Does anyone know about this phenomenon? My friend Benson Farb, under the charming misimpression that I am some sort of astronomer, sent me the following image, taken by his uncle Henry Farkas, MD.
That’s the Moon on the right, somewhat overexposed. On the left is another image of the Moon — substantially dimmer. So what is going on?
Consulting the Google, I was able to find multiple examples of similar phenomena, but no explicit explanation: see here, here, here, here, here, here. My first guess was that we were glimpsing a giant Death Star that had been hiding behind the Moon, but upon further thought I regretfully concluded that it’s unlikely we would have alien invaders clever enough to build a Death Star but sloppy enough to reveal it prematurely like that.
Actually there is only one sensible explanation: some sort of lensing/reflection phenomenon that is giving rise to multiple images. The two obvious culprits would be the camera lens itself, or the atmosphere. But Henry took the picture in the first place because he saw the ghost image with his naked eyes, so the camera lens is out. Atmosphere it is! This is somewhat corroborated by the fact that different exposures show different separations between the images — something that could be explained by changing atmospheric conditions.
The atmosphere, whose layers can have very different humidity and temperature, can be a very effective reflector and refractor. Here is an image of a “sun pillar,” to show how dramatic the effects can be.
So I’m pretty convinced that the atmosphere is to blame. On the other hand, it’s a little funny that the images aren’t vertically aligned, which is what I would naively expect. And this wouldn’t be the first time that my lack of real-world knowledge steered me dramatically wrong. Anyone familiar with this phenomenon?
As this is a physics blog I did … a physics experiment and just shot the waning gibbous Moon a few minutes ago, in very clear skies with a (different) point & shoot camera but also heavily overexposed. My own ‘ghost’ is there as expected, of a different shape and color due to the different zoom optics (and at a different position relative to the Moon in each frame, depending on where the latter was in the field of view). And yes, at the same time I saw a distinct ghost of the Moon with my own naked eyes, too, of the same size as the Moon, much fainter and overlapping. On the 21st, around full moon, such glare effects would have been even more pronounced. Case closed, I’d say.
Is it related to Sun Dogs and high atmospheric ice crystals?
27. Aaron Sheldon, this particular phenomenon is most likely not. But sun dogs are due to the presence of atmospheric ice crystals. Check out the link provided by by Andrew Cooper (#20).
it sure is gravitational lensing 🙂
I used to get ghost lights when I would put a UV Haze filter on my camera+lens. They would be inverted about the central point from the original/real light.
Atmospheric birefringence.
Of course, camera filters/mirrors can produce the same effect if you wanted to hoax it.
The moon will shift around depending at what angle the front element is to the subject.
Remove front filter (s) or tilt them to correct.
Whats telling to me is the colour of the second moon…
I have seen this effect with the sun (sorry no camera).
http://en.wikipedia.org/wiki/Sun_dog
It’s definitely not a sun (or moon) dog. They are always 22 degrees away from the light source due to the prism effect of ice crystals. Dr. Farkas’s pictures show a second image only to one side of the moon, varying between 0.3 and 2 degrees away, center-to-center.
I agree with Dan Fischer – we are looking at a false 2nd image due to the camera optics, and Dr. Farkas also saw a false 2nd image with the naked eye due to the “optics” of his eyes.
Reginald Selkirk’s comment that a UV/haze filter could have caused the problem might be the answer. My camera typically wears its UV/haze filter all the time, and it was wearing it that evening. My theory is that a scratched UV/haze filter is cheaper to replace than the whole camera would be if the lens got scratched. These superzoom cameras don’t come with removable lenses like the digital SLRs do.
Henry
The effect with the naked eye is likely a distortion effect caused by moisture in the eyes. This can often cause what appears to be a slightly separated double moon (not normally as much as in the photos). The different positions of the ghost image are probably because the camera moved slightly during the shot. Were these shots handheld or on a tripod?
Sun pillars are caused by plate crystals lying roughly horizontally in the sky. The larger the deviation from the horizontal, the taller the column. Changes in density and moisture levels in the sky don’t change this. Refraction effects can cause distortion of the moon by splitting the colours (green at the top, red at the bottom) like in this image (http://www.flickr.com/photos/jonstraveladventures/4515662196/sizes/o/), but this always happens very close to the horizon and is only ever a very small effect.
“the phenomenon is orders of magnitude brighter than any light pollution-lit cloud could ever be”
The photo was taken just NE of Baltimore, Maryland. It’s one of the most light polluted spots in the country. It’s Bortle class is 8 or 9. See http://novac.com/lp/lightmaps.php for the light pollution map of Maryland and compare with the latitude / longitude given.
In such areas, the light from clouds is sufficient to read a newspaper at night. And that light can be reddish orange. For example, see: “Such lights reflect off low clouds and color the sky reddish orange, says astrophotographer Jerry Lodriguss.”
http://www.weatherquesting.com/orange-skies.htm
“(and there were no clouds anyway, as he said)”
When you see something in the sky you need to take into account the outside chance that it is a cloud.
You can see the cloud for yourself. October 21, 2010 9:07PM EDST is October 22, 2010 01:07 UTC. If you go to http://www.internationalweatherarchive.org/satViewer.aspx you can see for yourself the satellite images of the clouds over the eastern US at this time by setting the satellite to GOES East. (Try to do this before Thanskgiving 2010, as they only keep data for a limited time.)
Set the times to run from say October 21, 11:00 UTC to October 22, 5:00 UTC and run the animation. Chesapeake Bay is prominent, as is the Delmarva peninsula and Delaware Bay. Orient yourself using http://en.wikipedia.org/wiki/Delaware_Bay You can freeze frame the animation.
Note that just north of Maryland, the wind is blowing clouds from a roughly WSW direction, and that new clouds are forming over the north Chesapeake Bay. It’s fairly cloudy by 05:15 which is four hours after the photographs were taken. So while it might have been “clear” at the time the photo was taken, a small volume of slightly cooler air could form a solitary cloud before the majority.
If you’re interested, you might look up the type of cloud that is forming, figure out its altitude, and determine the wind speed and direction from trigonometry.
Carl, I see that there were clouds in the sky from the satellite, but the images in the photo just don’t look very cloud-like to me. I agree that there can be some very strange cloud effects, but the speed, shape and colour of the image just don’t add up to me.
Henry, as the images were taken a few seconds apart, if it is an object, rather than an optical artifact, it was moving fairly quickly across the sky. Did you see it moving at this speed or was the image you saw somewhat more stationary?
“And that light can be reddish orange.”
Or, as the FAQ in the student orientation booklet at the University of Chicago put it, “Why is the sky orange at night?” For those students moving there from less light-polluted areas…
Then I became an astronomer, and now quite like sodium lamps, and hate LED streetlights, because they contaminate our entire goddam spectrum, not just a couple narrow emission lines.
Socorro NM had the opposite problem from Chicago. It had (and probably still has) amazingly clear skies when I was a grad student there. One summer an astrophysics postdoc specializing in radio observations (who grew up in NY city and got his PhD at Baltimore) came out to work at the nearby VLA. In conversation I found out that he was unaware that the milky way was visible to the naked eye. So I got him up one moonless morning at 4AM. We went out into the empty desert mountains and saw the milky way run from horizon to horizon. The galaxy’s light was so bright that the constellations were difficult to discern.
Case closed #26.
The phenomenon of double or even multiple images of the sun and moon has been recorded in the past and is real. You can find a description along with some literature references of observations in M.G.J. Minnaert’s book “Light and Color in the Outdoors” (paragraph 46), latest edition by Springer. It is related to abnormal, sideways refraction.
there was a news report and an article in scientific american that claimed a probe (possibly voyager 1) had captured an image of a reddish sphere apparently approaching our solar system. however within two weeks the whole incident was reported as a lens anomaly. this possible object was not near any known planet or natural satellite. it was in intragalactic space. could this be the same object?
I took the exact same photos from Oct 21-Oct 25th. Here is a time-lapse video I did of some of the photos, taken about 10 seconds apart, camera on tripod. Photos taken in Phoenix, AZ under clear skies.
http://www.youtube.com/watch?v=cily9GcYHPw