The Athenaeum

"Visual Observations" John Minnerath

This is very pretty.  It may require you to download a converter program from the Microsoft site in order to be able to open it.  It would be well worth the effort.  pl

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Prairie Skies, Part 2

The bad news for severe weather geeks like me is that not every night can have a thunderstorm.  So we need to find things to look at in the sky when there's no clouds or lightning to capture our attention.

Truth be told, I was an astronomy geek long before I became a weather geek, but my interest in astronomical observing tended to be visual.  I had spent vast amounts of my youth connecting various cameras to my supply of telescopes, but the results tended towards blurry images and long waits at the photo developers to see what I'd done wrong a week earlier.

But last Christmas, my son talked me into buying a T-adapter to connect his Nikon DSLR to one of my telescopes.  And since then, we've been hooked on astrophotography.  And it turns out that taking good pictures of celestial objects is easier than one might think, once a few basic principles of "what is signal?" and "what is noise?" are understood.  And once we understood these, our photography efforts improved greatly, as the following image shows.

That image is of M31, the Andromeda Galaxy.  It was taken with a box-stock bottom-of-the-line Canon digital camera (the 1000D), through a small telescope (an AstroTech AT66) that really isn't much more in terms of its optics than half of a pair of really good binoculars.  The mount used to guide the telescope can be described as "hopelessly inadequate for the job", yet the picture's quality speaks for itself.  So how did we get such a fine image from such simple equipment?

As SST/TA's resident Nassim Nicholas Taleb fan, I tend to think of this question in terms of Taleb's dichotomy of mediocristan and extremistan.  Mediocristan is the world of statistical variation we are used to, where distributions of such parameters as height and IQ live.  Variations in this world are captured reasonably well by Gaussian (i.e., bell-shaped) probability curves, with symmetrical statistical distributions about some easy-to-determine mean (average) value.

Extremistan is where we find those low-probability/high impact entities that Taleb calls Black Swans.  This parcel of intellectual real estate is characterized by wildly different characteristics from the norm, so that terms like "average" don't help much in understanding overall tendencies, and where much of the domain of interest is as interesting as watching paint dry, so that only rarely are truly spectacular results found.

Here's a good example of how these astronomical prizes are found: this image is taken in the direction of the heart of our galaxy, and two especially interesting objects pop up there, the Lagoon Nebula in the south (down) and the Trifid nebula to the north (up).  Note that there's lots of celestial real estate that's full of stars, but that the bright nebula are rarer in this view, even though this direction for our observation is about as rich an area as we'll find at this end of the universe.

And it turns out that this is a pretty good approximation for looking at the night sky.  If you get out under a good dark sky far from any city lights, and examine the heavens with a substantial pair of binoculars, you'll soon find that most of the sky is populated with just a bunch of relatively nondescript stars, but some of it has some more interesting features, e.g., where the Milky Way traces the shape of our own galaxy.  And if you use more powerful optical aid, then you'll soon learn that just pointing a big telescope at random generally leads to small fields of view that have some stars in them, but nothing all that interesting.

The key word in that last sentence is "generally".  Because if you know where to look, then amazing things can be found, e.g., galaxies, nebula, clusters and such.  These sights are rarer, and their signals do not lie in mediocristan, but live squarely in extremistan, because they run the gamut from small clusters of like-minded stars, to the remnants left over from supernova explosions, to stellar nurseries where new suns are being born, to clusters of galaxies that defy comprehension in their sheer scale.

But the problem is noise... because whether you're looking at these extremistanistic signals or taking pictures of them with expensive imaging equipment, there's noise found in the optical train, either in your own eye (which is notoriously noisy in the dark) or in your camera.  And this noise makes detection of the beautiful signals difficult or impossible.

Luckily for the astronomy geek, the laws of statistics can be used to fix this problem, so that we can use low-cost optical and camera equipment to gain high-value images of celestial objects.  The key is appreciating that noise lives in mediocristan, and in particular, it has a statistical distribution that has mean zero, and that is essentially Gaussian.   What this means to us is that if we take a whole bunch of images of the same object, and then average them, the signal persists while the noise dissipates.

And then we get better results than we deserve.

Here's an example, taken at 4 am last week, just as the winter constellation of Orion was rising right before sunrise.  This first image is a 30-second exposure at high gain from my Canon XS camera taken through an old-school Celestron Schmidt-Cassegrain telescope, and we can see that something interesting is going on here, but exactly what is not yet obvious.

The compound stellar system known as Trapezium is visible near the center of the nebula, and there are hints of interesting color appearing in the frame, but we really can't see much of anything in particular.  But if we crank up the gain in the image, more hints appear of structure and color, but unfortunately, they appear along with an awful lot of noise, as the next image shows.

This is an improvement in terms of seeing the bigger picture of this nebula, but we can do better by taking more exposures, and then adding them up and dividing by the number of exposures, so that the signal persists, but the noise tends towards its average value of zero.  Then we can easily see the structure of the Great Nebula in Orion emerge in the next image of this sequence:

So the key here is to stack up a sequence of not-so-interesting noisy images, so that we can extract a single relatively noise-free picture by taking advantage of the fact that what we seek is found in Extremistan, and what we wish to disappear lives in Mediocristan.  Thanks to that simple fact, we can readily keep what we want and lose what we don't.

And this statistical magic is not confined to big bright objects like the Orion Nebula.  Here's the same result applied to a dim object that barely registers in any individual frame.  This example here is NGC 891 (NGC = New Galactic Catalogue), an edge-on spiral galaxy at the edge of the constellation Andromeda.  The individual images barely register anything beyond a fairly-barren star field, even with a 30-second exposure at high gain through a good-sized telescope:

As always in astronomy, success lies in knowing just where to look, and in the center of this individual frame is a ghostly little needle-shaped apparition better known as NGC891.  If we crank up the gain in this image, we begin to see the shape of this galaxy, but we also see a whole lot of noise:

And if we stack a bunch of these images (in this case, 20 of them, for a total of 10 minutes of exposure), then we begin to get somewhere, and the shape of an entire galaxy emerges for our consideration:

This technique of getting better images than we deserve can be utilized on just about anything found up there, and planets are especially good targets for this imaging method.  In this case, we don't try to save up a lot of photons via a small set of long exposures, because solar system objects are pretty bright.  Instead, we take a ton of short exposures by making a movie of the object, and then working our averaging technique over hundreds or thousands of very-short-duration frames.

Here's an image of Jupiter taken last week.  Not much to see here beyond a Jovian disk suffering from a lot of noise and distortion introduced by the earth's atmosphere... 

But if we stack up about 500 of the clearest frames from a movie of Jupiter taken through the telescope's optical train, a much clearer picture of this fascinating planet emerges:

You gotta love that Great Red Spot, now that you can see it!

Armed with this technique, almost any modern telescope can be connected to the simplest digital single-lens-reflex camera, and the result is remarkable given the simplicity of the equipment involved.  And while it helps to have a good equatorial mount for tracking the stars, even the simplest clock-driven alt-azimuth mounts found on entry-level telescopes can be effectively utilized for astrophotography by taking account of the field rotation that occurs with time, so that the averaging process just requires a tad more alignment work in order to gain the best images.

So thanks to good optics and modern digital camera technology, you too can be an astrophotographer.  All it takes is knowing where in Extremistan the interesting objects are to be found, and then using the Mediocristan residence of the camera noise to improve the signal while getting rid of the noise.

--Cieran

Was the Civil War necessary?

Robert Kagan has an oped piece in the Washington Post today on the subject of the categorization of wars as "necessary" or of "choice."  He is correct in thinking that this is rhetorical trivia.  He is correct n writing that nearly all wars represent choice.  After all, surrender is always a possibility.

In the course of his essay he writes -

"There have been few if any clear-cut wars of necessity in America's history. Not the Revolution, where both the colonists and the British had other and, in the British case, better choices. Not the Civil War, which some historians still believe was an unnecessary and catastrophic spilling of American blood. (Slavery, they wrongly argue, would eventually have died of natural causes.) And never mind the war with Mexico, the Spanish-American War, the many interventions in Central America and the Caribbean, or, in the view of many, World War I. "

Kagan's essential argument seems to be that the essential question is not whether or not wars were "necessary" but if they were a good idea.

"They wrongly argue?"  Sorry, but I think the word "wrongly" in this sentence is merely the product of the "received wisdom" passed down to and among the physical and/or spiritual descendants of the winning side.  The carnage of the Civil War and the devastated and impoverished lives of all the people of the American South necessitated a life there of diminished chances and opportunities that lasted a hundred years.  The demographic and economic wreckage in the South and the human losses in the North were so bad that a compelling argument had to be made that the moral imperative of the evil of slavery in the South had made this awful war an "irrepressible conflict."  The eternal and immutable nature of slavery as an institution in the south served that pupose well and still does.  The fact that nearly all the Northern states had at one time or another had been "slave" states seems to mean nothing to that propaganda theme.

Just for the sake of argument imagine that the seceded states had decided in 1861 (the year the war began) to collectively abolish slavery.  Would the North (the United States) have then allowed those states to depart from the union in peace?  If the answer is no, then slavery in the South was not the primary cause of the war. 

Nevertheless, Kagan chooses to characterize the cause of the war as slavery, and to imply that this moral evil could only have been expunged by mass violence.   Is that true?  Agribusiness in the South based on slave labor was quite profitable.  Agribusiness in Brazil based on slavery was also quite profitable.  Slavery in Brazil was abolished in the late nineteenth century on the basis of gradual compensated emancipation.

Slavery was an institution inconsistent with American political ideals and the developing collective consciousness of the Western world.  Economic determinists will argue that profits in business would have "trumped" any argument from "higher values" for a gradual emancipation in the South.  People who think that clearly believe that Southerners were simply evil, that they enjoyed the sadistic perquisites of domination of another people so much that the disapproval of all of Western civilization would not have moved them to free the blacks.  Is that true?  Try to imagine an alternative 1900 or 1950 in which millions of African-Americans would still have been held in conditions of chattel slavery.  Can you do that?  If you can't, then perhaps there is something wrongly argued in Kagan's statement.

This brings me to my point.  If Kagan's argument in his oped hinges on the centrality of judgment and wisdom in deciding on war or peace, and he believes that the American Civil War was an inevitable, indeed a desirable thing, then why should we accept his judgment about the virtue of wars like Iraq and Afghanistan?  pl

 

Mesothelioma, asbestos and the military

I have been asked to post this article concerning the danger of mesothelioma in the armed services and I happy to do so.  pl

Download Mesothelioma

Prairie Skies, Part 1

One of the best things about living in flyover country is that all that open space makes for plenty of open skies.  And here where warm moisture from the Gulf of Mexico collides with cold dry air from the Rockies, there are plenty of interesting events staged in those wall-to-wall skies.

From the front porch here, we've had an up-close-and-personal view of two tornados rolling through in the last few months (thankfully with no loss of life and only minimal property damage)... and countless thunderstorms that shake the foundation of the house long before you can hear them coming, and that light up the night sky even when they are over a hundred miles away.

Sometimes, all one has to do to capture images of these nighttime noisemakers is to (a) put the camera on a tripod, (b) set the gain low enough to permit an exposure of several seconds in duration, (c) find a good focus, and (d) start taking pictures.

Here's some images taken from the front porch of last week's storm.  Enjoy!

--Cieran