APOD: Mars at the Moon's Edge (2020 Aug 15)

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APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by APOD Robot » Sat Aug 15, 2020 4:05 am

Image Mars at the Moon's Edge

Explanation: Does the Moon ever block out Mars? Yes, the Moon occasionally moves in front of all of the Solar System's planets. Just this past Sunday, as visible from some locations in South America, a waning gibbous Moon eclipsed Mars. The featured image from Córdoba, Argentina captured this occultation well, showing a familiar cratered Moon in the foreground with the bright planet Mars unusually adjacent. Within a few seconds, Mars then disappeared behind the Moon, only to reappear a few minutes later across the Moon. Today the Moon moves close to, but not in front of, Venus. Because alignments will not have changed by much, the next two times the Moon passes through this part of the sky – in early September and early October – it will also occult Mars, as seen from parts of South America.

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Ann » Sat Aug 15, 2020 5:15 am

Nice color contrast between the Moon and Mars.

The surface brightness of Mars seems to be every bit as high as the surface brightness of the Moon, even though Mars is about one and a half times as far away from the Sun as the Moon is.

The Moon is a dark body. I know I've read that the Moon is as dark as if it had been paved all over with asphalt.

Ann
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by orin stepanek » Sat Aug 15, 2020 10:39 am

MoonOverMars_Scauso_960.jpg

Beautiful work Sergio! 8-)
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by XgeoX » Sat Aug 15, 2020 11:40 am

Ann wrote:
Sat Aug 15, 2020 5:15 am
Nice color contrast between the Moon and Mars.

The surface brightness of Mars seems to be every bit as high as the surface brightness of the Moon, even though Mars is about one and a half times as far away from the Sun as the Moon is.

The Moon is a dark body. I know I've read that the Moon is as dark as if it had been paved all over with asphalt.

Ann
Hi Ann!
Remember though that Mars right now is about 213 times further away from Earth than the Moon but most importantly I am sure the photographer had to manipulate the exposure in post to get such a beautiful shot. Either that and/or he took several exposures with the camera.

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by De58te » Sat Aug 15, 2020 11:57 am

Maybe a real scientist can confirm this but I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise. I just got the thought that with all the bad luck space exploration has been having exploring the planet Mars, that wouldn't it be ironic that just when Mars disappeared behind the Moon is just when a living Martian creature walked in front of the camera of one of the Martian rovers! And allowing for the speed of light, that radio signal beaming that historic image to Earth has been forever lost! Thanks to the Moon.

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by neufer » Sat Aug 15, 2020 12:57 pm

De58te wrote:
Sat Aug 15, 2020 11:57 am

I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise. I just got the thought that with all the bad luck space exploration has been having exploring the planet Mars, that wouldn't it be ironic that just when Mars disappeared behind the Moon is just when a living Martian creature walked in front of the camera of one of the Martian rovers! And allowing for the speed of light, that radio signal beaming that historic image to Earth has been forever lost! Thanks to the Moon.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Chris Peterson » Sat Aug 15, 2020 1:39 pm

De58te wrote:
Sat Aug 15, 2020 11:57 am
Maybe a real scientist can confirm this but I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise. I just got the thought that with all the bad luck space exploration has been having exploring the planet Mars, that wouldn't it be ironic that just when Mars disappeared behind the Moon is just when a living Martian creature walked in front of the camera of one of the Martian rovers! And allowing for the speed of light, that radio signal beaming that historic image to Earth has been forever lost! Thanks to the Moon.
Don't worry. The data isn't live streamed. It's buffered and sent on command.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Cousin Ricky » Sat Aug 15, 2020 2:59 pm

An alliterative osculation!

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Chris Peterson » Sat Aug 15, 2020 3:01 pm

Cousin Ricky wrote:
Sat Aug 15, 2020 2:59 pm
An alliterative osculation!
Mars Meets the Moon's Margin.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by johnnydeep » Sat Aug 15, 2020 3:14 pm

Chris Peterson wrote:
Sat Aug 15, 2020 3:01 pm
Cousin Ricky wrote:
Sat Aug 15, 2020 2:59 pm
An alliterative osculation!
Mars Meets the Moon's Margin.
Yes - nice!

Also, Minuscule Mars Meets the Mighty Moon's Margin.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Ann » Sat Aug 15, 2020 3:59 pm

XgeoX wrote:
Sat Aug 15, 2020 11:40 am
Ann wrote:
Sat Aug 15, 2020 5:15 am
Nice color contrast between the Moon and Mars.

The surface brightness of Mars seems to be every bit as high as the surface brightness of the Moon, even though Mars is about one and a half times as far away from the Sun as the Moon is.

The Moon is a dark body. I know I've read that the Moon is as dark as if it had been paved all over with asphalt.

Ann
Hi Ann!
Remember though that Mars right now is about 213 times further away from Earth than the Moon but most importantly I am sure the photographer had to manipulate the exposure in post to get such a beautiful shot. Either that and/or he took several exposures with the camera.

Eric
Absolutely!

But remember that what matters in this question is how far away the Moon and Mars are from the Sun.

Ann
Last edited by Ann on Sat Aug 15, 2020 4:16 pm, edited 1 time in total.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by neufer » Sat Aug 15, 2020 4:03 pm

johnnydeep wrote:
Sat Aug 15, 2020 3:14 pm
Chris Peterson wrote:
Sat Aug 15, 2020 3:01 pm
Cousin Ricky wrote:
Sat Aug 15, 2020 2:59 pm

An alliterative osculation!
Mars Meets the Moon's Margin.
Also, Minuscule Mars Meets the Mighty Moon's Margin.
  • Ford circles and Farey sequences :arrow:
https://en.wikipedia.org/wiki/Farey_sequence wrote:
<<There is a connection between Ford circles and Farey sequences. In mathematics, the Farey sequence of order n is the sequence of completely reduced fractions, either between 0 and 1, or without this restriction,[a] which when in lowest terms have denominators less than or equal to n, arranged in order of increasing size. With the restricted definition, each Farey sequence starts with the value 0, denoted by the fraction 0/1, and ends with the value 1, denoted by the fraction 1/1 (although some authors omit these terms).>>
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Fred the Cat » Sat Aug 15, 2020 5:42 pm

In composite images, why don’t they make distant objects in focus sometimes but not in others :?:

I saw this conjunction the other morning but it is very difficult for me to take photos of bright and dim objects together. This morning's conjunction with Venus and the crescent moon would have been a much easier target for an amateur but I decided to go back to bed. :wink:
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Chris Peterson » Sat Aug 15, 2020 5:50 pm

Fred the Cat wrote:
Sat Aug 15, 2020 5:42 pm
In composite images, why don’t they make distant objects in focus sometimes but not in others :?:
The focus is the same. The background shows the limitations of camera optics with point sources, as well as some motion blur because of the long exposure necessary to capture the sky.
I saw this conjunction the other morning but it is very difficult for me to take photos of bright and dim objects together. This morning's conjunction with Venus and the crescent moon would have been a much easier target for an amateur but I decided to go back to bed. :wink:
You need to have good enough optics that the scatter from the bright object doesn't interfere with the nearby dim one. And you need to take the images at different exposures and utilize careful processing to combine them.

I didn't try to image this morning's conjunction, but my allsky camera picked it up along with a meteor. And it's easy to see Venus today naked eye in daylight if you use the Moon as a guide.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by BillBixby » Sat Aug 15, 2020 6:29 pm

Ann wrote:
Sat Aug 15, 2020 3:59 pm
XgeoX wrote:
Sat Aug 15, 2020 11:40 am
Ann wrote:
Sat Aug 15, 2020 5:15 am
Nice color contrast between the Moon and Mars.

The surface brightness of Mars seems to be every bit as high as the surface brightness of the Moon, even though Mars is about one and a half times as far away from the Sun as the Moon is.

The Moon is a dark body. I know I've read that the Moon is as dark as if it had been paved all over with asphalt.

Ann
Hi Ann!
Remember though that Mars right now is about 213 times further away from Earth than the Moon but most importantly I am sure the photographer had to manipulate the exposure in post to get such a beautiful shot. Either that and/or he took several exposures with the camera.

Eric
Absolutely!

But remember that what matters in this question is how far away the Moon and Mars are from the Sun.

Ann
Was this shot taken with a backyard telescope and terrific camera or with images made available from an observatory? Either way, terrific work and picture. Thank you Sergio Scauso. From you link I have taken this information. I hope you don't disapprove.

Was this a 1 shot photo as mars in so much detail, only wondering due to DOF

Reply · Sergio Scauso es el apilado de 75 frames de un vídeo de 5.5"

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Grizzly » Sat Aug 15, 2020 9:20 pm

Can anyone explain why Mars would appear to be gibbous rather than a full disk? What geometry makes that even remotely possible?

heehaw

Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by heehaw » Sat Aug 15, 2020 10:12 pm

De58te wrote:
Sat Aug 15, 2020 11:57 am
I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise.
Quite right! I was on Apollo 17, and the radio guys at the next console were radio astronomers who were WOWED at the radio silence every time we went behind the Moon. (They were probing the moons surface with radio waves).

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Chris Peterson » Sat Aug 15, 2020 11:43 pm

Grizzly wrote:
Sat Aug 15, 2020 9:20 pm
Can anyone explain why Mars would appear to be gibbous rather than a full disk? What geometry makes that even remotely possible?
Mars (and all the outer planets) always appears gibbous, except when it's at opposition (or conjunction, but then it's a daytime object and not very visible).
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by BDanielMayfield » Sat Aug 15, 2020 11:45 pm

heehaw wrote:
Sat Aug 15, 2020 10:12 pm
De58te wrote:
Sat Aug 15, 2020 11:57 am
I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise.
Quite right! I was on Apollo 17, and the radio guys at the next console were radio astronomers who were WOWED at the radio silence every time we went behind the Moon. (They were probing the moons surface with radio waves).
The retired professor who modestly calls himself “heehaw” has just dropped a major clue as to his real identity. He worked at NASA’s Houston mission control during part of the Apollo program!
Last edited by BDanielMayfield on Sat Aug 15, 2020 11:58 pm, edited 1 time in total.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by neufer » Sat Aug 15, 2020 11:49 pm

Grizzly wrote:
Sat Aug 15, 2020 9:20 pm

Can anyone explain why Mars would appear to be gibbous rather than a full disk? What geometry makes that even remotely possible?
  • The Earth is near superior elongation as viewed from Mars :?:
https://earthsky.org/sky-archive/smallest-martian-phase-on-september-13 wrote:
Smallest Martian phase on September 13, 2016
by Bruce McClure in Sky Archive | September 13, 2016

<<Tonight – September 13, 2016 – Mars presents its smallest phase of the year toward Earth. Did you know Mars shows phases? It does, though not as noticeably as Venus or Mercury. By a wonderful coincidence, the moon and Mars momentarily display the same phase on September 13. Neat, huh? And perfectly coincidental. Look for tonight’s waxing gibbous moon to provide a very good approximation of Mars’ present phase.>>
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by alter-ego » Sun Aug 16, 2020 2:17 am

neufer wrote:
Sat Aug 15, 2020 11:49 pm
Grizzly wrote:
Sat Aug 15, 2020 9:20 pm

Can anyone explain why Mars would appear to be gibbous rather than a full disk? What geometry makes that even remotely possible?
  • The Earth is near superior elongation as viewed from Mars :?:
I've not heard the word superior tied to elongation before. As viewed from a superior planet, I believe it would simply be Earth is at "greatest elongation".
As viewed from Earth, the condition is called quadrature (Eastern and Western).

Looking at the phase of Mars over 300 years, Mars' minimum phase at quadrature ranges from 84% to 90%.
Generally, the closer Mars is to Earth at quadrature, the smaller the phase, i.e. 84% phase occurs when Earth-Mars distance around ~0.9 to ~1AU
 
Specific Orbital Positions.png
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by neufer » Sun Aug 16, 2020 12:21 pm

alter-ego wrote:
Sun Aug 16, 2020 2:17 am
neufer wrote:
Sat Aug 15, 2020 11:49 pm
Grizzly wrote:
Sat Aug 15, 2020 9:20 pm

Can anyone explain why Mars would appear to be gibbous rather than a full disk? What geometry makes that even remotely possible?
  • The Earth is near superior elongation as viewed from Mars :?:
I've not heard the word superior tied to elongation before.

As viewed from a superior planet, I believe it would simply be Earth is at "greatest elongation".
https://en.wikipedia.org/wiki/Grok wrote:
<<Grok is a neologism coined by American writer Robert A. Heinlein for his 1961 science fiction novel Stranger in a Strange Land. While the Oxford English Dictionary summarizes the meaning of grok as "to understand intuitively or by empathy, to establish rapport with" and "to empathize or communicate sympathetically (with); also, to experience enjoyment", Heinlein's concept is far more nuanced, with critic Istvan Csicsery-Ronay Jr. observing that "the book's major theme can be seen as an extended definition of the term". The concept of grok garnered significant critical scrutiny in the years after the book's initial publication. The term and aspects of the underlying concept have become part of communities as diverse as polyamory (in particular the Church of All Worlds) and computer science.

Critic David E. Wright Sr. points out that in the 1991 "uncut" edition of Stranger, the word grok "was used first without any explicit definition on page 22" and continued to be used without being explicitly defined until page 253 (emphasis in original). He notes that this first intensional definition is simply "to drink", but that this is only a metaphor "much as English 'I see' often means the same as 'I understand'". Critics have bridged this absence of explicit definition by citing passages from Stranger that illustrate the term. A selection of these passages follows:
Grok means "to understand," of course, but Dr. Mahmoud, who might be termed the leading Terran expert on Martians, explains that it also means, "to drink" and "a hundred other English words, words which we think of as antithetical concepts. 'Grok' means all of these. It means 'fear,' it means 'love,' it means 'hate'—proper hate, for by the Martian 'map' you cannot hate anything unless you grok it, understand it so thoroughly that you merge with it and it merges with you—then you can hate it. By hating yourself. But this implies that you love it, too, and cherish it and would not have it otherwise. Then you can hate—and (I think) Martian hate is an emotion so black that the nearest human equivalent could only be called mild distaste.

'Grok' means 'identically equal.' The human cliché 'This hurts me worse than it does you' has a distinctly Martian flavor. The Martian seems to know instinctively what we learned painfully from modern physics, that observer acts with observed through the process of observation. 'Grok' means to understand so thoroughly that the observer becomes a part of the observed—to merge, blend, intermarry, lose identity in group experience. It means almost everything that we mean by religion, philosophy, and science and it means as little to us as color does to a blind man."

The Martian Race had encountered the people of the fifth planet, grokked them completely, and had taken action; asteroid ruins were all that remained, save that the Martians continued to praise and cherish the people they had destroyed."

All that groks is God."
Robert A. Heinlein originally coined the term grok in his 1961 novel Stranger in a Strange Land as a Martian word that could not be defined in Earthling terms, but can be associated with various literal meanings such as "water", "to drink", "life", or "to live", and had a much more profound figurative meaning that is hard for terrestrial culture to understand because of its assumption of a singular reality.

According to the book, drinking water is a central focus on Mars, where it is scarce. Martians use the merging of their bodies with water as a simple example or symbol of how two entities can combine to create a new reality greater than the sum of its parts. The water becomes part of the drinker, and the drinker part of the water. Both grok each other. Things that once had separate realities become entangled in the same experiences, goals, history, and purpose. Within the book, the statement of divine immanence verbalized between the main characters, "Thou Art God", is logically derived from the concept inherent in the term grok.

Heinlein describes Martian words as "guttural" and "jarring". Martian speech is described as sounding "like a bullfrog fighting a cat". Accordingly, grok is generally pronounced as a guttural gr terminated by a sharp k with very little or no vowel sound.>>
alter-ego wrote:
Sun Aug 16, 2020 2:17 am



As viewed from Earth, the condition is called quadrature (Eastern and Western).

Looking at the phase of Mars over 300 years, Mars' minimum phase at quadrature ranges from 84% to 90%.
Generally, the closer Mars is to Earth at quadrature, the smaller the phase, i.e. 84% phase occurs when Earth-Mars distance around ~0.9 to ~1AU
Mars' minimum phase occurs when the Earth is near "greatest elongation" as viewed from Mars.

Considering Mars' elliptical orbit Mars may or may not be at quadrature as viewed from Earth at such times.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by XgeoX » Sun Aug 16, 2020 12:31 pm

Ann wrote:
Sat Aug 15, 2020 3:59 pm
XgeoX wrote:
Sat Aug 15, 2020 11:40 am
Ann wrote:
Sat Aug 15, 2020 5:15 am
Nice color contrast between the Moon and Mars.

The surface brightness of Mars seems to be every bit as high as the surface brightness of the Moon, even though Mars is about one and a half times as far away from the Sun as the Moon is.

The Moon is a dark body. I know I've read that the Moon is as dark as if it had been paved all over with asphalt.

Ann
Hi Ann!
Remember though that Mars right now is about 213 times further away from Earth than the Moon but most importantly I am sure the photographer had to manipulate the exposure in post to get such a beautiful shot. Either that and/or he took several exposures with the camera.

Eric
Absolutely!

But remember that what matters in this question is how far away the Moon and Mars are from the Sun.

Ann
My bad Ann!
Mea culpa! :oops:

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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by alter-ego » Mon Aug 17, 2020 12:11 am

neufer wrote:
Sun Aug 16, 2020 12:21 pm
alter-ego wrote:
Sun Aug 16, 2020 2:17 am



As viewed from Earth, the condition is called quadrature (Eastern and Western).

Looking at the phase of Mars over 300 years, Mars' minimum phase at quadrature ranges from 84% to 90%.
Generally, the closer Mars is to Earth at quadrature, the smaller the phase, i.e. 84% phase occurs when Earth-Mars distance around ~0.9 to ~1AU
Mars' minimum phase occurs when the Earth is near "greatest elongation" as viewed from Mars.

Considering Mars' elliptical orbit Mars may or may not be at quadrature as viewed from Earth at such times.
Good points. Unlike circles, lines perpendicular to real orbital tangents do not intersect the Sun most of the time.
Just to clarify, the minimum phases I listed above is accurate. Curious about what the phase error roughly is for 90°quadrature positions, I found there is ~0.04% phase error per degree error from greatest elongation. Over 45 years, I considered phase minima at greatest elongations ranging from 81° to 97°, and the associated phases at the quadrature angle ≡ 90°.
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Re: APOD: Mars at the Moon's Edge (2020 Aug 15)

Post by Mountainjim62 » Tue Aug 18, 2020 3:32 pm

BDanielMayfield wrote:
Sat Aug 15, 2020 11:45 pm
heehaw wrote:
Sat Aug 15, 2020 10:12 pm
De58te wrote:
Sat Aug 15, 2020 11:57 am
I read in science fiction that radio signals cannot travel through the Moon. That is why the far side of the Moon is free from man made cacophony of radio noise.
Quite right! I was on Apollo 17, and the radio guys at the next console were radio astronomers who were WOWED at the radio silence every time we went behind the Moon. (They were probing the moons surface with radio waves).
The retired professor who modestly calls himself “heehaw” has just dropped a major clue as to his real identity. He worked at NASA’s Houston mission control during part of the Apollo program!
Or as he says, he, "was ON Apollo 17" as in "ON"?