APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Comments and questions about the APOD on the main view screen.
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MarkBour
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by MarkBour » Sun Aug 05, 2018 12:12 am

neufer wrote:
Fri Aug 03, 2018 12:19 am
Sunset, Sat 2040 Sep 8 will be the thing to see.
(I predict a dozen APODs minimum.)
Thanks for emphasizing that one. It's really not too far out on my calendar, and I see I currently have no bookings (except for Sunday afternoon), so I will put it down to watch.

Actually, I wonder if we could get a space-based observation that included a crescent Earth and everything else in one image. Of course, ground-based imagers will be clever enough to catch a mountain range or something so they can count the Earth in their image, and somebody will capture it reflected in a lake, to make the count artificially higher, but I still wonder if there would be anything an off-planet position and a good scope could do that would be extraordinary.

Will people on that side of Earth weigh less than usual that night? Maybe by a yocto kilo, or something?
Mark Goldfain

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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by alter-ego » Sun Aug 05, 2018 4:11 am

MarkBour wrote:
Sun Aug 05, 2018 12:12 am
...
Actually, I wonder if we could get a space-based observation that included a crescent Earth and everything else in one image. Of course, ground-based imagers will be clever enough to catch a mountain range or something so they can count the Earth in their image, and somebody will capture it reflected in a lake, to make the count artificially higher, but I still wonder if there would be anything an off-planet position and a good scope could do that would be extraordinary.
...
In Stellarium, I created this 40° view from geosynchronous orbit. To accentuate the planets, I limited the stellar magnitude visibility to about 6. Note, a thin lunar crescent would also be visible.
 
Sep 8, 2040 - 5-Planet Grouping from 36000km.JPG
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by neufer » Sun Aug 05, 2018 4:17 am

MarkBour wrote:
Sun Aug 05, 2018 12:12 am
neufer wrote:
Fri Aug 03, 2018 12:19 am
Sunset, Sat 2040 Sep 8 will be the thing to see.
(I predict a dozen APODs minimum.)
Thanks for emphasizing that one. It's really not too far out on my calendar, and I see I currently have no bookings (except for Sunday afternoon), so I will put it down to watch.

Actually, I wonder if we could get a space-based observation that included a crescent Earth and everything else in one image. Of course, ground-based imagers will be clever enough to catch a mountain range or something so they can count the Earth in their image, and somebody will capture it reflected in a lake, to make the count artificially higher, but I still wonder if there would be anything an off-planet position and a good scope could do that would be extraordinary.

Will people on that side of Earth weigh less than usual that night? Maybe by a yocto kilo, or something?
Tidal forces (uncompensated by free fall) are dominated by:
  • 1) a close Super Moon plus the Sun at perihelion
    2) a close Venus conjunction
Everything else is under the radar.

Tidal forces scale as the cube of the angular diameter times the density:

Tidal force of a close Super Moon: 132,595 = (34.1')3 x 3.344 g/cm3

Tidal force of Sun at perihelion: 49,232 = (32.7')3 x 1.408 g/cm3

----------------------------------------------------------------------------------------------------
Tidal force of Venus at closest conjunction: 7.223 = (1.1')3 x 5.427 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Jupiter at closest opposition: 0.772 = (0.835')3 x 1.326 g/cm3

Tidal force of Mars at closest opposition: 0.287 = (0.418')3 x 3.9335 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Mercury at closest conjunction: 0.054 = (0.217')3 x 5.243 g/cm3

Tidal force of Saturn at closest opposition: 0.026 = (0.335')3 x 0.687 g/cm3
Art Neuendorffer

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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by BDanielMayfield » Sun Aug 05, 2018 2:42 pm

neufer wrote:
Sun Aug 05, 2018 4:17 am
MarkBour wrote:
Sun Aug 05, 2018 12:12 am
Will people on that side of Earth weigh less than usual that night? Maybe by a yocto kilo, or something?
Tidal forces (uncompensated by free fall) are dominated by:
  • 1) a close Super Moon plus the Sun at perihelion
    2) a close Venus conjunction
Everything else is under the radar.

Tidal forces scale as the cube of the angular diameter times the density:

Tidal force of a close Super Moon: 132,595 = (34.1')3 x 3.344 g/cm3

Tidal force of Sun at perihelion: 49,232 = (32.7')3 x 1.408 g/cm3

----------------------------------------------------------------------------------------------------
Tidal force of Venus at closest conjunction: 7.223 = (1.1')3 x 5.427 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Jupiter at closest opposition: 0.772 = (0.835')3 x 1.326 g/cm3

Tidal force of Mars at closest opposition: 0.287 = (0.418')3 x 3.9335 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Mercury at closest conjunction: 0.054 = (0.217')3 x 5.243 g/cm3

Tidal force of Saturn at closest opposition: 0.026 = (0.335')3 x 0.687 g/cm3
Interesting Q & A y'all. But Mark, notice that Art didn't completely answer your question. He left out some units for you or someonelse to finish the calculation. I could, but it was your question. Oh, and the people on the dayside of the Earth would also feel a little lighter, but they'd be in the dark as to why. :lol2:

Art, interesting that sweet little ole Venus exerts more than 10 times the pull of mighty Jupiter! Girl power!

Bruce
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by neufer » Sun Aug 05, 2018 4:08 pm

BDanielMayfield wrote:
Sun Aug 05, 2018 2:42 pm

Art, interesting that sweet little ole Venus exerts more than 10 times the pull of mighty Jupiter!

Girl power!
And much more tidal pull than her brother Mars.

Just as Selene/Artemis/Diana/Luna exerts more tidal pull than her brother Helios/Apollo:
https://en.wikipedia.org/wiki/Selene wrote:
<<In Greek mythology, Selene (Ancient Greek: Σελήνη "Moon") is the goddess of the moon. She is the daughter of the Titans Hyperion and Theia, and sister of the sun-god Helios, and Eos, goddess of the dawn. She drives her moon chariot across the heavens. In classical times, Selene was often identified with Artemis, much as her brother, Helios, was identified with Apollo. Selene and Artemis were also associated with Hecate, and all three were regarded as lunar goddesses, but only Selene was regarded as the personification of the moon itself. Her Roman equivalent is Luna.>>
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by BDanielMayfield » Sun Aug 05, 2018 6:27 pm

neufer wrote:
Sun Aug 05, 2018 4:08 pm
BDanielMayfield wrote:
Sun Aug 05, 2018 2:42 pm

Art, interesting that sweet little ole Venus exerts more than 10 times the pull of mighty Jupiter!

Girl power!
And much more tidal pull than her brother Mars.

Just as Selene/Artemis/Diana/Luna exerts more tidal pull than her brother Helios/Apollo:
https://en.wikipedia.org/wiki/Selene wrote:
<<In Greek mythology, Selene (Ancient Greek: Σελήνη "Moon") is the goddess of the moon. She is the daughter of the Titans Hyperion and Theia, and sister of the sun-god Helios, and Eos, goddess of the dawn. She drives her moon chariot across the heavens. In classical times, Selene was often identified with Artemis, much as her brother, Helios, was identified with Apollo. Selene and Artemis were also associated with Hecate, and all three were regarded as lunar goddesses, but only Selene was regarded as the personification of the moon itself. Her Roman equivalent is Luna.>>
It's just the straight truth of human nature; gals are more attractive than guys. :wink:

Bruce
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by MarkBour » Sun Aug 05, 2018 9:58 pm

alter-ego wrote:
Sun Aug 05, 2018 4:11 am
In Stellarium, I created this 40° view from geosynchronous orbit. To accentuate the planets, I limited the stellar magnitude visibility to about 6. Note, a thin lunar crescent would also be visible.
 
Sep 8, 2040 - 5-Planet Grouping from 36000km.JPG
That is fantastic.
Mark Goldfain

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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by MarkBour » Sun Aug 05, 2018 10:47 pm

BDanielMayfield wrote:
Sun Aug 05, 2018 2:42 pm
neufer wrote:
Sun Aug 05, 2018 4:17 am
MarkBour wrote:
Sun Aug 05, 2018 12:12 am
Will people on that side of Earth weigh less than usual that night? Maybe by a yocto kilo, or something?
Tidal forces (uncompensated by free fall) are dominated by:
  • 1) a close Super Moon plus the Sun at perihelion
    2) a close Venus conjunction
Everything else is under the radar.

Tidal forces scale as the cube of the angular diameter times the density:

Tidal force of a close Super Moon: 132,595 = (34.1')3 x 3.344 g/cm3

Tidal force of Sun at perihelion: 49,232 = (32.7')3 x 1.408 g/cm3

----------------------------------------------------------------------------------------------------
Tidal force of Venus at closest conjunction: 7.223 = (1.1')3 x 5.427 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Jupiter at closest opposition: 0.772 = (0.835')3 x 1.326 g/cm3

Tidal force of Mars at closest opposition: 0.287 = (0.418')3 x 3.9335 g/cm3
----------------------------------------------------------------------------------------------------
Tidal force of Mercury at closest conjunction: 0.054 = (0.217')3 x 5.243 g/cm3

Tidal force of Saturn at closest opposition: 0.026 = (0.335')3 x 0.687 g/cm3
Interesting Q & A y'all. But Mark, notice that Art didn't completely answer your question. He left out some units for you or someonelse to finish the calculation. I could, but it was your question. Oh, and the people on the dayside of the Earth would also feel a little lighter, but they'd be in the dark as to why. :lol2:

Art, interesting that sweet little ole Venus exerts more than 10 times the pull of mighty Jupiter! Girl power!

Bruce
So, the Moon can reduce my weight when it is overhead (if it's a Super Moon) by 1.3 x 10-7 g and the Sun by 5.0 x 10-8 g. Then when we get an eclipse, the effect can be as strong as 1.8 x 10-7 g, summing those together. Then according to Art's calculations, even if everything else lined up perfectly and under unrealistically good conditions for all of them, they would not total more than 8.4 x 10-12 g, I think. Anyway, so just an eclipse event affects my weight by about 0.2 micro grams, and the others are in the realm of a few pico grams. My guess of a yocto gram was too low.

And thanks for the reminder, Bruce, the folks on both sides of the Earth would feel lighter.
Mark Goldfain

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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by alter-ego » Mon Aug 06, 2018 2:21 am

MarkBour wrote:
Sun Aug 05, 2018 10:47 pm
...
So, the Moon can reduce my weight when it is overhead (if it's a Super Moon) by 1.3 x 10-7 g and the Sun by 5.0 x 10-8 g. Then when we get an eclipse, the effect can be as strong as 1.8 x 10-7 g, summing those together. Then according to Art's calculations, even if everything else lined up perfectly and under unrealistically good conditions for all of them, they would not total more than 8.4 x 10-12 g, I think. Anyway, so just an eclipse event affects my weight by about 0.2 micro grams, and the others are in the realm of a few pico grams. My guess of a yocto gram was too low.

And thanks for the reminder, Bruce, the folks on both sides of the Earth would feel lighter.
Indeed, yocto is too small a prefix. However, you've significantly underestimated your weight reduction which = Δg/g x Weight = 1.8 x 10-7 x Weight. Normalizing to 1 pound and converting to gram-force = 454 gm-force/lb, the weight reduction = 82 microgram-force per pound of weight. So for a 175lb person, their weight reduction = 14 "milligrams".
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by neufer » Mon Aug 06, 2018 12:03 pm

alter-ego wrote:
Mon Aug 06, 2018 2:21 am
MarkBour wrote:
Sun Aug 05, 2018 10:47 pm
...
So, the Moon can reduce my weight when it is overhead (if it's a Super Moon) by 1.3 x 10-7 g and the Sun by 5.0 x 10-8 g. Then when we get an eclipse, the effect can be as strong as 1.8 x 10-7 g, summing those together. Then according to Art's calculations, even if everything else lined up perfectly and under unrealistically good conditions for all of them, they would not total more than 8.4 x 10-12 g, I think. Anyway, so just an eclipse event affects my weight by about 0.2 micro grams, and the others are in the realm of a few pico grams. My guess of a yocto gram was too low.

And thanks for the reminder, Bruce, the folks on both sides of the Earth would feel lighter.
Indeed, yocto is too small a prefix. However, you've significantly underestimated your weight reduction which = Δg/g x Weight = 1.8 x 10-7 x Weight. Normalizing to 1 pound and converting to gram-force = 454 gm-force/lb, the weight reduction = 82 microgram-force per pound of weight. So for a 175lb person, their weight reduction = 14 "milligrams".
Eclipses are unnecessary, of course. A Super Moon (or a Super New Moon) is already lined up sufficiently.
https://physics.stackexchange.com/questions/22613/lowest-gravity-on-earths-surface wrote:
<<[Sea level] gravitational acceleration at the equator is 9.8144 m/s2, vs 9.8322 m/s2 at the poles;

the International Gravity Formula can help, giving 9.761 m/s2 atop Chimborazo.>>

– Dave Jarvis Dec 30 '15 at 3:03
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by MarkBour » Tue Aug 07, 2018 4:47 pm

alter-ego wrote:
Mon Aug 06, 2018 2:21 am
... you've significantly underestimated your weight reduction which = Δg/g x Weight = 1.8 x 10-7 x Weight. Normalizing to 1 pound and converting to gram-force = 454 gm-force/lb, the weight reduction = 82 microgram-force per pound of weight. So for a 175lb person, their weight reduction = 14 "milligrams".
Thanks alter-ego, for clarifying that. How did you know my weight? 14 milligrams actually sounds measurable!
neufer wrote:
Mon Aug 06, 2018 12:03 pm
Eclipses are unnecessary, of course. A Super Moon (or a Super New Moon) is already lined up sufficiently.
https://physics.stackexchange.com/questions/22613/lowest-gravity-on-earths-surface wrote:
<<[Sea level] gravitational acceleration at the equator is 9.8144 m/s2, vs 9.8322 m/s2 at the poles;

the International Gravity Formula can help, giving 9.761 m/s2 atop Chimborazo.>>

– Dave Jarvis Dec 30 '15 at 3:03
I actually would like to go to the summit of Chimborazo some day. Sounds easier than Everest* and it's the point on the surface of the Earth that is farthest from the center (much farther than Everest).

It would make some sense that it would be the point on the surface with the lowest gravity, but I know that mass concentrations in the Earth make this a complex question. I realize you didn't make the claim that it was the *lowest* gravity. Surely it is a good contender. I found this reference, but it is a little older than yours:
https://www.newscientist.com/article/dn ... -extremes/
Mount Nevado Huascarán in Peru has the lowest gravitational acceleration, at 9.7639 m/s2, while the highest is at the surface of the Arctic Ocean, at 9.8337 m/s2.
I have heard that climbers on these peaks have reported feeling light-headed. :-)

* Evidently climbing Chimborazo is still a dangerous climb, the worst danger being avalanches. And I don't want to be cocky, it is likely beyond my capabilities. But the air pressure is far more tolerable. Air pressure is a very complex issue, itself, but there are extensive observations. The Himalayas are definitely the lowest air pressure on the planet, and Chimborazo is not too bad.
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Re: APOD: One Night, One Telescope, One Camera (2018 Jul 28)

Post by neufer » Tue Aug 07, 2018 6:19 pm

MarkBour wrote:
Tue Aug 07, 2018 4:47 pm
alter-ego wrote:
Mon Aug 06, 2018 2:21 am

... you've significantly underestimated your weight reduction which = Δg/g x Weight = 1.8 x 10-7 x Weight. Normalizing to 1 pound and converting to gram-force = 454 gm-force/lb, the weight reduction = 82 microgram-force per pound of weight. So for a 175lb person, their weight reduction = 14 "milligrams".
Thanks alter-ego, for clarifying that. How did you know my weight? 14 milligrams actually sounds measurable!
  • Not to be cocky but 14 milligrams of generic Viagra just cost me $5.75 :|
MarkBour wrote:
Tue Aug 07, 2018 4:47 pm
neufer wrote:
Mon Aug 06, 2018 12:03 pm

Eclipses are unnecessary, of course. A Super Moon (or a Super New Moon) is already lined up sufficiently.
https://physics.stackexchange.com/questions/22613/lowest-gravity-on-earths-surface wrote:
<<[Sea level] gravitational acceleration at the equator is 9.8144 m/s2, vs 9.8322 m/s2 at the poles;

the International Gravity Formula can help, giving 9.761 m/s2 atop Chimborazo.>>

– Dave Jarvis Dec 30 '15 at 3:03
I actually would like to go to the summit of Chimborazo some day. Sounds easier than Everest* and it's the point on the surface of the Earth that is farthest from the center (much farther than Everest).

It would make some sense that it would be the point on the surface with the lowest gravity, but I know that mass concentrations in the Earth make this a complex question. I realize you didn't make the claim that it was the *lowest* gravity. Surely it is a good contender. I found this reference, but it is a little older than yours:
https://www.newscientist.com/article/dn ... -extremes/

Mount Nevado Huascarán in Peru has the lowest gravitational acceleration, at 9.7639 m/s2, while the highest is at the surface of the Arctic Ocean, at 9.8337 m/s2.
I have heard that climbers on these peaks have reported feeling light-headed. :-)

* Evidently climbing Chimborazo is still a dangerous climb, the worst danger being avalanches. And I don't want to be cocky, it is likely beyond my capabilities. But the air pressure is far more tolerable. Air pressure is a very complex issue, itself, but there are extensive observations. The Himalayas are definitely the lowest air pressure on the planet, and Chimborazo is not too bad.
  • Higher air density buoyancy can't hurt.
https://en.wikipedia.org/wiki/Chimborazo wrote:
<<The summit of Chimborazo is widely reported to be the farthest point on the surface from Earth's center, with Huascarán a very close second. The summit of the Chimborazo is the fixed point on Earth that has the utmost distance from the center – because of the oblate spheroid shape of the planet Earth, which is "thicker" around the Equator than measured around the poles.[It has been difficult to resolve this issue definitively because of error margins in summit elevations and geoid data. Application of the formula at Earth radius#Radius at a given geodetic latitude shows that the Earth's radius is 520 metres greater at Chimborazo than at Huascaran, with most recent data showing another 5 metres due to local variations in gravity, for a total of 525 metres. Chimborazo's summit is roughly either 20 metres or 40 metres further from the Earth's center than that of Huascaran.] Despite being 2,585 m lower in elevation above sea level, Chimborazo [at 1.5° south] is 2,163 m farther from the Earth's center than the summit of Everest [nearly 27.6° north].>>
Art Neuendorffer