Moon transparency: occultations

[AtomPages]

Has anyone discussed so-called sightings of stars or planets appearing in front of the moon's dark limb? While this is not specifically related to the shape of the earth, it is an argument I see FE's regularly use about the moon being transparent.

There are two separate claims I see: first, that there are historical accounts of lunar occultations where the more distant object appeared in front of the moon, as seen in https://www.sacred-texts.com/earth/za/za63.htm, and in the cited work: https://academic.oup.com/mnras/article/20/8/329/1039466

And second, that the Islamic star and crescent seen on flags is originated in these historical sightings. I cannot find a source for this claim, but one social media poster phrases it like this: "This occurrence has been recognized by Islamic cultures, and is shown on many flags as well as coat of arms for Indo-European countries. "

The Zetetic Astronomy site of course dismisses all explanations of such sightings as insufficient, but my first question is, what would be a reasonable explanation for these historical sightings? I can pull out more specific ones if it would help the discussion, but figured I'd start with the one example above.

And the second question is, is there any merit to the claim that the moon and crescent icon derives from these sightings?

 

[Mendel]

Jupiter being bright and then appearing as "a dark object" suggests an afterimage in the eye of the observer.

If Jupiter simply passed in front of the moon, there's no reason for it to darken.

is there any merit to the claim that the moon and crescent icon derives from these sightings?

given that the sybol dates back well over 2000 years and sources are scarce, I doubt it

I expect star and moon started out separate, until someone tried to mint coins with the symbol

 

[FatPhil]

Has anyone discussed so-called sightings of stars or planets appearing in front of the moon's dark limb? While this is not specifically related to the shape of the earth, it is an argument I see FE's regularly use about the moon being transparent.

There are two separate claims I see: first, that there are historical accounts of lunar occultations where the more distant object appeared in front of the moon, as seen in https://www.sacred-texts.com/earth/za/za63.htm

Please identify which of the many pages of claims is the one you are referring to. The first thing on that page is him referring to being able to see the sun during an annular eclipse:

Given the data/images at http://astro.ukho.gov.uk/eclipse/0331520/ I'm not sure where he would have to be to see that eclipse at 10am, unless he was somewhere in the Sargasso sea - and not sure what time-keeping device he would have had in order to be so precise. New England saw the eclipse at 8am local time (http://astro.ukho.gov.uk/eclipse/0331520/Albany_NY_United_States_1520Oct11.png - "13:10 UT") , Ghana saw it way later (http://astro.ukho.gov.uk/eclipse/0331520/Accra_Ghana_1520Oct11.png - "16:21 UT"). So it had to be somewhere in between. Do we trust the diarist?

To be honest, Zetetic Astronomy is classic loonie-tunes claims without hard corroborated evidence - my best guess is that they simply stared at the sun too long.

 

[AtomPages]

Please identify which of the many pages of claims is the one you are referring to.

The other one that jumped out at me was this one, which is apparently one of the most-quoted ones from FE's:

"On the 15th of March, 1848, when the moon was seven and a half days old, I never saw her unillumined disc so beautifully. . . . On my first looking into the telescope a star of about the 7th magnitude was some minutes of a degree distant from the moon's dark limb. I saw that its occultation by the moon was inevitable. . . . The star, instead of disappearing the moment the moon's edge came in contact with it, apparently glided on the moon's dark face, as if it had been seen through a transparent moon; or, as if a star were between me and the moon. . . ."
Sir James South, of the Royal Observatory, Kensington, in a letter in the "Times" newspaper of April 7, 1848.

I'm having a hard time finding the actual newspaper article.

 

[Ann K]

The only objects likely to come between earth and the moon are satellite debris (today, but certainly not in the past), meteorites (which vanish quickly), or birds/bats. An afterimage, especially strong when the viewer has been staring at the bright object for some time, seems the most likely explanation.

I've often thought that afterimages are the cause of most sightings of "ghosts". Is there any interest in my starting another thread on the subject?

 

[FatPhil]

The other one that jumped out at me was this one, which is apparently one of the most-quoted ones from FE's:

"On the 15th of March, 1848, when the moon was seven and a half days old, I never saw her unillumined disc so beautifully. . . . On my first looking into the telescope a star of about the 7th magnitude was some minutes of a degree distant from the moon's dark limb. I saw that its occultation by the moon was inevitable. . . . The star, instead of disappearing the moment the moon's edge came in contact with it, apparently glided on the moon's dark face, as if it had been seen through a transparent moon; or, as if a star were between me and the moon. . . ."
Sir James South, of the Royal Observatory, Kensington, in a letter in the "Times" newspaper of April 7, 1848.

I'm having a hard time finding the actual newspaper article.

That year and location implies the telescope shouldn't be a crummy one, so it shouldn't be an optical aberration, and that date implies it's not an meteor from one of the well-known showers - it still could be an isolated one of course. This does make it an interesting case.

However, he calls it a "star", but makes no attempt to identify it - this us unusual, suspicious, perhaps. By that time, /Histoire céleste française/ was well established (https://en.wikipedia.org/wiki/Histoire_céleste_française):

Jérôme Lalande published the Histoire céleste française in 1801, which contained an extensive star catalog, among other things. The observations made were made from the Paris Observatory and so it describes mostly northern stars. This catalogue contained the positions and magnitudes of 47,390 stars, out to magnitude 9, and was the most complete catalogue up to that time. A significant reworking of this catalogue by followers of Lalande in 1846 added reference numbers to the stars that are used to refer to some of these stars to this day. The decent accuracy of this catalogue kept it in common use as a reference by observatories around the world throughout the 19th century.

-- https://en.wikipedia.org/wiki/Star_catalogue#Full-sky_catalogues_(in_chronological_order)
Likewise, he says that "it glided". Stars don't do that - they're fixed on the celestial dome. The moon may have slid behind it, but it gliding implies it's moving relative to the heavens, and not a star. A strange choice of words which again makes me think that he didn't think it was actually a star. He was no slouch, he knew how stars behave.

What time of night was this - what's his favourite tipple? (By which I simply imply that observer error can occur, for various reasons, even if the observer is an expert.)

 

[Ann K]

Likewise, he says that "it glided". Stars don't do that

He describes its expected occultation "by the moon" and the moon's edge coming "in contact with it", so it is clear that the moon was doing the gliding. But if he describes the star as gliding, that's another indication that it was an afterimage. If the image is off center and the viewer tries to look at it, it will appear to keep moving as the eye tries ...and fails... to keep up with it.

 

[Landru]

He describes its expected occultation "by the moon" and the moon's edge coming "in contact with it", so it is clear that the moon was doing the gliding. But if he describes the star as gliding, that's another indication that it was an afterimage. If the image is off center and the viewer tries to look at it, it will appear to keep moving as the eye tries ...and fails... to keep up with it.

If you are going to requote it is helpful to include the whole quote and not paraphrase.

 

[Ravi]

The only objects likely to come between earth and the moon are satellite debris (today, but certainly not in the past), meteorites (which vanish quickly), or birds/bats.

You forgetting near Earth asteroids.

 

[FatPhil]

He describes its expected occultation "by the moon" and the moon's edge coming "in contact with it", so it is clear that the moon was doing the gliding. But if he describes the star as gliding, that's another indication that it was an afterimage. If the image is off center and the viewer tries to look at it, it will appear to keep moving as the eye tries ...and fails... to keep up with it.

"The star, instead of disappearing the moment the moon's edge came in contact with it, apparently glided on the moon's dark face"
Removing the subordinate clause becomes: "The star apparently glided on the moon's dark face"

I stand by my interpretation. Yes, he's giving a mixed message, but that's kinda my point. I would have hoped for more precision from someone of his estimable reputation. Then again, perhaps he writes scientific reports in a different voice to that in which he writes letters to newspapers.

 

[deirdre]

I'm having a hard time finding the actual newspaper article.

i dont know about an article but this astromoner 1859 investigating the claims has the date as 1845

https://articles.adsabs.harvard.edu//full/1860MmRAS..28..173A/0000179.000.html

add: he seems to be saying (the edge of the moon is not the egge of the moon because of how light "flares"...these are my words)
page 185

add: ast nachr seens to be

 

[deirdre]

I'm having a hard time finding the actual newspaper article.

i dont know if it was reprinted 3 years later in the Times, but i could only find it in "The Sun" April 21, 1945 .

i did save the column text following and pdf'd the previous part of the article (and the end...i think i snagged it all) if anyone wants the full text, but basically James is just talking about some new telescope. it's probably painfully detailed. you can sign up to the archive with no credit card to view 3 articles free. meaning you can click my link and read it in full if you register. use a real email though as you have to verify.

"the enormous telescope lately constructed by Lord Rosse, and from the extraordinary powers of which great discoveries have been anticipated"

On the 15th of March, when the moon was seven days and a-half old, I never saw her unillumined disk so beautifully nor her mountains so temptingly measurable. On my first looking into the telescope, a star of about the 7th magnitude was some minutes of a degree distant from the moon's dark limb. Seeing that its occultation by the moon was inevitable, as it was the first occultation which had been observed with that telescope, I was anxious that it should be observed by its noble maker ; and very much do I regret that through kindness towards me he would not accede to my wish; for the star, instead of disappealing the moment the moon's edge came in contact with it, apparently glided on the moon's dark face, as if it had been seen through a transparent moon, or as if the stars were between me and the moon. It remained on the moon's disk nearly two seconds of time, and then instantly disappeared, at 10h. 9m. 59.725. sidereal time. I have seen this apparent projection of a star on the moon's face several times, but from the great brilliancy of the star this was the most beautiful I ever saw. The cause of this phenomenon is involved in impenetrable mystery. The only telescopes in point of size comparable with Lord Rosse's 3 feet and 6 feet, are Sir William Herschel's 20 feet and 40 feet Lemaireen's.

https://www.britishnewspaperarchive.co.uk/viewer/bl/0002194/18450421/062/0008

search results:

adding pdf of the above quoted section, you have a scroll down a tad on the pdf

 

[JMartJr]

Jupiter simply passed in front of the moon, there's no reason for it to darken.

Confirmed by looking for pics of ISS crossing moon, found a couple where the station is illuminated, and it indeed does remain bright with the moon behind it.

 

[Mendel]

It remained on the moon's disk nearly two seconds of time, and then instantly disappeared

sounds like it could be another optical illusion

I wonder if these observations kept occuring once the age of astronomical photographs was in full swing; if these are common occurrences, someone ought to have pictures of it if it's objectively happening

 

[deirdre]

if these are common occurrences, someone ought to have pictures of it if it's objectively happening

is it happening in this video on the wiki page. it sort of looks like star is on "top" of the moon here, no?
although one wonders why the FEers use such old examples, if its still a common occurrence with modern telescopes.

https://en.wikipedia.org/wiki/Occultation

Article:

21 April 2007

Source: https://en.wikipedia.org/wiki/File:Occultation.ogv

 

[deirdre]

this astronomer is also explaining what he thinks is happening (although i cant understand him)

https://academic.oup.com/mnras/article/39/3/198/1155296

 

[Mendel]

is it happening in this video on the wiki page. it sort of looks like star is on "top" of the moon here, no?

hmm, I'd say it doesn't, but...

the explanation you're quoting says that the bright limb of the moon appears bigger due to atmospheric glare (and maybe lens imperfections/focus).
So does the dark limb (but less so), and obviously the star as well, which is actually a pinprick at the center of its bright light, which is why the star's bright "disk" can seem to overlap the moon disk a little.

 

[JMartJr]

Objects further away than is the moon, being blocked by the moon. For contrast with the ISS passing in front of the moon in post 13 above. Sometimes a picture is worth 1 kiloword.

Venus emerging from behind the moon:

Jupiter partially occluded by moon:

Saturn partially occluded by moon:

 

[Gary C]

In addition to physical imperfections in the optical elements, there are other sources of distortion and unwanted light. One that comes to mind is the flocking or black coating on the inside of the telescope tube. This is intended to absorb stray light not part of the main optical path. If there is an imperfection in this coating, bright objects like the moon or terrestrial sources of light can sometimes introduce bright artifacts in the observers field of view. Unfortunately there is no way to check for this after the fact. Even if details of the instruments are available, flocking is a step in routine maintenance that might not have been though important enough to note for the historical record.

Here is a short video demonstrating one way this is done for context -
Source: https://www.youtube.com/watch?v=FPFZbqbjbP0


Large telescopes also subject to uneven cooling which could cause the optical path to deviate from its specifications. That could distort the image or result in light hitting the edge of an optical element which might also introduce an unpredictable reflection into the visual field. Again this is a transient phenomenon and not something easy to account for centuries after the fact.

 

[Ravi]

In addition to physical imperfections in the optical elements, there are other sources of distortion and unwanted light. One that comes to mind is the flocking or black coating on the inside of the telescope tube. This is intended to absorb stray light not part of the main optical path. If there is an imperfection in this coating, bright objects like the moon or terrestrial sources of light can sometimes introduce bright artifacts in the observers field of view. Unfortunately there is no way to check for this after the fact. Even if details of the instruments are available, flocking is a step in routine maintenance that might not have been though important enough to note for the historical record.

Large telescopes also subject to uneven cooling which could cause the optical path to deviate from its specifications. That could distort the image or result in light hitting the edge of an optical element which might also introduce an unpredictable reflection into the visual field. Again this is a transient phenomenon and not something easy to account for centuries after the fact.

Straylight is indeed not part of the main optical path, but it does make the image more "hazy". This lowers the contrast of the image and also the dynamic range of course is reduced.
I don't agree the lack of contrast would have been the cause of the effect though. The diffractive telescopes they used were pretty good, but the lenses were far from perfect. The polishing we can achieve today is far from what they could do back then. Also most likely the telescope's main (front) lens and objectives were not achromatised (not yet invented), which means the imaging was not perfectly "sharp".
So these effects make the bright objects "bloom" (appearing bigger than in reality).

 

[AmberRobot]

Straylight is indeed not part of the main optical path, but it does make the image more "hazy". This lowers the contrast of the image and also the dynamic range of course is reduced.
I don't agree the lack of contrast would have been the cause of the effect though. The diffractive telescopes they used were pretty good, but the lenses were far from perfect. The polishing we can achieve today is far from what they could do back then. Also most likely the telescope's main (front) lens and objectives were not achromatised (not yet invented), which means the imaging was not perfectly "sharp".
So these effects make the bright objects "bloom" (appearing bigger than in reality).

For me, the word "bloom" implies a spreading of signal to nearby pixels when an object is causing saturation in a detector. This is not due to image quality or stray light but from the overbrightness of the source.

Perhaps you mean something else but that's what the technical meaning of the word is with regards to sensor effects in imaging.

In CCD images like you may see in a lot of professional astronomical images, the charge can flow more easily along columns and you tend to get vertical streaks above and below a bright, saturated star for instance. I personally have less familiarity with CMOS detectors, which are more common in your typical DSLR, but my understanding is that they are less sensitive to blooming and also wouldn't have the vertical streaks.

 

[Mendel]

Perhaps you mean something else but that's what the technical meaning of the word is with regards to sensor effects in imaging.

wrt film, it includes the lens

Article:

What is Bloom

The Bloom term is commonly used to define the combined effect of bright light dispersion on the boundaries of contrasting image areas, which originates in the optical system, and then is distorted and amplified in the multiple layers of the photographic emulsion.

Bloom physical principles

The Bloom effect is caused by imperfections in optical design. It is most evident in old lenses with poorly coated glass. Inside these lenses, parasitic illumination occurs and then is scattered further in the film emulsion layers. As a result, diffuse glow appears around light sources, bright areas of the scene and along high-contrast edges.

Source: https://blog.dehancer.com/articles/bloom-what-it-is-and-how-it-works/

 

[AmberRobot]

wrt film, it includes the lens

Article:

What is Bloom

The Bloom term is commonly used to define the combined effect of bright light dispersion on the boundaries of contrasting image areas, which originates in the optical system, and then is distorted and amplified in the multiple layers of the photographic emulsion.

Bloom physical principles

The Bloom effect is caused by imperfections in optical design. It is most evident in old lenses with poorly coated glass. Inside these lenses, parasitic illumination occurs and then is scattered further in the film emulsion layers. As a result, diffuse glow appears around light sources, bright areas of the scene and along high-contrast edges.

View attachment 61947

Source: https://blog.dehancer.com/articles/bloom-what-it-is-and-how-it-works/

Fair enough. If you're still using film more power to you!