APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

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APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by APOD Robot » Fri Oct 30, 2020 4:05 am

[img]https://apod.nasa.gov/apod/calendar/S_201030.jpg[/img] Fear and Dread: The Moons of Mars

Explanation: On Halloween fear and dread will stalk your night skies, also known as Phobos and Deimos the moons of Mars. The 2020 opposition of Mars was on October 13, so the Red Planet will still rise shortly after sunset. Near Halloween's Full Moon on the sky, its strange yellowish glow will outshine other stars throughout the night. But the two tiny Martian moons are very faint and in close orbits, making them hard to spot, even with a small telescope. You can find them in this carefully annotated composite view though. The overexposed planet's glare is reduced and orbital paths for inner moon Phobos and outer moon Deimos are overlayed on digitally combined images captured on October 6. The diminutive moons of Mars were discovered in August of 1877 by astronomer Asaph Hall at the US Naval Observatory using the Great Equatorial 26-inch Alvan Clark refractor</a>.

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Fear and Dread of Angeline Stickney

Post by neufer » Fri Oct 30, 2020 1:10 pm

https://en.wikipedia.org/wiki/Asaph_Hall wrote: <<During Mars' closest approach in 1877, Asaph Hall (October 15, 1829 – November 22, 1907) was encouraged by Angeline Stickney, his wife, to search for the Martian moons. His calculations have shown that the orbit should be very close to the planet. Hall wrote "The chance of finding a satellite appeared to be very slight, so that I might have abandoned the search had it not been for the encouragement of my wife."

Asaph Hall discovered Deimos on August 12, 1877 at about 07:48 UTC and Phobos on August 18, 1877, at the US Naval Observatory in Washington, D.C., at about 09:14 GMT. At the time, he was deliberately searching for Martian moons. Hall had previously seen what appeared to be a Martian moon on August 10, but due to bad weather, he could not definitively identify them until later.

Hall recorded his discovery of Phobos in his notebook as follows:
  • "I repeated the examination in the early part of the night of 11th [August 1877], and again found nothing, but trying again some hours later I found a faint object on the following side and a little north of the planet. I had barely time to secure an observation of its position when fog from the River stopped the work. This was at half past two o'clock on the night of the 11th. Cloudy weather intervened for several days.

    "On 15 August the weather looking more promising, I slept at the Observatory. The sky cleared off with a thunderstorm at 11 o'clock and the search was resumed. The atmosphere however was in a very bad condition and Mars was so blazing and unsteady that nothing could be seen of the object, which we now know was at that time so near the planet as to be invisible.

    "On 16 August the object was found again on the following side of the planet, and the observations of that night showed that it was moving with the planet, and if a satellite, was near one of its elongations. Until this time I had said nothing to anyone at the Observatory of my search for a satellite of Mars, but on leaving the observatory after these observations of the 16th, at about three o'clock in the morning, I told my assistant, George Anderson, to whom I had shown the object, that I thought I had discovered a satellite of Mars. I told him also to keep quiet as I did not wish anything said until the matter was beyond doubt. He said nothing, but the thing was too good to keep and I let it out myself. On 17 August between one and two o'clock, while I was reducing my observations, Professor Newcomb came into my room to eat his lunch and I showed him my measures of the faint object near Mars which proved that it was moving with the planet.

    "On 17 August while waiting and watching for the outer moon, the inner one was discovered. The observations of the 17th and 18th put beyond doubt the character of these objects and the discovery was publicly announced by Admiral Rodgers."
Hall retired from the Navy in 1891. He became a lecturer in celestial mechanics at Harvard University in 1896, and continued to teach there until 1901.>>
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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by Chris Peterson » Fri Oct 30, 2020 1:42 pm

APOD Robot wrote:
Fri Oct 30, 2020 4:05 am
The 2020[/url] opposition of Mars was on October 13, so the Red Planet will still rise shortly after sunset.
Post opposition, Mars is now rising well before sunset. And it's bright enough at the moment to see while the Sun is still up, especially with binoculars. Last night it was just above the rising Moon, which made finding it easy just before sunset.
Chris

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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by Isaiah 40:26 » Fri Oct 30, 2020 3:58 pm

The diminutive moons of Mars should be named Happy, Dopey, Grumpy, Sneezy and Sleepy.

AnAPODfan

Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by AnAPODfan » Fri Oct 30, 2020 5:03 pm

Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.

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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by MarkBour » Fri Oct 30, 2020 6:37 pm

AnAPODfan wrote:
Fri Oct 30, 2020 5:03 pm
Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.
Good question. You might email the astrophotographer, Dennis Simmons. The link on the caption has: nardes at optusnet dot com .

I assume that as the night progressed, that's exactly what he got. One image much brighter than the others. I can't think of anything that should have caused it, maybe just variability in Earth's atmosphere during the night?

The markings indicate a Takahashi Mewlon 210mm. That gives me some hope that Phobos can be seen with something less than Asaph Hall's 26-in refractor. But in the APOD caption, RJN has indicated that this is hard to do. And the accounts of Hall's original finding of them also make it sound difficult without a big scope.
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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by Chris Peterson » Fri Oct 30, 2020 6:59 pm

MarkBour wrote:
Fri Oct 30, 2020 6:37 pm
AnAPODfan wrote:
Fri Oct 30, 2020 5:03 pm
Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.
Good question. You might email the astrophotographer, Dennis Simmons. The link on the caption has: nardes at optusnet dot com .

I assume that as the night progressed, that's exactly what he got. One image much brighter than the others. I can't think of anything that should have caused it, maybe just variability in Earth's atmosphere during the night?

The markings indicate a Takahashi Mewlon 210mm. That gives me some hope that Phobos can be seen with something less than Asaph Hall's 26-in refractor. But in the APOD caption, RJN has indicated that this is hard to do. And the accounts of Hall's original finding of them also make it sound difficult without a big scope.
You do not need a big telescope to image the moons of Mars. Indeed, a larger aperture might work against you unless you're using lucking imaging techniques. What you need is clean, high quality optics, because the problem comes from scatter and glare from Mars preventing the moons from showing. With apparent magnitudes of 11 and 12, the moons are easily imaged in small scopes... if you can avoid mag -2.5 Mars (~400,000 times brighter) from interfering.
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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by nardes » Fri Oct 30, 2020 8:21 pm

AnAPODfan wrote:
Fri Oct 30, 2020 5:03 pm
Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.
Hi

The variations in brightness are likely due to capture and processing anomalies as the glare from the diffraction spikes of the Mewlon 210 tended to pollute the Phobos images. Also, depending on which Aligning and Stacking application I used, and what Combine Mode (Mean, Max, Average) I used, I obtained slightly different results.

I have attached a Max Combine stack of the 60 frames, each a 1 sec exposure, taken over a 1 hour period with one exposure every 60 secs, which show the raw orbits of Phobos and Deimos over the 60 mins I was recording. I chose 60 mins as this gave Phobos time to clear the horizontal diffraction spike glare before then being swamped by the glare from the vertical diffraction spike.

I also made a "pretty picture" by using Photoshop Layers to "reveal" the positions of Phobos and Deimos at the start and end of capture, plus mid-point and two points in-between.

Cheers

Dennis
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heehaw

Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by heehaw » Fri Oct 30, 2020 8:43 pm

The Dogon people in Africa knew all about the moons of Mars. Well, of course, maybe. I myself actually VISITED the Dogon people, long ago. They have rejected modern society! (How COULD they!) They are cliff dwellers and my tour guide was a Dogon who ... brace yourself ... had visited Ohio. Please google Dogon. I love those people!

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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by neufer » Fri Oct 30, 2020 10:49 pm

heehaw wrote:
Fri Oct 30, 2020 8:43 pm

The Dogon people in Africa knew all about the moons of Mars. Well, of course, maybe. I myself actually VISITED the Dogon people, long ago. They have rejected modern society! (How COULD they!) They are cliff dwellers and my tour guide was a Dogon who ... brace yourself ... had visited Ohio. Please google Dogon. I love those people!
  • The Laputa people of Lagado knew all about the moons of Mars.

    It is unclear exactly what the Dogon people of Mali knew.
https://en.wikipedia.org/wiki/Lagado wrote:
<<Lagado is a Capital City from the 1726 _Gulliver's Travels_ by Jonathan Swift. On Mars's largest moon, Phobos, there is a planitia, Lagado Planitia, which is named after Swift's Lagado because of his 'prediction' of the two then undiscovered Martian moons, which his Laputan astronomers had discovered.

Lagado is the capital of the nation Balnibarbi, which is ruled by a tyrannical king from a flying island called Laputa. Lagado is on the ground below Laputa, and also has access to Laputa at any given time to proceed in an attack or defense. Lagado is poverty stricken like the rest of the nation. The king had invested a great fortune on building an Academy of Projectors in Lagado so that it shall contribute to the nation's development through research, but so far the Academy has yielded no result. The author has vividly described bizarre and seemingly pointless experiments conducted there, for example - trying to change human excretion back into food and trying to extract sunbeams out of cucumbers or teaching mathematics to pupils by writing propositions on wafers and consuming them with "cephalick tincture". Gulliver is clearly unimpressed with this academy and offers many suggestions to improve it. The Academy is home to The Engine, a fictitious device resembling a modern computer.>>
https://en.wikipedia.org/wiki/Dogon_people wrote:
<<Starting with the French anthropologist Marcel Griaule, several authors have claimed that Dogon traditional religion incorporates details about extrasolar astronomical bodies that could not have been discerned from naked-eye observation. The idea has entered the New Age and ancient astronaut literature as evidence that extraterrestrial aliens visited Mali in the distant past. Other authors have argued that previous 20th-century European visitors to the Dogon are a far more plausible source of such information and dispute whether Griaule's account accurately describes Dogon myths at all.

From 1931 to 1956, Griaule studied the Dogon in field missions ranging from several days to two months in 1931, 1935, 1937 and 1938 and then annually from 1946 until 1956. In late 1946, Griaule spent a consecutive 33 days in conversations with the Dogon wiseman Ogotemmêli, the source of much of Griaule and Dieterlen's future publications. They reported that the Dogon believe that the brightest star in the night sky, Sirius (sigi tolo or "star of the Sigui"), has two companion stars, pō tolo (the Digitaria star), and ęmmę ya tolo, (the female Sorghum star), respectively the first and second companions of Sirius A. Sirius, in the Dogon system, formed one of the foci for the orbit of a tiny star, the companionate Digitaria star. When Digitaria is closest to Sirius, that star brightens: when it is farthest from Sirius, it gives off a twinkling effect that suggests to the observer several stars. The orbit cycle takes 50 years. They also claimed that the Dogon appeared to know of the rings of Saturn, and the moons of Jupiter.

Griaule and Dieterlen were puzzled by this Sudanese star system, and prefaced their analysis with the disclaimer, "The problem of knowing how, with no instruments at their disposal, men could know the movements and certain characteristics of virtually invisible stars has not been settled, nor even posed."

More recently, doubts have been raised about the validity of Griaule and Dieterlen's work. In a 1991 article in Current Anthropology, anthropologist Wouter van Beek concluded after his research among the Dogon that, "Though they do speak about sigu tolo [which is what Griaule claimed the Dogon called Sirius] they disagree completely with each other as to which star is meant; for some it is an invisible star that should rise to announce the sigu [festival], for another it is Venus that, through a different position, appears as sigu tolo. All agree, however, that they learned about the star from Griaule."

Griaule's daughter Geneviève Calame-Griaule responded in a later issue, arguing that Van Beek did not go "through the appropriate steps for acquiring knowledge" and suggesting that van Beek's Dogon informants may have thought that he had been "sent by the political and administrative authorities to test the Dogon's Muslim orthodoxy".

In a 1978 critique, skeptic Ian Ridpath concluded: "There are any number of channels by which the Dogon could have received Western knowledge long before they were visited by Griaule and Dieterlen." In his book Sirius Matters, Noah Brosch postulates that the Dogon may have had contact with astronomers based in Dogon territory during a five-week expedition, led by Henri-Alexandre Deslandres, to study the solar eclipse of 16 April 1893.

Robert Todd Carroll also states that a more likely source of the knowledge of the Sirius star system is from contemporary, terrestrial sources who provided information to interested members of the tribes. James Oberg, however, citing these suspicions notes their completely speculative nature, writing that, "The obviously advanced astronomical knowledge must have come from somewhere, but is it an ancient bequest or a modern graft? Although Temple fails to prove its antiquity, the evidence for the recent acquisition of the information is still entirely circumstantial." Additionally, James Clifford notes that Griaule sought informants best qualified to speak of traditional lore, and deeply mistrusted converts to Christianity, Islam, or people with too much contact with whites.

Oberg points out a number of errors contained in the Dogon beliefs, including the number of moons possessed by Jupiter, that Saturn was the furthest planet from the sun, and the only planet with rings. Intrigue of other seemingly falsifiable claims, namely concerning a red dwarf star orbiting around Sirius (not hypothesized until the 1950s) led him to entertain a previous challenge by Temple, asserting that "Temple offered another line of reasoning. 'We have in the Dogon information a predictive mechanism which it is our duty to test, regardless of our preconceptions.' One example: 'If a Sirius-C is ever discovered and found to be a red dwarf, I will conclude that the Dogon information has been fully validated.'

This alludes to reports that the Dogon knew of another star in the Sirius system, Ęmmę Ya, or a star "larger than Sirius B but lighter and dim in magnitude". In 1995, gravitational studies indeed showed the possible presence of a brown dwarf star orbiting around Sirius (a Sirius-C) with a six-year orbital period. A more recent study using advanced infrared imaging concluded that the probability of the existence of a triple star system for Sirius is "now low" but could not be ruled out because the region within 5 AU of Sirius A had not been covered.>>
https://en.wikipedia.org/wiki/Sirius#Discovery_of_Sirius_B wrote:
<<In 1844, the German astronomer Friedrich Bessel deduced from changes in the proper motion of Sirius that it had an unseen companion. On January 31, 1862, American telescope-maker and astronomer Alvan Graham Clark first observed the faint companion, which is now called Sirius B, or affectionately "the Pup". This happened during testing of an 18.5-inch aperture great refractor telescope for Dearborn Observatory, which was one of the largest refracting telescope lenses in existence at the time, and the largest telescope in the United States. Sirius B's sighting was confirmed on March 8 with smaller telescopes.

In 1915, Walter Sydney Adams, using a 60-inch (1.5 m) reflector at Mount Wilson Observatory, observed the spectrum of Sirius B and determined that it was a faint whitish star. This led astronomers to conclude that it was a white dwarf, the second to be discovered. The diameter of Sirius A was first measured by Robert Hanbury Brown and Richard Q. Twiss in 1959 at Jodrell Bank using their stellar intensity interferometer. In 2005, using the Hubble Space Telescope, astronomers determined that Sirius B has nearly the diameter of the Earth, 12,000 kilometres, with a mass 102% of the Sun's.

Since 1894, irregularities have been observed in the orbits of Sirius A and B with an apparent periodicity of 6–6.4 years. A 1995 study concluded that such a companion likely exists, with a mass of roughly 0.05 solar masses- a small red dwarf or large brown dwarf, with an apparent magnitude of >15, and less than 3 arcseconds from Sirius A.

More recent (and accurate) astrometric observations by the Hubble Space Telescope ruled out the existence of such a Sirius C entirely. The 1995 study predicted an astrometric movement of roughly 90 mas (0.09 arcseconds), but Hubble was unable to detect any location anomaly to an accuracy of 5 mas (0.005 arcsec). This ruled out any objects orbiting Sirius A with more than 0.033 solar masses orbiting in 0.5 years, and 0.014 in 2 years. The study was also able to rule out any companions to Sirius B with more than 0.024 solar masses orbiting in 0.5 years, and 0.0095 orbiting in 1.8 years. Effectively, there are almost certainly no additional bodies in the Sirius system larger than a small brown dwarf or large exoplanet.>>
Art Neuendorffer

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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by MarkBour » Fri Oct 30, 2020 11:40 pm

nardes wrote:
Fri Oct 30, 2020 8:21 pm
AnAPODfan wrote:
Fri Oct 30, 2020 5:03 pm
Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.
Hi

The variations in brightness are likely due to capture and processing anomalies as the glare from the diffraction spikes of the Mewlon 210 tended to pollute the Phobos images. Also, depending on which Aligning and Stacking application I used, and what Combine Mode (Mean, Max, Average) I used, I obtained slightly different results.

I have attached a Max Combine stack of the 60 frames, each a 1 sec exposure, taken over a 1 hour period with one exposure every 60 secs, which show the raw orbits of Phobos and Deimos over the 60 mins I was recording. I chose 60 mins as this gave Phobos time to clear the horizontal diffraction spike glare before then being swamped by the glare from the vertical diffraction spike.

I also made a "pretty picture" by using Photoshop Layers to "reveal" the positions of Phobos and Deimos at the start and end of capture, plus mid-point and two points in-between.

Cheers

Dennis
Dennis --
Thanks for the additional information. Your image was well-deserving of today's APOD, quite a fine piece of work! As your last image shows in your additional post, the glare from Mars is really daunting. It goes with what Chris advised, that this is the biggest challenge to overcome to see or capture them.
Mark Goldfain

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Re: APOD: Fear and Dread: The Moons of Mars (2020 Oct 30)

Post by AnAPOD fan » Mon Nov 02, 2020 8:07 pm

Thank you, Dennis! I wasn't sure if it was simply atmospheric aberration, or optics, or perhaps something about the Martian moons themselves. I appreciate your work :)
nardes wrote:
Fri Oct 30, 2020 8:21 pm
AnAPODfan wrote:
Fri Oct 30, 2020 5:03 pm
Question: Is there any particular reason that Phobos appears to be notably brighter at the 22:33:23 time-stamp? It also looks somewhat brighter in the two images just after that, when compared to the first two and the 6th image.
Hi

The variations in brightness are likely due to capture and processing anomalies as the glare from the diffraction spikes of the Mewlon 210 tended to pollute the Phobos images. Also, depending on which Aligning and Stacking application I used, and what Combine Mode (Mean, Max, Average) I used, I obtained slightly different results.

I have attached a Max Combine stack of the 60 frames, each a 1 sec exposure, taken over a 1 hour period with one exposure every 60 secs, which show the raw orbits of Phobos and Deimos over the 60 mins I was recording. I chose 60 mins as this gave Phobos time to clear the horizontal diffraction spike glare before then being swamped by the glare from the vertical diffraction spike.

I also made a "pretty picture" by using Photoshop Layers to "reveal" the positions of Phobos and Deimos at the start and end of capture, plus mid-point and two points in-between.

Cheers

Dennis