Astronomy

Lunar terminator illusion

Lunar terminator illusion

Sometimes, you can see the Moon high in the night sky, which is illuminated from the side where Sun goes down but slightly from above. It is paradoxical when Sun hangs at the lower level above the horizon than the Moon. Sun can even go down behind the horizon, yet, the Moon is illuminated slightly from above.

The paradox is defined in Wikipedia and captured in this video

There is a video from "Vsauce"

http://youtu.be/Y2gTSjoEExc?t=280

which pretends to explain the phenomenon but fails, IMO. From his explanation I only get that light beam should deviate from the direct route to move along the orbital around the Earth, like if it is the Sun or Moon orbit seen from the Earth. But why? The nebular objects orbit because they have mass and gravitationally bound. Why should light beam travelling from Sun to the Moon bend the same way as if it orbits around the Earth? I do not get the explanations.

The popular explanation of the illusion does not hold the water

http://youtube/watch?v=Rsz2QNPprB8&lc=z134gjggimumexwgr04cdxbrnlattlwp5n40k


The light ray does not bend (in fact it does a little bit, but that's small and doesn't matter now). However, what you see is not a path of a ray of light, but a projection of this path on the celestial sphere around you. This projection is an arc of a great circle with you in the centre.


http://www.twitter.com/tweetsauce
http://instagram.com/electricpants
Sources and sites to learn more below.

dolly zoom effect: http://filmmakeriq.com/lessons/introduction-to-the-dolly-zoom/

http://en.wikipedia.org/wiki/Angular_diameter
https://xkcd.com/1276/
http://en.wikipedia.org/wiki/Visual_angle
http://astronomy.swin.edu.au/cosmos/A/Angular+Diameter

great visual angle / angular diameter chart: http://upload.wikimedia.org/wikipedia/commons/f/f8/Comparison_angular_diameter_solar_system.svg

moon terminator illusion resources:

rogers and olga naumenko (2014): http://www.perceptionweb.com/abstract.cgi?id=v1410275
moon tile illusion [PDF]: http://www.seas.upenn.edu/

amyers/MoonPaper20June.pdf
http://www.upenn.edu/emeritus/essays/MyersMoon.html
http://www.astropix.com/HTML/L_STORY/MOONILL.HTM
http://cosmoquest.org/forum/showthread.php?39035-Why-does-the-moon-s-terminator-not-appear-orthogonal-to-the-direction-of-the-sun

the (more famous) moon illusion:

cylindrical perspective animation: http://chrisjones.id.au/MoonIllusion/

http://www.joshuanava.biz/perspective/introduction-1.html
http://design.tutsplus.com/articles/live-perspective-a-new-approach-to-depth-in-drawing--cms-22100
http://www.handprint.com/HP/WCL/perspect1.html
http://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/OWENS/LECT1/node2.html

keystone effect: http://en.wikipedia.org/wiki/Keystone_effect

subjective constancy: http://en.wikipedia.org/wiki/Subjective_constancy

http://www.badastronomy.com/mad/2000/sunbeams.html
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/air/crp.rxml
http://en.wikipedia.org/wiki/Crepuscular_rays#/media/File:Crepuscular_Rays,_India.JPG

lunar phase interactive: http://astro.unl.edu/naap/lps/animations/moonPhasesHorizonDiagram.html

car illusion: http://www.moillusions.com/these-3-cars-are-same-in-size/

star field illusion: https://richardwiseman.wordpress.com/2011/09/08/most-amazing-illusion-ever/

hallway illusion: http://i.imgur.com/ty6PM.gif

Euclid’s Optics: [PDF] http://www.math.cornell.edu/

http://www.nettonet.org/Nettonet/101%20Painting/Studies/perspectivism.htm
http://netfuture.org/fdnc/ch22.html
http://www.reddit.com/r/AskHistorians/comments/1hlox1/why_are_medieval_paintings_so_crappy/
http://www.reddit.com/r/AskHistorians/comments/1kshhk/why_did_ancient_civilizations_never_produce_any/
http://www.reddit.com/r/AskHistorians/comments/1jus85/why_did_realistic_art_only_take_off_in_the_west/
http://www.reddit.com/r/AskHistorians/comments/1d442w/why_was_human_anatomy_poorly_drawn_in_ancient/
http://www.reddit.com/r/AskHistorians/comments/1ceool/why_couldnt_people_draw_realistically_in_the/
http://www.reddit.com/r/AskHistorians/comments/1dz7fr/why_arent_ancientmedieval_paintings_three/
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0049786
http://www.reddit.com/r/askscience/comments/13zsf5/did_artistic_sense_evolve_in_humans/
http://www.zoharworks.com/artandoptics/papers/tyler_fs.html

other geometric illusions: http://en.wikipedia.org/wiki/Geometrical-optical_illusions

MUSIC FROM:
http://www.youtube.com/JakeChudnow
and
http://www.audionetwork.com

Like

An Easy-to-Understand Explanation of the Moon Terminator Illusion

There’s a strange optical illusion that we all experience, without even thinking about it, relating to the way we see the moon. The Moon Terminator Illusion is that weird phenomenon when the side of the moon that is lit by the sun doesn’t look like it actually lines up with the sun at all. Vsauce host Michael Stevens explores the science behind this illusion and explains perspective, angles, and zoom effects involved:

Our vision is influenced by visual clues and past experiences, making us susceptible to optical illusions. From our perspective from the ground, it often doesn’t look like the sunlight is hitting the moon is a straight line. Instead, the line appears curved. That’s the Moon Terminator Illusion. So, what’s going on with our eyes and brain that we see it this way?

First things first, the terminator. A terminator is the term used to describe the line that separates the illuminated and dark side of the moon (or any object).

When we see the illuminated side not aligned with the direction of light creating it, it’s because of visual angles, foreshortening and horizon lines. The same thing happens to our perspective with up-close objects, but the difference is in the clues. The brain is able to use our past experiences and knowledge of the world around us to recognize shapes that are distorted by perspective.

Steven uses a great example of this by simply opening a door. When the door is closed, it is a perfect rectangle. But when opened, the edge closest to us appears bigger, the shape distorted, but we still know the door is rectangular.

A door’s shape appears distorted from an angle.

The Moon Terminator Illusion and Dolly Zoom Effect

When it comes to capturing a scene on camera, our brains can be manipulated because the camera crops out the visual cues we normally rely on.

To better portray this better, Stevens explains the difference between moving and zooming in on a scene and why each produces a different effect or perspective. When moving a camera forward—like when doing a tracking shot—closer objects are more distorted than objects further away from view. But, when zooming in, the entire scene is affected in equal measure.

The Dolly Zoom Effect uses both zooming and moving simultaneously to deliver a trippier effect, which was popularized by Hitchcock in his films. The effect keeps the subject the same size while altering the distance and focal length.

Understanding both the Moon Terminator Illusion and the Dolly Zoom Effect helps us make sense of the strange optical illusions that we see so often. This video does a great job explaining everything. Plus, there are a few fun little experiments you can do to see for yourself how the brain and eyes process what we see.


Shadows on the Moon Make a Point

By: Bob King November 26, 2014 7

Get Articles like this sent to your inbox

Fooled by shadow play into thinking lunar mountains were pointy pinnacles? Learn why we often see them that way.

This sketch of the Caucasus Mountains perfectly captures the dramatic, pointed shadows cast by peaks and promontories in the low sunlight.
Frank McCabe

A few winters back, I noticed that a snowbank illuminated by a nearby yard light cast very long and pointy shadows. That seemed odd, as the bank consisted of rounded humps and knobs. But because the light struck it at a low angle, it greatly exaggerated the relief of each and every chunk, stretching bits of topography into long, sharp "teeth".

The effect was dramatic and immediately recalled nights at the telescope observing the spire-like shadows cast by lunar peaks and craters near the lunar terminator, the moving line separating daylight from darkness on the Moon.

Could the snowbank scenario be playing out on the Moon? At first blush, you wouldn't think so. With no atmosphere or running water to soften its hard edges, it's easy to imagine a jagged lunar landscape of pointy peaks just like what the shadows appear to show. Early depictions of the Moon's surface took their cues from telescopic observation, showing a rugged, forbidding landscape. As it turns out, this is an illusion.

Sunlight grazing the top of a snowbank (right) throws the rounded knobs into stark relief on the street below. Every detail has been stretched and exaggerated by the sun’s low angle to create a shadowy "mountain range".
Bob King

The very fact that the moon is airless allows every bit of meteoric dust to zap the surface at tens of thousands of miles per hour. Over the 4.5 billion year lifetime of the moon, myriad micrometeorite impacts have acted like cosmic sandpaper, grinding down the once craggy peaks into the smooth hills and mountaintops so vividly seen in photographs returned from the Apollo missions.

A 19th-century illustration of how the moon’s surface would look to a visitor from Earth. From the book The Moon by Nasmyth and Carpenter, published in 1874.

Other erosional forces also come into play. The 500-degree difference between daytime and nighttime lunar temperatures undoubtedly acts to weaken and fracture rock. If I can hear the trees popping on a subzero night here at home, I’ll bet rocks shudder during the long lunar night when the temperature bottoms out around –240° F (–151° C) and shudder again when the Sun rises two weeks later and the temperature soars to 250 °F (123 °C).

Peaks of the Taurus-Littrow Mountains, with the command module in the foreground, loom beyond the window of the Apollo 17 lunar module. From a closer perspective, we get a better idea of the relative smoothness of lunar mountains. Have a pair of red-blue glasses? Click the image for an awesome 3-D view of this scene.
NASA

And what of boulders perched atop crater walls and dotting the valleys and slopes? Loosened by temperature change and occasional moonquakes, they tumble downhill, further subduing lunar contours over time. No, our satellite turns out to be a softer-looking place than most had imagined, with mountains that more closely resemble the Appalachians than the Himalayas.

On the ground. Apollo 17 astronaut Jack Schmitt makes his way among the Taurus mountains, which have been smoothed by billions of years of micrometeorite abrasion.
NASA

One of the great pioneers of space art, Chesley Bonestell, who painted breathtaking scenes of rockets landing on a rough and rocky Moon, grumbled when he saw the photos returned by the orbiting lunar probes and landers of the mid-1960s.

Pointed shadows stretch across the floor of the 68-mile-wide crater Plato. The best place to see extreme shadows is right along the Moon's terminator, the ever-shifting boundary between lunar day and night. This is where the Sun is near rising (between New and Full phases) or setting (from Full to New).
Damian Peach

Someone asked Bonestell what he thought about the images. "I thought how wrong I was!" he said. "My mountains were sharp, and they aren't on the Moon. They're round, battered by millions of years of meteorites."

You can watch this shady business play out in the coming week as the Moon waxes from a thick crescent to a three-quarter gibbous. All you need is a small telescope. Use 50x or higher and examine the strip of craters and hills along the lunar terminator lit by the rising Sun.

I've listed a few target areas where isolated peaks in mountain ranges, like the Alps and Caucasus, and along the rim of craters like Plato make for dramatic shadow-casting. Dates shown are approximate times when the terminator cuts through each region.
Virtual Moon Atlas - Patrick Chevalley, Christian Legrande

For evening viewing, the 6-9 day old Moon is best because we face the terminator squarely and shadows display the least amount of foreshortening. But other times work too — just avoid the Full Moon. Keep your wits about you as you enter a land of shadow and illusion!

The Sky & Telescope Field Map of the Moon: the only moon reference you'll need when you're at the telescope!


Main menu

This view last night really puzzled me: it was extraordinary how Bailly and terrain nearby crated a localised hump, or peak, on the terminator, creating an illusion of Bailly being at the cusp of the gibbous phase, but it wasn't. Panning the camera live view gradually along the terminator by slewing the telescope, I was surprised to find that I could keep following the terminator way to the lunar south (right in this image), at least two fields beyond this view, till the terminator turned into the limb.

I've never seen this phenomenon before, and it is not represented in the Moon simulation app I used to show the terminator at this date and time, Moon Globe HD (iOS). It's also not shown quite like this in any on-line images I've found of this area.

I wonder if this is a known thing: is it an unusual consequence of a particular libration and phase?

It sees to me it can only be explained by this area of the lunar crust around Bailly having a substantial large-scale uplift and deviation from the spherical.


The Lake County Astronomical Society

The first quarter moon is a popular phase for many lunar observers because it's easy to observe and has lots of detail. For one thing, it's well up in the sky when the sun sets, and it stays up until about midnight.

I took the following photograph* just at first quarter phase and oriented the moon as it appears in most astronomical telescopes, with south up and the image reversed right-to-left. Although the illuminated half of the moon is facing to the west as seen in our sky -- toward the sun -- this is actually the lunar east side.

While a thin crescent moon low in the west may be dramatic, a telescope shows a fairly bland surface at the edge, or limb, of the moon. Recall that when we're looking toward the limb of the moon, we're seeing the features at an oblique angle, which means things like craters are considerably foreshortened -- they appear long and narrow. But at first quarter, we're seeing features toward the center of the moon in a more face-on aspect.

Experienced moon watchers plan their observing to catch certain features when they're near the terminator. The terminator is the edge between the light and dark parts of the moon. It's the point of lunar sunrise or sunset, so features stand out boldly here due to the longer shadows. In the photo, you can pick out features that are just partly illuminated they appear as little points of light just beyond the terminator. These are mountain peaks or the high points of crater walls that are catching the first rays of a rising sun, while their bases are still in darkness. The lack of shadows on a full moon explains why many features seem to disappear from view at that time of the lunar month.

Notice that around first quarter there's some difference in the types of features visible between the northern and southern hemispheres. In the north ("down" in the photo), there's an abundance of maria (the dark "seas"). On the other hand, there's an abundance of rugged craters in the southern hemisphere around the central meridian, which is why this area is often referred-to as the "Southern Highlands". Note too that, unlike in the south, there are a number of long mountain ranges in the north. These mountain ranges are especially prominent around the large Mare Imbrium basin, which lies just at the terminator and is only partially visible at this phase. Mare Imbrium is one of the most highly detailed areas of the moon, and with each succeeding night, more of it becomes visible as the terminator marches toward the lunar west.

If you recall the differences in topography, you won't get lost when visiting the moon via telescope. At least you'll know which hemisphere you're in! Finally, if you become expert on the surface features of the moon, you could add the title "selenographer" to your resume. (Selenography is the lunar equivalent of geography on the Earth.)

* Info on the photo: negative projection (using a Barlow lens without a telescope eyepiece or camera lens) through a 4-inch refractor at 1/8 second on Kodacolor Gold 400 film. It's a composite of two photographs that were scanned and combined electronically using Adobe Photo DeLuxe software, after which the image was converted to grey scale.


Terminator

No, this isn’t a movie about robots. The terminator is the line that separates day from night on an object lit by a star. You can see evidence of this terminator when you look at the Moon. When we see the Moon, half in light and half in darkness, we’re seeing the terminator line going right down the middle of the Moon.

From our perspective here on Earth, we see the Sun rise from the East, go through the sky and then set again in the West. But if you could see the Earth from space, you would see half the planet is always illuminated, and half the planet is always in shadow. Since the Earth is rotating, we can watch different parts of the planet illuminated, and other parts darkened. The people on the surface of the planet are experiencing the Sun moving through the sky, but really it’s them who are doing the moving.

The location of the terminator depends on the axial tilt of the object. Since the Earth is tilted by 23.5° away from the Sun’s axis, the position of the terminator changes depending on the season. During summer in the northern horizon, the Earth’s north pole never goes into shadow, so the terminator never crosses the pole. And then in winter in the northern horizon, it never comes out of shadow.

If you could orbit the Earth, just above the equator, you would see the terminator line speeding away at approximately 1,600 km/h (1000 miles per hour). Only the fastest supersonic aircraft can match the terminator’s speed. But as you get closer to the poles, the terminator moves more slowly. Eventually at the poles, you can walk faster than the speed of the terminator.

When you see a terminator from afar, it can tell you a lot about a planet or moon. For example, the Earth’s terminator is fuzzy. This means that our planet has a thick atmosphere that scatters the light from the Sun. The Moon, on the other hand, is airless, so its terminator is a crisp line. When you’re standing on the surface of the Moon, it’s either bright or dark, not the in-between twilight that we experience here on Earth.

We have written many articles about the terminator for Universe Today. Here’s an article about why the Sun rises in the East and sets in the West, and here are some Earthrise photos.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.


Scorpius and the "moon illusion"

Hi everyone! I'm new here and I'm glad to be a member at this great website! This is my first post, so I hope it's
not in the wrong place. Please bear with me!

Most of us have experienced the "moon illusion", where the
moon looks much bigger when it's low in the sky, rising or
setting. I confess I don't understand it, but I've thought about it a lot. I've also noticed the same effect when
observing certain constellations - especially one of my
favorites - Scorpius. As I live in the northeast (upstate
NY) at latitude +42*, this beautiful constellation is always
low near my south horizon, where it literally SPRAWLS there!
However I remember when, while serving in Vietnam (much
farther south, at latitude +15*) back in 1966, it was higher
in the sky and much more compact. And then I remembered the
"moon illusion".

Since then, I've often wondered if this phenomenon has
something to do with our atmosphere. Since we have to look
through much more of it when observing objects low near the
horizon, could it possibly have some sort of "lensing"
effect on what we see? I guess this sounds crazy, but I've
always been fascinated by this effect!

My eyesight might not have been perfect, and I admit that I
had my mind on more stressful matters back then (!), but
there was no doubt that Scorpius was brighter and much more
compact as I observed it in that long-ago, far-away sky.

Would you please share your thoughts with me on this.
And again, thanks for bearing with me!

#2 Tim A.

First, Welcome to CN, the best astro site on the web, bar none!

Next: It's not an atmospheric phenomenon, as many photographs prove. Photographed at the horizon and at higher elevations, the moon is always the same size.

It's a psychological phenomenon, a most interesting one. There are a lot of theories, none of which seems iron-clad to me. But there it is, a giant moon on the horizon shrinks to 'normal' proportions as it rises. I just enjoy it for what it is. (I've seen far stranger psychological phenomena, believe me!)

#3 JerryK

Personally, I subscribe to the Relative size hypothesis, but you can chose out of several theories:
http://en.wikipedia. i/Moon_illusion

#4 contrailmaker

Sorry, but there is quite a bit of lensing effect from the atmosphere. It is most pronounced when viewing from high elevations or, in my case, altitudes. It, in fact makes the moon look smaller when near the horizon squished in the vertical. The lensing effect is also apparent when you draw a perpendicular line from the edges of the lunar terminator and that line does not coincide with the position of the sun. Again, greatly amplified when either the sun or the moon are near the horizon.

#5 garyc11

#6 GlennLeDrew

To amplify on what contrailmaker said.

Indeed, the atmosphere induces a 'lensing' effect, but it works pretty much exclusively in the vertical direction due to the density profile of the atmosphere. Atmospheric refraction is in effect for all angles except the perpendicular, but it generally becomes readily visible only at angles within a couple or few degrees of the true horizon.

Under normal atmospheric conditions refraction 'squishes' objects vertically. But in anomalous conditions, such as during temperature inversions, some vertical 'stretching' can be seen.

At any rate, the only horizontal refraction that can occur is of very small scale, such as when air masses/parcels having differing temperatures mix. The visible manifestation is a kind of turbulent roiling of the view. (To see this, open your door on a cold day.)

The upshot is that here can never be sufficient refraction to enlarge an object both vertically *and* horizontally. And any vertical component would rarely exceed a mere 1/2 degree (and that could only occur barely above the horizon, to boot.)

#7 contrailmaker

There is a horizontal component of the lensing effect that goes almost unnoticed because it is just about impossible to notice on extended objects like the moon. Hence my reference to the perpendicular line and the sun. Old aerial navigation star charts had to be used with data books to account for all sorts of corrections including those for when the stars were measured near the horizon. There is a real lensing effect at work here as well as atmospheric diffraction effects and temperature effects.

I learned that back when a navigator was a highly trained career officer working his aXX off to put the carrot in front of us to steer in the right direction. Now a navigator is a box named Garmin. Man I'm getting old.

#8 Star46

Thanks for the replies so far, guys! This is becoming a
learning experience for me, as there seem to be many intriguing theories re this fascinating phenomenon!

Thanks for the welcome, Tim A. and garyc11! Gary, I see you're from Niagara Falls. I'm from the western Catskills
(from Long Island, originally), and, sadly, tend to get
depressed and cut down on observing every winter sometimes
it's almost TWO WEEKS between clear nights up here! I wish I could move to the southwest - to New Mexico or Arizona,
for instance - but I doubt if I'll ever get there. I hope
you do better at your locale.

#9 Tim A.

Sorry, but there is quite a bit of lensing effect from the atmosphere.

#10 contrailmaker

Sorry, but there is quite a bit of lensing effect from the atmosphere.

#11 deSitter

Try this. Hold an object up to your TV screen that matches its size as seen from your normal position across the room.

Now view that object against your lap, or something else in the foreground, using the same arm's length as before.

You'll be astonished at how small your screen really is.

The astronaut Jim Lovell likes to talk about how he could blot out the Earth with his thumb. Even so, the Earth in the lunar sky at 2 full degrees would seem huge. The visual system is trained to deal with relatively small regions, because most everything you see around you is actually very small in angular size. When seen in the context of buildings and trees which are themselves of small angular size, even the 1/2 degree Moon can appear huge.

(Example - a football seen from 100 yards subtends and angle of only 11 arc minutes - 1/5 degree. A baseball seen emerging from the pitcher's hand while standing at home is only 14 arc minutes - half the diameter of the Moon!)

#12 FLYcrash

#13 Star46

Summer will, of course, come again but I couldn't wait!
Taking a tip from the late, great Leslie Peltier in his
classic "Starlight Nights", I stayed up all night just to see my old fiery friend, Antares, rise once again!

Scorpius (about half of him, at least) is large in the south - and the "moon illusion" is still playing tricks.
But I'm still amazed! Maybe it's better to just enjoy than
try to figure it out.

#14 skysurfer

Attached Thumbnails

#15 edosaurusrex

One of the thngs I secretly like about participating in a Messier Marathon is to see Scorpius rising. As a kid in Cleveland, OH I used to stay up until 1am in late June and set up my 60mm refractor on the garage roof to see the Scorpius Jewel Box and M's 6 and 7. Trees were a bigger problem than south suburban streetlights back then.

#16 Star46

Thank you, skysurfer, for the shot of Orion on his back -
with Sirius to his lower right and Aldebaran to his upper
left! We never get to see him in this position in the northeast USA. I assume the further south we go, he's
upside-down? Somehow, I just can't imagine that proud
personage standing on his head!

#17 GlennLeDrew

#18 garyc11

#19 star drop

Hi everyone! I'm new here and I'm glad to be a member at this great website! This is my first post, so I hope it's
not in the wrong place. Please bear with me!

Most of us have experienced the "moon illusion", where the
moon looks much bigger when it's low in the sky, rising or
setting. I confess I don't understand it, but I've thought about it a lot. I've also noticed the same effect when
observing certain constellations - especially one of my
favorites - Scorpius. As I live in the northeast (upstate
NY) at latitude +42*, this beautiful constellation is always
low near my south horizon, where it literally SPRAWLS there!
However I remember when, while serving in Vietnam (much
farther south, at latitude +15*) back in 1966, it was higher
in the sky and much more compact. And then I remembered the
"moon illusion".

Since then, I've often wondered if this phenomenon has
something to do with our atmosphere. Since we have to look
through much more of it when observing objects low near the
horizon, could it possibly have some sort of "lensing"
effect on what we see? I guess this sounds crazy, but I've
always been fascinated by this effect!

My eyesight might not have been perfect, and I admit that I
had my mind on more stressful matters back then (!), but
there was no doubt that Scorpius was brighter and much more
compact as I observed it in that long-ago, far-away sky.

Would you please share your thoughts with me on this.
And again, thanks for bearing with me!


The Moon’s terminator line contradicts the Copernican Theory

According to Heliocentric Cosmology, the lunar terminator is the boundary dividing the sunlit portion of the moon and the unlit portion of the moon causing a solar twilight on the lunar surface. The lunar terminator travels along the lunar surface per the rotational speed of the moon around its axis and its orbital period around the Earth.

Termed the Terminator Illusion, an observer on the ground is able to view the unlit portion of the lunar surface facing the sun’s directional light. Conversely an observer on the ground is also able to view the lit portion of the lunar surface facing away from the sun’s directional light. Both of which contradicts the globe model in its entirety. This “Terminator Illusion” is no illusion at all due to the fact that this celestial phenomenon is readily viewable to the naked eye.

Modern science tells us that the sun travels roughly seven times faster than the speed of the moon across the sky, in which case the lunar terminator should have a noticeable change throughout the day as the sun travels past the moon rather than staying fixed in one position on the lunar surface.

Disregarding what classical astronomy has taught us over the past 500 years, physical observations of the moon’s terminator not coinciding with the sun’s directional light during daytime lends credence to an even higher possibility that we live in a geocentric creation.


Gruithuisen's Lunar City

This area has generated some interest (about 1/2 way down in this thread) over in the Deep Sky forum, so I offered to open a thread here for anyone interested.

Gruithuisen's Lunar City is the result of a combination of geological features which Franz von Gruithuisen fancied to be a structured lunar city. The area is pretty large, stretching from 8N-4N to 6W-10W, just north of crater Schroter.

Here's Gruithuisen's 1824 sketch of the 'city' (reflector orientation), and here's the LAC chart.

Does anyone have any images of this area? I'll sift through mine and see if anything turns up.

#2 trainsktg

Wasn't there one in the latest S&T?

#3 frank5817

Attached Thumbnails

#4 vikingcraftsman

#5 Carol L

Sorry Keith, I don't get S&T anymore, but will check the library's copy on my next trip to town. thanks!

No apolgies needed Frank, your wide-area image shows the location of the Lunar City quite well.
It's the large-ish dark area in the upper left quarter. Together with Copernicus and Eratosthenes, it forms a triangle. Crater Shroter is on the upper edge of the image, about 1/4 of the way in from the left side.

You're welcome, Vikingcraftsman!

As it turns out, all I could find in my image folders was one pic from mid-September of this year. This area's surrounded by great photo targets which is probably why it's so overlooked. an ugly duckling of sorts.

Got some more info on the feature, though. In searching online for a larger image of the Gruithuisen sketch (couldn't find one), there was an entry of interest in the Project Gutenberg site's copy of Thomas Gwyn Elger's book The Moon - A Full Description and Map of its Principal Physical Features:

"SCHROTER.--A somewhat larger formation, with a border wanting on the S. Schmidt draws a considerable crater on the S.W. side of the floor. It was in the region north of this object, which abounds in little hills and low ridges, that in the year 1822 Gruithuisen discovered a very remarkable formation consisting of a number of parallel rows of hills branching out (like the veins of a leaf from the midrib) from a central valley at an angle of 45 deg., represented by a depression between two long ridges running from north to south. The regularly arranged hollows between the hills and the longitudinal valley suggested to his fertile imagination that he had at last found a veritable city in the moon--possibly the metropolis of Kepler's _Subvolvani_, who were supposed to dwell on that hemisphere of our satellite which faces the earth. At any rate, he was firmly convinced that it was the work of intelligent beings, and not due to natural causes. This curious arrangement of ridges and furrows, which, according to Webb, measures about 23 miles both in length and breadth,
is, owing to the shallowness of the component hills and valleys, a very difficult object to see in its entirety, as it must be viewed when close to the terminator, and even then the sun's azimuth and good definition do not always combine to afford a satisfactory glimpse of its ramifications. M. Gaudibert has given a drawing of it in the _English Mechanic_, vol. xviii. p. 638."

Here's my image along with inserts, showing a guesstimate of the features Gruithuisen sketched. My image was taken during the waning phase, and from the looks of it Gruithuisen made his sketch during the waxing phase.
That's great news, because I toggled the terminator line in the VMA and the area is in position the same night as the Straight Wall.. and thats coming up on Tuesday. this would make a great target for the lunation thread!


Watch the video: The Moon Terminator Illusion (October 2021).