Michael A. Covington    Michael A. Covington, Ph.D.
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Popular topics on this page:
What color is that dress?
The economy today
Confessions of Valwood's first computer geek
Valdosta corrects an architectural blunder
The oldest building in Valdosta
The horrible false positive AIDS test
The Art of Electronics 3 is here
FireCapture goes to 60 fps and hangs at odd moments
Astrophotography exposure calculator
Deconvolution works!
Moon, mini- and super-
Moon (Mare Crisium)
Moon (with isolated point of light)
M46 (star cluster with nebula)
M47 (star cluster)
M65 (galaxy)
M65 and M66 (galaxies)
Nova Sagittarii 2015 No. 2
Nova Sagittarii 2015 No. 2
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AoE 3 is here

"More here than y'all can shake a stick at," as they'd say in New Orleans. I'll close out March with an exceptionally long set of Notebook entries, plus promises of more!

The long-awaited third edition of The Art of Electronics is finally here. I say long-awaited because it was initially scheduled to be published 20 years ago.

And, to my considerable delight, it contains not only my name (in the acknowledgments) but also a link to this blog, specifically to this amusing item, which is not just for electronics buffs.

This may be one of the two most important electronics design books of the twentieth century (the other being the much earlier Radiotron Designer's Handbook). It is extremely practical, dipping into theory to explain practice rather than the other way around. Very sensibly, the authors do not try to build mathematical models more precise than the numbers on which they are based. For example, if you only know that the hfe of a transistor is somewhere between 30 and 200, you probably don't need to model its behavior with a precise cubic equation. Instead, you need to design a circuit that makes the transistor behave as desired regardless of variation of its parameters.

The new edition is 1100 pages long and includes single-board computers and microcontrollers, with a tip of the hat to Arduino and even Adafruit. The authors point out that laboratory and experimental electronics is closely tied to hobby electronics — both involve building one-of-a-kind gadgets and refining the design as you go.

As a hobbyist who sometimes strays into the professional practice of circuit design, I had a (minor) (almost) life-changing experience when I found the first edition at the Cal Tech bookstore in 1982 — and, as a newlywed, couldn't afford it — so I earned a copy by doing some reviewing for the publisher, and then waited eagerly for weeks for the book to arrive. (As I recall, the book I reviewed was Wallis and Provin's Manual of Advanced Celestial Photography, another classic.) At last, The Art of Electronics was an up-to-date book that would actually tell me useful things, not just theory, and would tell me things I didn't already know. At the time I was learning analog electronics from the National Semiconductor Linear Databook. All the other practical books were too superficial, and the theoretical books were too impractical.

Of course, I got the second edition as soon as it came out (1989?) and passed along my first edition to a student down in Valdosta. Now I have the third edition, but my second edition is going to stay. I might even track down a used copy of the first.

FireCapture goes to 60 fps and hangs whenever you touch the exposure settings

I highly recommend FireCapture, free software for capturing astronomical images with a video camera. But when I was using it with my ImagingSource DMK camera last night, I had a problem: Every time I touched the exposure settings, the frame rate went to 60 fps and the camera hung.

My USB connection apparently doesn't work faster than 30 fps with this camera.

Note: The hanging was caused by a failing USB cable. With a new cable, it disappeared. This was not really a software problem. But in case you encounter a hardware problem similar to mine and harder to fix, read on.

But why did the rate keep switching? Because FireCapture was trying to use the highest rate compatible with the exposure time. (My exposure was usually less than 1/60 second.)

The cure? Edit the file FireCapture.ini (in the same folder as the executable file) and set syncFPS=false.

Now you have to be careful not to use a frame rate too fast for your exposure time. If you do, I imagine you will get duplicated frames — at least, that's how most video software does it.

Another hint: With a color camera, turn on DeBayer for focusing, but then turn it off for recording. The files will be 1/3 as big (important) and you can decode the color with FireCapture's (separate but included) DeBayer program.

Astrophotography exposure calculator

Want an astrophotography exposure calculator? You can still use the one I wrote fifteen years ago, which you can download from my rather old astronomy software page.

It's called ASTREXP.EXE and was written in Delphi. One day I'll rewrite it in Java or C#. In the meantime, here's what it looks like:

It covers brightnesses all the way from distant galaxies to the surface of the sun, using real astrophysical units (magnitude per square arc-second). Some hints for using it in modern times:

  • Set the reciprocity exponent to 1.0 for any kind of digital imaging.
  • For the "film speed" use the ISO setting of the camera; for CCD cameras, if unknown, guess 1600.
  • Under Windows 8 you will have to right-click and "unblock" the .exe file in order for it to run.

As you can see, the program says that with my DSLR, I can photograph M57 in 30 seconds with my f/10 telescope. And I can, and I did. (If you click, you'll see a stack of many 30-second exposures, but even a single one shows the nebula well.)


Deconvolution works!

This is not a great picture of the galaxy M65. In fact, it is the very first one I took while trying out my new guidescope with the autoguider. It's a stack of five 2-minute exposures at the f/10 Cassegrain focus of my 8-inch telescope, with the gibbous moon close to the galaxy in the sky.

As you might guess, I didn't have the guidescope and autoguider as tightly secured as I should have, and the tracking was poor. (More about that later; there's an interesting story to tell.)

But I was able to fix the bad tracking with Richardson-Lucy deconvolution. The mathematical principle is that if you know exactly what has happened to an image, and if you know some underlying properties of the image so that you don't make excessively wild guesses, then you can undo the damage.

In this case I needed to convert elliptical star images (originally about 3×5 arc-seconds) into round ones. In PixInsight that's easy. Just choose "motion blur deconvolution" and put in an indication of how much the image was smeared (or do it by trial and error), and out comes an image with nice round star images, and with additional detail in the galaxy itself.

Here are highly magnified "before" and "after" pictures.

Caveat: This works only if the stars are just slightly elongated. If you have a severe tracking problem, you're still on your own.

That's enough for today. More pictures tomorrow!


Nova Sagittarii again

Here's a better view of Nova Sagittarii over the skyglow of Watkinsville, Georgia. The nova has brightened to magnitude 5.2 or so. Single 30-second exposure, Canon 60Da at ISO 1600, Sigma 50/2.8 lens at f/4, iOptron SkyTracker, Photoshop.

This was taken around 6 a.m. today (March 28).


Dr. Mlodinow's horrifying false positive AIDS test

Physicist Leonard Mlodinow had a horrible experience recently because his doctor misunderstood a point of mathematics, or maybe common sense.

For insurance reasons, he was tested for HIV, the virus that causes AIDS.

The test came back positive, and since it is wrong only 1 time in 1000, he doctor told him that with 999/1000 certainty, he had HIV and was going to die of AIDS.

Wrong. That reasoning ignores an important fact: In Dr. Mlodinow's segment of the population (no history of possible exposure, no symptoms, and an ethnic group in which AIDS is uncommon), the chance of having HIV is less than 1 in 10,000, maybe a lot less.

So, even without any fancy mathematics, you can see that a false positive is much more likely than a true positive because the disease is, under the circumstances, so rare. False positives are rare, but real HIV is even rarer.

The doctor failed to see that the chance of A given B is not the same as the chance of B given A. (That's Bayes' Theorem.) Instead of asking the chance that Dr. Mlodinow had HIV given the test result, he was asking the chance of the test result being wrong if Dr. Mlodinow had HIV. Not the same thing!

You don't have to know much mathematics to appreciate this. All you need is to know that "most fire trucks are red" is not the same as "most red things are fire trucks."

Getting back to medical tests, the lesson is, if a condition is unlikely in the first place (an uncommon condition, no symptoms, low risk factors), then a positive test result is more likely to be false. Don't make a big decision based on a single test. Follow it up. Look for more evidence.

Doctors are starting to talk about the problem of overdiagnosis (too much labeling and treatment of people whose conditions don't warrant it) and there's even the slang word "incidentaloma", which means something that looks like cancer on some test but does not need treatment.

In the world of jurisprudence, it's very important not to punish people for a single failed drug test in the absence of other indications of drug use. If you do, you will definitely punish some people who don't deserve it, and these may be more numerous than the ones who do deserve it!


Two short observations

(1) There is a sense in which I don't want to be a "freethinker." I want to remain fettered by logic and facts.

(2) Postmodernism, a.k.a. relativism, the belief that there are no objective facts, is traditionally associated with the fashionable left wing. We have expected conservative politics to be associated with conservative epistemology — respect for facts and existing expertise.

But lately I am seeing alarming signs that too much the political right wing does not believe in objective facts.

People don't want information; they just want to keep rooting for the same side as their friends.

And, to an alarming extent, "I have a right to continue being an ignorant hick" has become a theme in our popular culture.


Jupiter, done right

Finally, some steady air and a really good image of Jupiter. You can see the Great Red Spot coming around the edge at the lower left.

This was taken last night (March 23, 10:12 p.m. EDT). 8-inch EdgeHD telescope, 3× Barlow, DFK camera, stack of the best 75% of about 3600 video frames, enlarged 1.5× during stacking with AutoStakkert, enhanced with RegiStax (although the un-enhanced image was already surprisingly good).

I finally remembered one of my techniques from last year: record the file un-deBayered (with color not decoded), then deBayer it with the FireCapture utility afterward. This gives higher-quality deBayerization and, more importantly, makes the video files only 1/3 as large, much easier to transfer from computer to computer and to archive.

One point of light

The bright spot that you see at the top isn't a star — it's an isolated mountain peak catching sunlight before the surrounding area does.

Taken with Canon 300-mm f/4 lens and 1.4× converter on a fixed tripod. For dynamic range, exposures of 1/10, 1/20, and 1/80 second were stacked (all at f/11, ISO 640) after aligning them by hand in Photoshop. Canon 60Da camera.

Impressions of the Orion ShortTube 80

Last night (March 23) was my first astronomy session with the new Orion ShortTube 80 telescope, which I can mount on a tripod by itself or piggy-back on my 8-inch. Impressions:

  • This is not a lunar and planetary telescope. There is noticeable chromatic aberration even at 25×. The view of the moon was actually sharper with the telescope stopped down to f/11 using the central hole in the lens cap.
  • Eyepieces make a difference. Good Orthoscopic and Plössl eyepieces give better views than simpler eyepieces and those of uncertain type.
  • It's a handy super-finder. When I was photographing Jupiter, it was very handy to put a crosshairs eyepiece into the piggybacked ShortTube and use it to help aim the telescope. The DFK camera has such a narrow field that it's easy to lose track of where Jupiter is; the telescope shifts a little as the weight on it is changed, and a movement of just 1 arc-minute can put Jupiter outside the field altogether. (A flip mirror in front of the DFK camera would solve this problem even more elegantly; I may try that.)
  • At a dark site, it would be a fine deep-sky telescope. The view of bright star clusters at 15× in the "super-finder" was a good complement to the view at 100× in the telescope. Under dark skies, the ShortTube should show all the Messier objects. In town, it was only useful for the brightest ones.
  • Probably not a photographic instrument, except for experiments. I'll try photographing some deep-sky objects with it to see what I get, but I don't expect the images to be as good as with my Canon 300-mm f/4 lens. Still, they might be entirely good enough to intrigue a beginner and to produce pleasing pictures. I'll see what I get.

Nova Sagittarii while it's still there

Nova Sagittarii 2015 No. 2 peaked at magnitude 4.5 (easy naked-eye visibility) about two days ago, but it was raining here. This morning (March 24) I was up bright and early (well, dark and early) at 5:30 to photograph the nova before it fades from visibility. Here it is:

test image

The nova is right in the middle of the "teapot" asterism, which fills the picture (along with trees). Single 15-second exposure, Canon 60Da, ISO 1600, 50-mm lens at f/4 on iOptron SkyTracker.


A telescope for my telescope

I've bought a telescope for my telescope. This Orion ShortTube 80 refractor will ride piggyback on my 8-inch and serve as a guidescope, high-magnification finder (for centering planet images on the DFK camera sensor), and wide-field auxiliary telescope (for faint nebulae).

Here you see it on a wooden dovetail block that I made for two purposes. Thanks to a threaded insert in the bottom, this dovetail block enables me to put the ShortTube (by itself) on a camera tripod. The rest of the time, it gives me something to clamp the rings to when the ShortTube isn't mounted on the 8-inch.

Wooden dovetail blocks are easy to make with a table saw. The specifications for a Vixen dovetail are: 43 mm wide on the wide side, 12-degree slope to the edges, and no particular thickness (1 to 2 cm will do). Wooden components probably aren't stiff enough for critical astrophotography, but they are fine for visual setups and for prototyping setups you will make (or have someone make) out of metal.

I haven't tried this telescope on the stars yet. Judging from a casual look at some distant trees, it's going to have some visible chromatic aberration, as one would expect from an economy-priced f/5 refractor. Interestingly, the lens cap has a hole with a second cap, making it easy to use the telescope at f/11 (45 mm aperture). I might use it that way for full-face moon shots.

Photo with my vintage 2004 Canon Digital Rebel (300D), which works as well as it ever did, and is fine for illustrations where the end result will be much less than its eight megapixels.


A flurry of astrophotography

We are suddenly having warm, partly clear weather, and I jumped at the chance to do some astrophotography on the nights of March 15 and 16. The pictures of star clusters and galaxies were just casual experiments, to scout out the objects for better photography later, so I took lots of shortcuts; dark-frame subtraction was done in the camera, exposures were short, I tried many different ways of adjusting the autoguider, and I used the wrong kind of focal reducer (because I haven't bought the right kind yet). Nonetheless, I got pictures!


8-inch EdgeHD telescope, 3x Barlow lens, DFK camera, stack of the best 75% of about 3600 video frames; Autostakkert, RegiStax, Photoshop.

M46 (star cluster with planetary nebula)

It is debated whether the nebula (the little doughnut in the picture) is part of the star cluster M46, or is in front of it, or is beyond it.

This is a stack of 17 (yes, 17) 30-second exposures taken with an EdgeHD 8-inch telescope and a conventional Celestron focal reducer (designed for Schmidt-Cassegrain telescopes, not EdgeHD, and hence not giving sharp images all the way to the corners). The upper picture shows you the central region of the picture, and the lower one is uncropped. Canon 60Da camera, ISO 3200; Deep Sky Stacker and PixInsight.

M47 (star cluster)

Like the pictures of M46 above, but this is a different star cluster and only 13 exposures were stacked. In the wider-field picture you can see another distant star cluster at the lower left. Image quality near the edges is reduced because I was using a focal reducer designed for Schmidt-Cassegrain telescopes, but this telescope is an EdgeHD.

M65 and M66 (galaxies)

I didn't expect to get much here, but you can see two galaxies. M65 is the one nearer the center. This is a stack of nine exposures. Just as in the pictures above, image quality near the edges is reduced because I was using a focal reducer designed for Schmidt-Cassegrain telescopes, but this telescope is an EdgeHD.



24 hours in Valdosta — part 5:
Dinner, Action Trav'lers, and heading home

So far I've only described my first two hours in Valdosta. I need to wrap up the rest of the trip quickly so I can get on to blogging other things.

Although I don't normally mention people by name here unless they are already in the public eye, I want to make an exception and name the friends I saw on the trip, some of whom I hadn't seen since high school (1973!). Imagine you're reading the society column of the Daily Notebook.

After my walk around historic Valdosta, I headed for a prearranged dinner meeting at El Toreo, my favorite local Mexican restaurant, near Valdosta Mall. I didn't know exactly who was coming. We had organized it on Facebook.

Present were Susan Davis, Jan Powell (daughter of one of Valdosta's legendary teachers), Lucian Holtzendorff, Robert Winter, Ken Klanicki, Susan Gish Smith, and Mercer Sherman (Valwood 1976 or so) and his wife and daughter. We also had a brief visit from Pam Bazemore and from Kathy Willis (sorry, I didn't catch their married surnames). As they say, "A good time was had by all."

The next day I went to a business meeting that was the real purpose of the trip, but must remain forever shrouded under nondisclosure.

Then I visited with Robert Winter and Lucian Holtzendorff at Alert-Tech Systems. Back in the 1970s, Robert and Lucian were prime movers behind Adventuretours (The Action Trav'lers), a remarkable youth travel club with which I traveled to Mexico and other places. In the 1980s and 1990s the club transmuted into an international exchange program for high school students, but it never died out. And I have a big announcement: The Action Trav'lers will ride again as a travel club for mature adults (mainly its own alumni!). They've been given a luxurious diesel bus which will be even more luxurious after they do the traditional Action Trav'lers conversion for camping. But the new club will not necessarily camp — given our age, I've been told that four-star hotels are not out of the question.

Last, I stopped for lunch at a Subway sandwich shop across the street from the late lamented Bynum's Diner. There I ran into one more old friend — high-school classmate Conner Thomson, who had just moved back to Valdosta after years in Gwinnett County. I've begun to suspect that you can find the Valdostans who have been in North Georgia because they eat at Subway and Atlanta Bread Company.

Northward through the Cook County Billboard Preserve, and back to Athens in time for a late dinner with Melody at Mirko in Watkinsville... home again, with promises not to stay away seven years before visiting again!


24 hours in Valdosta — part 4:
The oldest building in Valdosta

In all these years I had never taken a look at the oldest building in Valdosta (or at least the oldest church building — there may be a house about the same age), and until recently I didn't even know about it. It's the original First Baptist Church, on East Central Avenue, now occupied by a Pentecostal church. (By the way, its second occupant, a Primitive Baptist church, is a name that may need explaining. Primitive Baptists are numerous in south Georgia; they try to run a church more like the first century that other Baptists, hence the name.)


24 hours in Valdosta — part 3:
Valdosta corrects an architectural blunder

After getting my car out of the VSU time-limited parking space (see yesterday), I went for a walk downtown and was pleasantly surprised to find that Valdosta has seen the error of its ways. A serious architectural mistake from 1962 is being corrected.

Valdosta has a beautiful Greek Revival courthouse built in 1903-1904. Back in 1962, a shoebox-like addition was built onto the north side of it (click here for a picture). I set foot in the shoebox only once, in 2007, and found it surprisingly small.

Ugly box-like additions to elegant older buildings were a 1960s and 1970s fad. The University of Georgia suffers from several of them (e.g., Park Hall). I have heard the fad traced to the Bauhaus architectural movement, but let's be clear: I don't object to modern architecture. What I object to is the arrogant modernist notion that you can no longer build anything traditional-looking, even when needed to harmonize with its surroundings.

Now the shoebox has been torn down. The functions of the courthouse have been transferred to a majestic red brick building a couple of blocks north, and the historic courthouse is being remodeled. I look forward to seeing it when it's finished.


24 hours in Valdosta — part 2:
A hero's welcome in Nevins Hall

On reaching Valdosta, I had some time to kill, so I decided to go to Valdosta State University, and specifically Nevins Hall, to see if anyone I knew was still there.

I should explain what Nevins Hall means to me. That is where, in 1968, my interest in astronomy was fed by a class trip to the planetarium. That is where the local astronomy club met. There, in 1969 and 1970, a physics faculty member, Edward Van Peenen, let me use labs and even the observatory under his supervision. There, in 1973, L. R. Howell taught a computer programming course and I got my first taste of computer programming. In short, Nevins Hall was my very first contact with higher education.

There were people I knew in Nevins Hall. They hadn't been there since my student days, of course; they're astronomers that I met in the 1980s while keeping in touch with VSU. Specifically, I found Kenneth Rumstay and Martha Leake in their offices, and to my surprise, they gave me what amounted to a hero's welcome.

I had parked my car in a 45-minute free-parking space. (Clever idea: five minutes too short for a class period, so students can't park there for classes, so the parking spaces remain free for people on short errands.) In less than 45 minutes, I visited with both astronomers; was shown the observatory with its new (10-year-old) DFM telescope, which I was invited to come and use; was invited to give a short talk to the Society of Physics Students; and did so. It was a very short talk because my 45 minutes were nearly up. I told them that their training in physics and astronomy would equip them to apply mathematics in ways they had not yet thought of, and they should look at "big data" and artificial intelligence.

After dinner I came back to the campus. Seeing activity around the observatory, I thought about going up there but decided not to disturb them — thought that if it wasn't somebody I knew, I might not be very welcome. In fact, I found out later that it was Dr. Rumstay and some of the students I had already met. I should have gone.

But instead I went into the Odum Library. This library, in its earlier location (Powell Hall), was the first academic library I ever used, starting back in 1969 (seventh grade). Roaming around the modern, very brightly-lit building, I found several books that were old friends, including The Flammarion Book of Astronomy and Celestial Objects for Common Telescopes (in which there were some date stamps, from February 1971, that were surely mine).

I think I'm going to take them up on the invitation to come and use the telescope and teach people how to do astrophotography with it. It is a DFM 16-inch classical Cassegrain on a fork mount with a very good computerized drive. The previous telescope was a 16-inch Cassegrain on a German equatorial mount; I went to its dedication in 1986. The original telescope, which I occasionally used as a student, was a 12.5-inch Optical Craftsmen Cassegrain/Newtonian. I am told that both of the older telescopes are in storage. I rather hope they eventually built an observing station out in the country and put at least one of them into service.


24 hours in Valdosta — part 1

I spent the past two days making a quick trip to my home town, Valdosta, Georgia, because of a brief business obligation. At the last minute Melody opted not to come along, not because of any serious problems, but just because something had come up. So she was there at least potentially. Until recently we were not very able to travel because of her hip problems; in fact our last trip to Valdosta had been in 2007. That makes this the longest lapse ever between my visits to my native land (South Georgia).

Getting there was half the fun. I drove the same route through Macon as many times before, but the speed limits on I-75 are higher now. Someone south of Cordele flies a Confederate flag. Someone else has a billboard that says "Secede!" with a web address. South Georgia is definitely more southern than North Georgia. Either that, or some people live backward through time, like Merlin, and have just reached the 1860s.

I drove through the memorable Cook County Billboard Preserve, where herds of wild billboards still roam the plains the way they did everywhere 50 years ago. Foregoing Magnolia Plantation, Plantation House, and Stuckey's, I completed the trip without visiting a single tourist trap or buying any gooey candy.

Then I got to Lowndes County. Quoting Sir Walter Scott ("This is my own, my native land!") I drove into town and suddenly was reminded that South Georgia has a scent. It's more noticeable now that most air, even outdoors, is smoke-free. But it is mainly present in the water, which is slightly sulfur-flavored and which I call Acqua Minerale di Valdosta. Not having tasted it for seven years, I did not find it entirely unpleasant when I first visited a water fountain; it's even vaguely sweet; but one can get tired of it. Or, I suppose, put it in green bottles and sell it to Italians. Or both.

My room at the Hilton Garden Inn was on the third floor, and because the terrain is so flat, I expected to be able to see a long way. As it happened, the room commanded an excellent view of two other hotels.

More about the trip tomorrow.

In the picture above, you see the house on Lake Drive in which I grew up — at least more than any other house — about six years solid, from 1967 to 1973. Apart from that, before age sixteen I had lived in four other houses in Valdosta, five in Moultrie, and two in Columbus. My father got transferred a lot, and my parents kept making profitable real estate deals that happened to involve moving. In any case, the Lake Drive house is still the showpiece of the street; because of a curve, you see it from a long way off, and the new owners, whoever they may be, have kept it looking very good. (The brick was originally red.) The first paid work I ever did was to carry away wood scraps during the construction of that house; but that's another story.

Pi day

Mathematics buffs, take note that tomorrow at the appropriate moment, the date and time, written American style, will be 3/14/15 9:26:53.58979...


Confessions of Valwood's first computer geek

In September, 1970, on a bright sunny day on which the heat of summer had at last begun to abate, so that Valdosta was merely hot and not sweltering, I arrived at Valwood’s old red brick building as a new ninth-grader. I was the kind of person who would nowadays be described as a nerd or a computer geek – but in those days we didn’t have those terms, nor the computers, nor the notion that such people are valuable because they can make the computers work. So there I was, bookwormish, socially isolated, scientifically inclined, and hoping only for a school that wouldn’t actively interfere with my education.

Click here to


Jupiter again

This is an even better rendering of the picture of Jupiter that I posted yesterday. What I'm using is the linked-wavelet enhancement described (sketchily) here.

RegiStax is marvelous software, but I wish it came with a clear mathematical exposition of what it's doing to the images. (This is science, after all.) PixInsight is better documented and also has wavelet enhancement; so far I haven't gotten results that are quite as good, but that may be because I am not as skilled at using it.



First decent picture of Jupiter this season. Part of the trick was setting the telescope up on grass (for steadier air) instead of concrete. Celestron 8-inch EdgeHD, 3× Meade Barlow and DFK camera at the Cassegrain focus (effectively f/30). Best 75% of 2700 video frames. AutoStakkert, RegiStax 6, Photoshop.

I did something slightly different with RegiStax that might also have improved the quality; more about that presently, when I've read up on it and am sure I understand it.

Remembering Don Parker

I failed to note the death on February 22 of planetary imaging pioneer Don Parker, whom I had the pleasure of knowing at least slightly. I last saw him at the ALPO in Atlanta in 2013.

Don was one of the few people who were successful at planetary photography during the film era. He then led the march into the digital era. His 1988 book (co-authored with Dobbins and Capen) remains a classic (and is still available)


What that "supermoon" was all about

Remember the "supermoon" back in September? Well, last night (March 6) we had the opposite — a "mini-moon" — a full moon with the moon near its maximum distance from earth.

This is a rough draft for a much more elegant picture I'm planning to make, from matched exposures of the moon with the same telescope and camera on the two dates. Celestron 5 (f/10), Canon 60Da, ISO 500, 1/500 second.

Last night's catch

Here are two more pictures from last night. Jupiter in unsteady air — not as blurred as my previous attempt a few nights ago, but not as sharp as I'd like — and a moonscape, specifically sunset over Mare Crisium.

Celestron 8 EdgeHD, Meade 3× Barlow, DFK camera, stack of the best 75% of about 3600 video frames, AutoStakkert, RegiStax 6, PixInsight.

Infrared black-and-white image with Celestron 5 telescope (f/10), DMK camera with IR-pass filter; again, a stack of the best 75% of about 3600 video frames, AutoStakkert, RegiStax 6, Photoshop.


Are happy days here again? Unemployment is down to 5.5%, which is almost as low as it can ever go for any length of time. (The absolute minimum is about 4.0%.) It was higher during most of the prosperity of the 1990s. And a very encouraging development is that according to Forbes, large employers are finding they must pay their rank-and-file employees more than minimum wage in order to get reliable workers to stay.


On the one hand, you can't compare today's 5.5% unemployment to the same number 20 years ago because workforce participation is different. Many people aren't looking for work — don't expect to be employed — who would have been in the workforce then. Many more are underemployed, unable to get the jobs in which they would be most productive.

On the other hand, the bubble isn't coming back. We will never be building houses and cars in such a frenzy again. Nor will we have the dot-com boom. (Did you notice that the smartphone app boom didn't get off the ground? For a couple of years everyone talked as if it were the whole future of computing. It wasn't.)

So lots of people are never going to get the kind of jobs they had, or expected to have, in the period 1995-2005. That was an abnormal economy.

The recession of 2008 may have scared some sense into us. Or not; I'm not sure. What I hope is that many Americans adopted a thriftier, more cautious lifestyle. That seems to be one of the reasons we aren't having inflation right now, in spite of "quantitative easing" — when people earn money, they use it to pay down debt, which contracts the money supply.

In the Roaring Twenties and again in the Roaring Nineties, lots of people did the wrong thing. During a period of prosperity, it would be rational to pay down debts and build up savings; then, when prosperity subsides, you draw down the savings and even run up debts if necessary to keep going. But in those Roaring years, prosperous people built up even more debts in the expectation of even greater prosperity that would make them easier to pay off in the future. (Thus McMansions, adjustable-rate mortgages, and "drawing out the equity" in your house as if it were cash.)

My own feeling is that caution is appropriate. We are going to progress more slowly in the future, largely because we don't have so far to rise. We now have a society where everyone who wants a reasonably good education can get it, and all industrial processes are close to being as well mechanized as they can be. There will be continued progress, of course, but we are no longer in a massive rise from serfdom to middle class; we are no longer overcoming removable obstacles that held us back.


How Dave Ramsey handled a women's issue

[Revised for clarity.] [And extended.]

As a Christian who is interested in economics, I try to keep an eye on the "Christian money management" subculture. And although I don't agree with him about everything, I was delighted with how radio talk show host Dave Ramsey handled a feminist issue the other day.

A middle-aged mother called to ask, "What advice would you have about how my daughters can find husbands who are good providers? I assume you believe it's the husband's duty to provide for the wife..."

He grabbed that question the right way. He explained that marriage is not just someone "providing for" someone else — it's two people teaming up to live their whole lives together. Each provides for the other, in different ways.

He added that there's nothing wrong with women working — his daughters are career women. (He could also have pointed out that pioneer farm wives worked just as hard as their husbands; there haven't been many pampered, idle housewives on the stage of history.)

He also pointed out that there's a lot to be said for women staying home with their young children. That's very worthwhile work, not idleness.

Then, as the coup de grâce, he said, "A problem I see fairly often is when a wife is a 'princess' and doesn't feel any responsibility for managing money — she just expects the husband to bring home money and spend it on her. Those are unhappy couples." (My paraphrase, not an exact quote.)

Well done, sir! It sounds like you may have prevented princess-hood from being passed down from one generation to the next.

Addendum: The question did, of course, have a more reasonable intepretation. Maybe the mother just wanted to help her daughters find husbands who would be reasonably financially successful.

The answer I would give — which I think would also be Dave's answer — is that the daughters need to learn how to manage money themselves, so that they can tell whether someone else is paying attention to the right things and making realistic plans. That's much better than choosing a husband by the elegance of his car or his ability to dance.

Short notes

Why do some web pages bob up and down when they're loading? Because of a basic error in HTML coding. The first part of a web page that gets to you is the HTML file, which contains the text and says what other files to load, mainly pictures. The HTML file is supposed to give the size of each picture so that the text can be laid out properly. If the size is omitted or is wrong, the text will move when the actual picture arrives. Apparently, some obnoxious advertisers have decided they like it that way.

Atlanta's motto should be "What used to be here?" During yesterday's trip I was struck by the number of buildings I had been in, forty, twenty, or ten years ago, that have been completely replaced. (I stayed in the Atlanta Cabana in 1973; does anybody remember that?) I suppose London was doing the same thing in the 1890s, which is why it's so full of Victorian buildings now. In Atlanta, even the roads move around. At least Manhattan has the same streets it had had for a long time; you can't find the Hippodrome but you can say what is on its site. Atlanta doesn't work that way.

Racism in mid-America: The Department of Justice report about Ferguson, Missouri, is alarming. And just a few years ago Omaha was trying to segregate its schools. I fear that some parts of the country may think racism is OK because they aren't the South. Let's keep our eyes on mid-America.

And I'm puzzled about Secretary of State Clinton's use of a private e-mail server for official business. The initial focus was on the fact that those e-mails wouldn't go into the official archives, but a bigger problem is that the unofficial server was at risk for being hacked. Who knows who read her e-mails?

This, by the way, is why employers have to allow a certain amount of personal correspondence on official e-mail accounts. I wrestled with this as a UGA administrator. If you have two e-mail accounts (personal and business), a fair bit of mail will go to the wrong one, simply because the people who are writing to you don't care, or don't have the right address, or don't know the difference. It's better to have some personal correspondence take place on the official account than the other way around. If you try to exclude it strictly, you'll drive away some of the official correspondence too.




Today's trip to Atlanta included an Emory office tower with some remarkable views. Here you see the sunlight breaking through the clouds north of midtown. And below you see the original Crawford W. Long Hospital, birthplace of the famous Melody Mauldin Covington.


Two generations apart

TOP: Your humble author, many years ago.
BOTTOM: Your humble author's grandson, Benjamin James Barrett.

Photo by Catherine Anne Barrett.


What color is that dress?
What it is, is overexposed


The Internet is abuzz with the question, "What color is this dress?"

The picture was posted on Tumblr with a question about the color. White and gold or blue and black?

I first interpreted it as white, or maybe pale blue, and gold, under bluish illumination. It looks like it was taken outdoors and the dress is in the (bluish) shade while the background is sunlit.

Others insist that it is black (or very dark) and medium-to-dark blue. And — surprise — they are right! Here, from Fox News, is a picture of the dress taken under good lighting, showing accurate color:

What happened? Obviously, the controversial picture was grossly overexposed, under warm-colored lighting. Hardly anybody is pointing this out, but it's easy to verify. Looking at the histogram below, we see that the picture has no true blacks (at the left) and has blown-out highlights (at the right). Those are symptoms of overexposure.

The picture was taken through a store window. You can see from the histogram that there is a golden-brown cast in the blacks; that is, blue goes farther to the left than red and green do. I think that came from warm-colored light reflecting off the window. You can see some of it in the second, uncontroversial picture. There may have been a lot more of it in the first. Indeed, true blacks in the original picture (in the object to the left of the dress) are brown. There is no black in it, which shows that black has been rendered as brown.

So... case closed... it is the work of a misadjusted camera and bad lighting. Or even a hoax or prank, a manipuated picture. My daughter Catherine Anne Barrett notes that the original picture may have been taken with a "vintage" filter to fade the blacks to brown, as in an old photograph. Information about the camera is missing from the JPEG file.

But is that the whole story?

No. The bigger mystery is why some people can see the original picture as black-and-blue, and others can't.

Apparently, you are more likely to see the dress in its true colors — that is, compensate successfully for the overexposure — if your room is dimly lit with warm-colored lighting. In that setting, your eyes and brain are predisposed to compensate for the brownish cast in the picture. What's going on is that the brain adjusts color balance whenever we see anything. We rely on our memories of what objects ought to look like and our knowledge of the color of the ambient light. This picture is good at tricking people into thinking the ambient light is something very different from what it really was.

Our memories are a particularly misleading guide in that case. There's nothing in the picture to tell us about the color balance of the picture. There are no skin tones or anything else familiar that would tell us whether the picture is light or dark, bluish or brownish. But how common are black-and-blue dresses, compared to gold-and-white or gold-and-pale-blue ones? I approached the original image feeling that black and blue was an unlikely color combination and that light colors were more probable.

An illusion of color vision may also be involved — a very common illusion, one we rely on all the time: If you mix red light and green light, you get the appearance of yellow light. (Similarly, blue and green make cyan; red and blue make purple.) If you use a magnifying glass to look at a yellow patch on your computer screen, you'll see there is no yellow in it, only red and green. Red and green do not make yellow light, they just look like yellow light to human eyes.

And the catch is, some eyes are more sensitive to red than others. That means a pale yellowish or brownish color, simulated with red and green on the computer screen, will look different to different eyes. Even without being color blind, you can have considerably different red sensitivity than the next person (differing both in total sensitivity and in peak wavelength). If you're less sensitive to red, the dark parts of the dress will look more neutral-colored, making it easier to interpret them as black. If you're more sensitive to red (as I apparently am), they remain golden. One way to make your eyes less sensitive to red is to have an environment of dim light that is warm and orangish (with lots of red in it), so your automatic color balance routine will turn down the red sensitivity.

And that's all I have to say about this week's discussion topic, except to point out one more thing: Once you start looking for them, you'll find lots of things that don't look right in color photographs. Comparing a color picture with the original subject is a surprising exercise! It's one of the reasons biological illustration (of living animals and plants) continued to rely on artists long after good color photography became available. Plenty of natural objects, especially flowers, reflect odd combinations of wavelengths of light and don't photograph correctly. Some textile dyes have the same property.

The new me

At the top of this page you will see a new portrait of me — one of a set of excellent pictures taken the other day by Krystina Francis.

She used a Sony A7S, and I got a quick look at it. I think it's quite promising. Built like a brick, easy to use, and (as we know from other sources) good for astrophotography. I hope to get to try one out for that soon.

If what you are looking for is not here, please look at previous months.