulykamell pulykamell is online now
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Originally Posted by eburacum45 View Post
I've only seen one, and it was cloudy. But towards the end there was a time where the shadow of the Moon could be seen, vaguely moving across the clouds. This was a very diffuse effect, and difficult to see, but I wonder whether the artist in this case saw something similar, and has tried to depict the shadow effect in a clear sky.
My guess was that the artist, assuming they witnessed an actual solar eclipse, was trying to recreate that brief flash of light you get called "the diamond ring effect" as the moon completely covers the sun. You can find many examples of it on Youtube. If somebody is going by memory, that can very well be what the mind remembered.
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Old 02-09-2019, 05:02 PM
bonzer bonzer is offline
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Then you will get Baily's Beads and the Diamond Ring effect.
Baily himself gave a detailed account of observing this particular eclipse from Pavia. Though it was an earlier occasion that had prompted him to note "Baily's Beads" for the first time.
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Old 02-09-2019, 05:55 PM
brossa brossa is offline
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The rays of light illuminating just part of the sky is a dramatic effect, but not realistic. Once you can see that sliver of sun peeking out, you are already being illuminated by it, so you wouldn't see a bright crescent of sun while standing in darkness. Once the Sun is exposed, the whole sky lights up (although at only a percentage of full output) rather than just a segment.
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