APOD: Apogee Full Moon (2014 Jan 18)

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APOD: Apogee Full Moon (2014 Jan 18)

Post by APOD Robot » Sat Jan 18, 2014 5:05 am

Image Apogee Full Moon

Explanation: This big, bright, beautiful Full Moon rose over Lick Observatory Wednesday night. Traditionally a full moon in January might be called the Wolf Moon. But this moon reached its full phase on January 16, 4:54 UT, within about 2 hours of apogee, the most distant point in its elliptical orbit around planet Earth. That also makes it the smallest full moon of 2014. Of course the difference in apparent size between the largest and smallest full moons is hard to see, because the difference in distance between lunar apogee and perigee, or closest point in the Moon's orbit, is only about 50,000 kilometers, while the Moon's average distance is around 385,000 kilometers. Though not by much, this apogee's full moon was also the smallest full moon of the last 1,000 years. It will keep that distinction until a slightly smaller full moon occurs close to apogee in 2154.

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by ta152h0 » Sat Jan 18, 2014 5:12 am

I saw the real thing, the sky in the Pacific Northwest finally cleared up during that event
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Beyond » Sat Jan 18, 2014 5:15 am

So how does the real thing compare to the picture of it :?:
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by saturno2 » Sat Jan 18, 2014 12:41 pm

Apoggeo Jan 16 2014 // 406,536 km ( distance between
Moon and the center of the Earth).
This is the best distance of apoggeo in 1,000 year !!
Very very interesting

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by BDanielMayfield » Sat Jan 18, 2014 4:26 pm

There’s a little bit of blue fringe above the edge of the moon in this photo. Why is this?

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by geckzilla » Sat Jan 18, 2014 4:33 pm

BDanielMayfield wrote:There’s a little bit of blue fringe above the edge of the moon in this photo. Why is this?
http://asterisk.apod.com/viewtopic.php?f=9&t=32740
http://www.atoptics.co.uk/atoptics/gf15.htm
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Chris Peterson » Sat Jan 18, 2014 4:34 pm

BDanielMayfield wrote:There’s a little bit of blue fringe above the edge of the moon in this photo. Why is this?
Any distant luminous object viewed or imaged near the horizon will have its light dispersed like a prism, with short wavelengths at the top and the long ones at the bottom. That's because the atmosphere (like all mediums) has an index of refraction that varies with wavelength.

When I make high magnification images of objects on the horizon, I often repair this color fringing by shifting the blue channel down and the red channel up. Of course, that only works if you don't have well illuminated foreground objects. But maybe that trick was employed with this image? It kind of looks like the observatory has a red fringe on the top, which is what would happen if you defringed the Moon.
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by neufer » Sat Jan 18, 2014 4:42 pm

Click to play embedded YouTube video.
Chris Peterson wrote:
Any distant luminous object viewed or imaged near the horizon will have its light dispersed like a prism, with short wavelengths at the top and the long ones at the bottom. That's because the atmosphere (like all mediums) has an index of refraction that varies with wavelength.

When I make high magnification images of objects on the horizon, I often repair this color fringing by shifting the blue channel down and the red channel up. Of course, that only works if you don't have well illuminated foreground objects. But maybe that trick was employed with this image? It kind of looks like the observatory has a red fringe on the top, which is what would happen if you defringed the Moon.
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by BDanielMayfield » Sat Jan 18, 2014 5:16 pm

geckzilla wrote:
BDanielMayfield wrote:There’s a little bit of blue fringe above the edge of the moon in this photo. Why is this?
http://asterisk.apod.com/viewtopic.php?f=9&t=32740
http://www.atoptics.co.uk/atoptics/gf15.htm
Ah, the answer is “Atmospheric Prismatic Dispersion”. I see that I missed some things from 1/8/14’s discussion. Thanks.
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by ta152h0 » Sat Jan 18, 2014 7:25 pm

Beyond wrote:So how does the real thing compare to the picture of it :?:
not as much fun to have an icecold one staring at a picture
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Boomer12k » Sat Jan 18, 2014 7:37 pm

Interesting.....pardon me if I don't wait around that long to see the next smallest one.....I will no doubt be busy....


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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by neufer » Sat Jan 18, 2014 9:24 pm

http://bigbangtrans.wordpress.com/series-3-episode-23-the-lunar-excitation/ wrote:
The Big Bang Theory
Series 3 Episode 23 – The Lunar Excitation
Scene 1: On the roof of the apartment building.

Leonard: Let me explain what we’re doing here. Um, in 1969, the astronauts on Apollo 11 positioned reflectors on the surface of the moon, and we’re going to shoot a laser off one of them and let the light bounce back into this photomultiplier.

Zack: One question. How can you be sure it won’t blow up?

Leonard: The laser?

Zack: The moon.

Leonard: Don’t worry about the moon. We, we set our laser to stun.

Howard: There it is. There’s the spike!

Leonard: 2.5 seconds for the light to return. That’s the moon! We hit the moon!

Zack: That’s your big experiment? All that for a line on the screen?

Leonard: Yeah, but, uh, think about what this represents. The fact that we can do this is the only way of definitively proving that there are man-made objects on the moon, put there by a member of a species that only 60 years before had just invented the airplane.

Zack: What species is that?
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Nitpicker » Sat Jan 18, 2014 9:42 pm

saturno2 wrote:Apoggeo Jan 16 2014 // 406,536 km ( distance between
Moon and the center of the Earth).
This is the best distance of apoggeo in 1,000 year !!
Very very interesting
Slight correction ... it is not the furthest apogee in 1000 years, it is the furthest full moon. The moon will be slightly further away (406,570 km) later this year: July 28, 03:27 UT, ~1.2 days after new moon.

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by ta152h0 » Sat Jan 18, 2014 9:55 pm

is the laser reflector left on the moon by the Apollo 11 mission still in operation ?
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Chris Peterson » Sat Jan 18, 2014 10:12 pm

ta152h0 wrote:is the laser reflector left on the moon by the Apollo 11 mission still in operation ?
Yes, and regularly used. As a passive device, there's not much to prevent it from operating. It would take an awfully long time to dust over or space weather into uselessness.
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by saturno2 » Sat Jan 18, 2014 10:31 pm

Very well
Thanks Nitpicker
You are right.

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by neufer » Sun Jan 19, 2014 12:30 am

Chris Peterson wrote:
ta152h0 wrote:
is the laser reflector left on the moon by the Apollo 11 mission still in operation ?
Yes, and regularly used. As a passive device, there's not much to prevent it from operating.

It would take an awfully long time to dust over or space weather into uselessness.
  • Offal, n. [Off + fall.] The rejected or waste parts of a butchered animal.
http://lunarnetworks.blogspot.com/2010/03/long-term-degradation-of-optics-on-moon.html wrote:
Long-term degradation of optics on the moon

<<According to the Apollo 15 Surface Journal Comdr. Dave Scott observed that the LRRR looked "super clean" when he and Jim Erwin deployed the mission surface experiments July 31, 1971. He took the cross-Sun view of the LRRR above from the south, showing the orientation gnomon and bubble level. Four times the size of the retro-reflectors deployed by Apollo 11 and Apollo 14, the third and final U.S. LRRR deployed by Apollo 15 is the unit most often detected from Earth. Though lasers and photon detectors have improved many times over in the past four decades, and though First Look at the Apollo landing sites by the Lunar Reconnaissance Orbiter Camera (LROC) last summer showed equipment and astronaut footprints undisturbed, something has been steadily degrading the amount of light these important mirrors are returning back to Earth.>>
http://www.technologyreview.com/view/417911/the-mysterious-degradation-of-the-apollo-reflector-arrays/ wrote:
The Mysterious Degradation of the Apollo Reflector Arrays
March 5, 2010 <<Lunar laser ranging experiments have produced a treasure trove of interesting information about the Moon, for example that it is spiralling away from us at a rate of 38 mm per year.The experiments are simple. Astronomers fire a laser pulse at a reflector placed on the lunar surface by the Apollo 15 mission and then use a telescope to look for the reflection, some 2 seconds later.The observations are challenging. Of the 1017 photons that set out towards the Moon in each pulse, only one makes it back, on average. And only then if seeing conditions are good.

When conditions are good, astronomers often take aim at the arrays left by the Apollo 11 and 14 missions which are only a third of the size of Apollo 15’s and therefore harder to see. If the observers are feeling lucky, they might also try for the Russian Lunakhod 2 array (the Lunakhod 1 array hasn’t been seen since 1971). All in all, astronomers have been taking observations since 1969, first from the MacDonald Observatory in West Texas and later from the Apache Point Observatory in New Mexico . This gives them a substantial database with which to analyse the behaviour of the reflectors.

So how have these reflectors fared in the harsh conditions on the lunar surface over the years? That’s the question addressed today by Tom Murphy at the University of California San Diego and a few buddies. And their analysis poses an interesting problem.

First of all they say that the efficiency of all three Apollo reflector arrays has fallen by an order of magnitude during their sojourn on the Moon. The Lunakhod reflector has fared even worse. When it arrived on the moon in 1973, its signal was 25 per cent stronger than Apollo 15’s. Today it is ten times worse.

What’s happened this gear? The reflectors consist of an array of cubic prisms that operate by total internal reflection. In addition, the Lunakhod prisms have silvered surfaces and are more exposed. Degradation of this silvering probably explains its relative drop in performance.

But what has caused the degradation of the Apollo prisms? Anything that settles on or damages the optical surfaces of the prisms will reduce the efficiency of the total internal reflections. Murphy and co discuss several possibilities such as micrometeorite damage, lunar dust aggregation and the breakdown of the Teflon mounting rings which may have left deposits on the back surface of the prisms. Any of these mechanisms could account for the drop but its hard to pin one down.

However, there is another more intriguing puzzle about the laser ranging data. When the Moon is full, the efficiency of all the Apollo reflectors drops by another factor of ten. Murphy and co have ruled out ground-based effects such as the saturation of their photon detectors when the moon is bright.

So why does this happen? One clue comes from the study of returns during total lunar eclipses. Within 15 minutes of an eclipse occurring, the efficiency of the reflectors returns to its normal levels. When the eclipse ends and the Moon is full again, the efficiency immediately drops again. That strongly points to a thermal effect. When the Sun is low in the lunar sky, its rays cannot directly enter the prisms which are recessed in the arrays. But when the Sun is overhead (which is when the Moon appears full on Earth), its rays travel directly into the prisms. This is probably heating the prisms, distorting them and reducing the efficiency of their reflections.

But why now? The full Moon effect was not a problem in the early days of lunar ranging.

“Dust is perhaps the most likely candidate for the observed degradation,” say Murphy and co. The sunlight is probably absorbed by dust on the optical surfaces which in turn heats the silica prisms. Dust is known to hover above the lunar surface because of electrostatic forces and micrometeorite impacts probably send a few puffs into the lunar atmosphere on a regular basis.

Interesting work. And one that is of more than passing interest for many astronomers because it has implications for anybody thinking of sending gear to the Moon in future. Various astronomers want to send telescopes to the Moon, particularly the far side because of the tremendous seeing conditions there and its isolation from the Earth. Knowing how the Apollo gear has fared will be crucial when it comes to designing this stuff.>>
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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by BDanielMayfield » Sun Jan 19, 2014 1:32 am

neufer wrote:
http://www.technologyreview.com/view/417911/the-mysterious-degradation-of-the-apollo-reflector-arrays/ wrote: Interesting work. And one that is of more than passing interest for many astronomers because it has implications for anybody thinking of sending gear to the Moon in future. Various astronomers want to send telescopes to the Moon, particularly the far side because of the tremendous seeing conditions there and its isolation from the Earth. Knowing how the Apollo gear has fared will be crucial when it comes to designing this stuff.>>
That is very interesting. Solutions could include landing the “gear” in lunar polar craters (where the sun don’t shine). Another would be to include some way to periodically sweep the dust off the optics.

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Re: APOD: Apogee Full Moon (2014 Jan 18)

Post by Anthony Barreiro » Mon Jan 20, 2014 3:55 am

APOD Robot wrote:... Though not by much, this apogee's full moon was also the smallest full moon of the last 1,000 years. It will keep that distinction until a slightly smaller full moon occurs close to apogee in 2154.
Huh. I'm now especially glad I spent some time observing the full Moon Wednesday night.
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