APOD: Crescent Moon HDR (2020 Aug 24)

[APOD Robot]

Crescent Moon HDR

Explanation: How come the crescent Moon doesn't look like this? For one reason, because your eyes can't simultaneously discern bright and dark regions like this. Called earthshine or the da Vinci glow, the unlit part of a crescent Moon is visible but usually hard to see because it is much dimmer than the sunlit arc. In our digital age, however, the differences in brightness can be artificially reduced. The featured image is actually a digital composite of 15 short exposures of the bright crescent, and 14 longer exposures of the dim remainder. The origin of the da Vinci glow, as explained by Leonardo da Vinci about 510 years ago, is sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth.

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[Ann]

APOD Robot wrote:

...your eyes can't simultaneously discern bright and dark regions like this.

And the camera can't either, at least not cameras in the past. That's why there are no stars in the black sky over the astronauts on the Moon in Apollo 11 Moon landing photos.

Ann

[JohnD]

The blurb refers to the "da Vinci glow", and gives links to da Vinci, and to previous APODs that show the glow, but nothing to da Vinci's original - geniusly original, for the time, even if erronius! - explanation. It's in the Codex Leicester, a collection of his papers on astronomical and other subjects, that is now owned by Bill Gates, who bought it for $30 MILLION nearly thirty years ago.

da Vinci suggests that as the Earth is covered with water, which reflect sunlight, so must the Moon, whose oceans reflect back the reflected sunlight. It's on a page entitled " "Of the Moon: No Solid Body is Lighter than Air."
See: https://www.aps.org/publications/apsnew ... istory.cfm

John

[orin stepanek]

HdrMoon_Claro_1080.jpg

Stark beautiful simply beautiful!

[johnnydeep]

The blurb refers to the "da Vinci glow", and gives links to da Vinci, and to previous APODs that show the glow, but nothing to da Vinci's original - geniusly original, for the time, even if erronius! - explanation. It's in the Codex Leicester, a collection of his papers on astronomical and other subjects, that is now owned by Bill Gates, who bought it for $30 MILLION nearly thirty years ago.

da Vinci suggests that as the Earth is covered with water, which reflect sunlight, so must the Moon, whose oceans reflect back the reflected sunlight. It's on a page entitled " "Of the Moon: No Solid Body is Lighter than Air."
See: https://www.aps.org/publications/apsnew ... istory.cfm

John

So, are you saying that da Vinci was right about the "sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth" but wrong about what was doing the reflecting?

[DMSF]

Am I the only one to wonder why is the earthshine brighter (in this photo) at the limb than at the center of the Moon's disc?

[Chris Peterson]

Am I the only one to wonder why is the earthshine brighter (in this photo) at the limb than at the center of the Moon's disc?

I wouldn't look too hard at any of the relative intensities. Making an image like this is just about the most difficult HDR processing job there is. The dynamic range is not only huge, but the different areas are not independent, because there is a large amount of atmospheric scatter from the crescent that interferes with the light collected from the shadowed parts.

[DrJoeS]

Ye that is a difficult photo to take and to process. I have shot over a hundred crescent moons from my Florida backyard. The humidity and light scatter make this kind of image impossible. But I do appreciate it and am happy you presented it today.

[JohnD]

The blurb refers to the "da Vinci glow", and gives links to da Vinci, and to previous APODs that show the glow, but nothing to da Vinci's original - geniusly original, for the time, even if erronius! - explanation. It's in the Codex Leicester, a collection of his papers on astronomical and other subjects, that is now owned by Bill Gates, who bought it for $30 MILLION nearly thirty years ago.

da Vinci suggests that as the Earth is covered with water, which reflect sunlight, so must the Moon, whose oceans reflect back the reflected sunlight. It's on a page entitled " "Of the Moon: No Solid Body is Lighter than Air."
See: https://www.aps.org/publications/apsnew ... istory.cfm

John

So, are you saying that da Vinci was right about the "sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth" but wrong about what was doing the reflecting?

Johnny,
It's not just me who thinks he was right. If many, many others did not feel that da Vinci was perfectly correct in his theory of the reason for Moonglow, the phenomenon would not be given his name, would it? He should be forgiven for supposing that the Moon had many seas, whose water reflected the light. There were no telescopes until a century after his time, and Lunar mapping not until two hundred years later, but still the flat areas were named "Mare", seas. Now that we can see the Far Side of the Moon, it has no such flat areas, so we have not perpetuated that mistake in naming Far Side Features, but we have persisted on Mars with the Maris Erythraeum, Sirenum, Cimmerium etc.

My post was to correct an omission (in my view) in the original blurb, that didn't provide a link to da Vinci's original words and diagrams. I would have posted an image of the relevant page, but unlike the inestimable Anne and neufer, I cannot work how to post pictures here.

[johnnydeep]

The blurb refers to the "da Vinci glow", and gives links to da Vinci, and to previous APODs that show the glow, but nothing to da Vinci's original - geniusly original, for the time, even if erronius! - explanation. It's in the Codex Leicester, a collection of his papers on astronomical and other subjects, that is now owned by Bill Gates, who bought it for $30 MILLION nearly thirty years ago.

da Vinci suggests that as the Earth is covered with water, which reflect sunlight, so must the Moon, whose oceans reflect back the reflected sunlight. It's on a page entitled " "Of the Moon: No Solid Body is Lighter than Air."
See: https://www.aps.org/publications/apsnew ... istory.cfm

John

So, are you saying that da Vinci was right about the "sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth" but wrong about what was doing the reflecting?

Johnny,
It's not just me who thinks he was right. If many, many others did not feel that da Vinci was perfectly correct in his theory of the reason for Moonglow, the phenomenon would not be given his name, would it? He should be forgiven for supposing that the Moon had many seas, whose water reflected the light. There were no telescopes until a century after his time, and Lunar mapping not until two hundred years later, but still the flat areas were named "Mare", seas. Now that we can see the Far Side of the Moon, it has no such flat areas, so we have not perpetuated that mistake in naming Far Side Features, but we have persisted on Mars with the Maris Erythraeum, Sirenum, Cimmerium etc.

My post was to correct an omission (in my view) in the original blurb, that didn't provide a link to da Vinci's original words and diagrams. I would have posted an image of the relevant page, but unlike the inestimable Anne and neufer, I cannot work how to post pictures here.

Well, you said he was "geniusly original, for the time, even if erronius" (sic), i.e., wrong, so I thought you were being critical of him. My bad. And yes, he can't be faulted for not having a telescope to look through!

As for posting pics, use the Attachments tab at the bottom to upload a pic from your local device, or use the picture button to embed a pic from a URL.

[JohnD]

Thank you, Johnny!

And now, "Of the Moon: No solid body is lighter than Air"

[mostly cloudy]

This photograph just continues to amaze a day later. It appears suspended on whichever screen I view it. What a superb effort,

[neufer]

<<The Codex Leicester [Lester] is a collection of scientific writings by Leonardo da Vinci. The Codex is named after Thomas Coke, later credited to Earl of Leicester, who purchased it in 1719. The manuscript currently holds the record for the second highest sale price of any book, as it was sold to Bill Gates at Christie's auction house on 11 November 1994 in New York for US$30,802,500 .

The Codex provides an insight into the inquiring mind of the definitive Renaissance artist, scientist and thinker as well as an exceptional illustration of the link between art and science and the creativity of the scientific process.

The notebook is leather-bound and consists of 36 sheets of size 29 × 22 cm. The manuscript does not take the form of a single linear script, but is rather a mixture of Leonardo's observations and theories on astronomy; the properties of water, rocks, and fossils; air, and celestial light. The topics addressed include:

• An explanation of why fossils of sea creatures can be found on mountains. Hundreds of years before plate tectonics became accepted scientific theory, Leonardo believed that mountains had previously formed sea beds, which were gradually lifted until they formed mountains.
  
  The movement of water. This is the main topic of the Leicester Codex. Among other things, Leonardo wrote about the flow of water in rivers, and how it is affected by different obstacles put in its way. From his observations he made recommendations about bridge construction and erosion.
  
  The luminosity of the Moon. Leonardo speculated that the Moon's surface is covered by water, which reflects light from the Sun. In this model, waves on the water's surface cause the light to be reflected in many directions, explaining why the Moon is not as bright as the Sun. Leonardo explained that the pale glow on the dark portion of the crescent Moon is caused by sunlight reflected from the Earth. Thus, he described the phenomenon of planetshine one hundred years before the German astronomer Johannes Kepler proved it.

The Codex consists of 18 sheets of paper, each folded in half and written on both sides, forming the complete 72-page document. At one time the sheets were bound together, but they are now displayed separately. It was handwritten in Italian by Leonardo, using his characteristic mirror writing, and supported by copious drawings and diagrams.>>

The notes on Leonardo da Vinci's famous Vitruvian Man image.

---

<<Leonardo da Vinci wrote most of his personal notes in mirror, only using standard writing if he intended his texts to be read by others. The purpose of this practice by Leonardo remains unknown, though several possible reasons have been suggested. For example, writing left handed from left to right would have been messy because the ink just put down would smear as his hand moved across it. Writing in reverse would prevent such smudging. An alternative theory is that the process of rotating the linguistic object in memory before setting it to paper, and rotating it before reading it back, is a method of reinforcement learning.

An informal Australian newspaper experiment identified 10 true mirror-writers in a readership of 65,000. A higher proportion of left-handed people are better mirror writers than right-handed people, perhaps because it is more natural for a left-hander to write backwards. 15% of left-handed people have the language centres in both halves of their brain. The cerebral cortex and motor homunculus are affected by this, causing the person to be able to read and write backwards quite naturally.>>

[JohnD]

Strange, I've just had a one of the usual emails, notifying me that there has been a post on this thread, by one "marvini".

But he ain't here!

"The other day upon the stair
I met a man who wasn't there.
He wasn't there again today
I wish, I wish he'd go away!"
(William Hughes Mearns, 1875–1965)

[Ann]

Strange, I've just had a one of the usual emails, notifying me that there has been a post on this thread, by one "marvini".

But he ain't here!

"The other day upon the stair
I met a man who wasn't there.
He wasn't there again today
I wish, I wish he'd go away!"
(William Hughes Mearns, 1875–1965)

Ha-ha! That's one of my favorite poems!

Ann