APOD: Love and War by Moonlight (2015 Feb 26)

[APOD Robot]

Love and War by Moonlight

Explanation: Venus, named for the Roman goddess of love, and Mars, the war god's namesake, came together by moonlight in this lovely skyview, recorded on February 20 from Charleston, South Carolina, USA, planet Earth. Made in twilight with a digital camera, the three second time exposure also records earthshine illuminating the otherwise dark surface of the young crescent Moon. Of course, the Moon has moved on from this much anticipated triple conjunction. Venus still shines in the west though as the evening star, third brightest object in Earth's sky, after the Sun and the Moon itself. Seen here within almost a Moon's width of Venus, much fainter Mars approached even closer on the following evening. But Mars has since been moving slowly away from brilliant Venus, though Mars is still visible too in the western twilight.

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[Nitpicker]

Nice one.

[marson]

Pretty for something so simple.

To pick a nit, why say "digital camera" instead of "camera"? Digital is default today.

[Chris Peterson]

To pick a nit, why say "digital camera" instead of "camera"? Digital is default today.

Habit by those who grew up with film? I prefer "electronic camera" since the sensors which have replaced film are fundamentally analog devices, not digital ones.

[bactame]

Yes this image is great but doesn't show enough of the dark side. Anybody seen the Netflix film "Aliens on the Moon"? It shows quite a bit and raises the question of an extended family of man on the dark side. Most of it is provocative at best but raises the question that we might have friends out there.

[Chris Peterson]

Yes this image is great but doesn't show enough of the dark side. Anybody seen the Netflix film "Aliens on the Moon"? It shows quite a bit and raises the question of an extended family of man on the dark side. Most of it is provocative at best but raises the question that we might have friends out there.

The dark side? What's that? The Moon has no permanently dark side. It's night on part of the surface we see here, but that's always changing. Maybe you mean the far side of the Moon? We have many images of that, although we obviously can't make any from the Earth.

[Ron-Astro Pharmacist]

Is it difficult to predict when Venus may occult Mars as seen from Earth? They were obviously very close February 22nd but I can't find a future prediction for another occultation of that type.

A Wiki search of "History of Mars observation" lists the below.
"On October 13, 1590, the German astronomer Michael Maestlin observed an occultation of Mars by Venus…"
From: Breyer, Stephen (March 1979). "Mutual occultation of planets". Sky and Telescope 57 (3): 220.

http://www.seasky.org/astronomy/astrono ... rrent.html

[Indigo_Sunrise]

Is it difficult to predict when Venus may occult Mars as seen from Earth? They were obviously very close February 22nd but I can't find a future prediction for another occultation of that type.

A Wiki search of "History of Mars observation" lists the below.
"On October 13, 1590, the German astronomer Michael Maestlin observed an occultation of Mars by Venus…"
From: Breyer, Stephen (March 1979). "Mutual occultation of planets". Sky and Telescope 57 (3): 220.

http://www.seasky.org/astronomy/astrono ... rrent.html

I just read an article about this very thing, (Venus occulting Mars, as seen from Earth). IIRC, it seems as though it is so infrequent, as in 'lining up' only every thousand years or so. I'll see if I can find where I was reading it.......


ETA: From here:

An occultation involving two planets is extremely rare, however. For instance, the last time Venus occulted Mars was on October 13, 1590, and the next time will be June 4, 2327.

This image is an awesome-almost-occultation!

[MarkBour]

All's fair in this image !
Especially Venus, with so many radiating lines.

[Ron-Astro Pharmacist]

Is it difficult to predict when Venus may occult Mars as seen from Earth? They were obviously very close February 22nd but I can't find a future prediction for another occultation of that type.

A Wiki search of "History of Mars observation" lists the below.
"On October 13, 1590, the German astronomer Michael Maestlin observed an occultation of Mars by Venus…"
From: Breyer, Stephen (March 1979). "Mutual occultation of planets". Sky and Telescope 57 (3): 220.

http://www.seasky.org/astronomy/astrono ... rrent.html

I just read an article about this very thing, (Venus occulting Mars, as seen from Earth). IIRC, it seems as though it is so infrequent, as in 'lining up' only every thousand years or so. I'll see if I can find where I was reading it.......


ETA: From here:

An occultation involving two planets is extremely rare, however. For instance, the last time Venus occulted Mars was on October 13, 1590, and the next time will be June 4, 2327.

This image is an awesome-almost-occultation!

Thanks Indigo – it's funny that the article mentions the "dark side" of the moon; meaning the side opposite the bright crescent. Which brings up another phenomenon - that the bright crescent appears larger, out of proportion, to the rest of the moon? My wife commented on it the other night. It's more apparent "live" but some photos also seem to appear that way. Wonder why?

Moon Crescent.jpg (2.13 KiB) Viewed 251806 times

[Boomer12k]

An amorous rendezvous to be sure.…..

:---[===] *

[FloridaMike]

The dark side? What's that?

It can only be seen from the dark continent....

[Ron-Astro Pharmacist]

The dark side? What's that?

It can only be seen from the dark continent....

And "if seen" suddenly from Earth is liable to leave one "in-continent". Yes - probably the dark version.

[TonyT]

No chance this will happen again, she'll be long dead. I doubt whether she has another title left in her...

[philhart]

Would love to see a link to Kevin Bourque webpage with exposure details for this. A search doesn't reveal anything obvious?

Lovely image!

[Nitpicker]

To pick a nit, why say "digital camera" instead of "camera"? Digital is default today.

Habit by those who grew up with film? I prefer "electronic camera" since the sensors which have replaced film are fundamentally analog devices, not digital ones.

Electronics can be analog or digital. (I used to own an electronic film camera.) The kind of image produced by a "digital" camera is a "digital image". Other names with more or less the same meaning are "raster image" or "bitmap image". They are all images formed by a 2-D array of pixels, rather than a light sensitive photographic emulsion.

Clutching at straws, perhaps the use of the term "digital camera", rather than just "camera", also implies a certain level of image processing and/or computing capability.

[rstevenson]

Electronics can be analog or digital. (I used to own an electronic film camera.) The kind of image produced by a "digital" camera is a "digital image". Other names with more or less the same meaning are "raster image" or "bitmap image". They are all images formed by a 2-D array of pixels, rather than a light sensitive photographic emulsion.

I think you'd have to add to your definition, nit, that the array of pixels be regular. After all, those tiny crumbs of silver in film emulsions are discrete bits themselves, just not very regularly arrayed. (I seem to recall that one innovation, perhaps in the 70s, was to get the silver grains to spread more evenly and to lie flatter, resulting in a faster, more fine-grained appearing film.)

Rob

[floyd51]

I'm familiar with diffraction spikes, but why does Venus have eighteen of them?

The wide field, about eleven full moons, suggests the photograph was "camera only", no telescope.

[Chris Peterson]

I'm familiar with diffraction spikes, but why does Venus have eighteen of them?

The wide field, about eleven full moons, suggests the photograph was "camera only", no telescope.

Because the lens had a 9-leaf iris.

[Nitpicker]

Electronics can be analog or digital. (I used to own an electronic film camera.) The kind of image produced by a "digital" camera is a "digital image". Other names with more or less the same meaning are "raster image" or "bitmap image". They are all images formed by a 2-D array of pixels, rather than a light sensitive photographic emulsion.

I think you'd have to add to your definition, nit, that the array of pixels be regular. After all, those tiny crumbs of silver in film emulsions are discrete bits themselves, just not very regularly arrayed. (I seem to recall that one innovation, perhaps in the 70s, was to get the silver grains to spread more evenly and to lie flatter, resulting in a faster, more fine-grained appearing film.)

Rob

Whilst the pixels are normally arranged in a regular fashion (which is all but implied in the word "array"), the more important difference is that the pixels are all individually addressable.

[Chris Peterson]

Whilst the pixels are normally arranged in a regular fashion (which is all but implied in the word "array"), the more important difference is that the pixels are all individually addressable.

Even more important is that there actually are pixels. Film grains are not even close to being the equivalent of pixels. They are binary, and respond to light in clusters. The result is that film has fairly poor resolution, and worse, has a MTF that is highly dependent on contrast. CCDs and other electronic sensors have pixels that are independent of each other, so their frequency response is independent of contrast.

(Very few electronic sensors have individually addressable pixels... but perhaps you meant something different by that terminology.)

[Nitpicker]

Whilst the pixels are normally arranged in a regular fashion (which is all but implied in the word "array"), the more important difference is that the pixels are all individually addressable.

Even more important is that there actually are pixels. Film grains are not even close to being the equivalent of pixels. They are binary, and respond to light in clusters. The result is that film has fairly poor resolution, and worse, has a MTF that is highly dependent on contrast. CCDs and other electronic sensors have pixels that are independent of each other, so their frequency response is independent of contrast.

(Very few electronic sensors have individually addressable pixels... but perhaps you meant something different by that terminology.)

All I really meant was that the value recorded by each pixel on a digital image sensor, can be converted from an analog signal, to a digital value, and stored in the digital computer memory on board the camera.

[Chris Peterson]

(Very few electronic sensors have individually addressable pixels... but perhaps you meant something different by that terminology.)

All I really meant was that the value recorded by each pixel on a digital image sensor, can be converted from an analog signal, to a digital value, and stored in the digital computer memory on board the camera.

I suspected something like that. Of course, this is analogous in many ways to digitally scanned film.

[Nitpicker]

(Very few electronic sensors have individually addressable pixels... but perhaps you meant something different by that terminology.)

All I really meant was that the value recorded by each pixel on a digital image sensor, can be converted from an analog signal, to a digital value, and stored in the digital computer memory on board the camera.

I suspected something like that. Of course, this is analogous in many ways to digitally scanned film.

But without all the time, fuss and expense of the chemistry (and yes, with improved resolution, etc, too).

[MarkBour]

. . . Which brings up another phenomenon - that the bright crescent appears larger, out of proportion, to the rest of the moon? My wife commented on it the other night. It's more apparent "live" but some photos also seem to appear that way. Wonder why?

There is the following : http://blog.pnas.org/?p=1484
In the article, neurologist Jens Kremkow describes it as an illusion that has an explanation in the neurons in the retina.

I'm not at all sure it's the only thing going on, though. It could well be that some cameras are also "spreading the light" in some circumstances.