Michael A. Covington    Michael A. Covington, Ph.D.
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Popular topics on this page:
Sharp full-face Moon or Sun with f/10 SCT
Bad graphic design at the AJC
UFO over St. Mary's Hospital
Trying to pair me with the wrong woman
RichTextBox.ScrollToCaret crashes with AccessViolationException
Warning signs of fake e-mail
A rant about grep
So you want a telescope for Christmas?
Moon (1 day past full)
Moon (first quarter)
Moon (rills — Rima Hyginus and Triesnecker)
Moon (Apennines)
M35, NGC 2158, NGC 2175
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"Thy rocks and rills"

Despite unsteady air, I did some fairly good lunar imaging on the evening of November 29. Here's the full face of the first quarter moon, a stack of five still images taken with the Celestron 5 (and f/6.3 compressor, which I do not think helped the image quality):

Color saturation has been increased so that you can see the difference between different types of lunar rocks.

And here are some rills (long, meandering, narrow valleys), namely Rima Hyginus (bisected by a crater) and the rills around the larger crater Triesnecker:

Finally, here are the lunar Apennine Mountains:

The latter two pictures were taken in infrared light with a DMK video camera and my 8-inch EdgeHD telescope. Each is a stack of a large number of video frames, digitally combined and sharpened. They are not very good, relative to what this telescope can do, because of the unsteady air.


So you want a telescope for Christmas?

If you're thinking of buying a telescope, either for yourself or for someone else, here's some important advice. It's easy to spend a lot of money without getting what you actually would enjoy having. There's some learning to do first.

When anyone asks me to help them choose a first telescope, I ask two questions.

(1) How well do you know the sky? Are you already looking at the sky avidly with the unaided eye and binoculars, finding things on maps, identifying objects? Do you know the phases of the moon? Can you point to Orion or Jupiter in the sky? In short, if you had a telescope, do you know what you'd aim it at?

If not, then you're probably not quite ready for a telescope. Some good books, a pair of binoculars, and some time out under the sky need to come first. The books and binoculars will remain useful as you become a more experienced astronomer.

(2) Have you looked through other people's telescopes? How well do you know what the view through a telescope looks like? I ask because looking through a telescope is nothing like looking at a long-exposure photograph. If the views that we see in space-probe pictures could be had in a telescope, we wouldn't need the space probes.

But the telescope shows you some things a picture can't capture, such as the enormous brightness range in the Orion Nebula, and I never get tired of seeing things "live." To get much use out of a telescope, some training of the eye is required. You don't see everything immediately.

If you're past the beginner-with-binoculars stage, you may know exactly what kind of telescope you want. If not, I suggest starting with a small portable refractor such as the Celestron Travel Scope (see the picture). A telescope like this is easy to use, gives good views of a variety of objects, and, because of its portability, will remain useful after you get a bigger telescope later. Several companies make comparable instruments.

Buy your telescope from a telescope dealer, not a department store that knows nothing about telescopes — unless you want to take a risk. There may be nobody in the whole store who can tell you if all the parts are present and are working correctly! Magazines such as Astronomy and Sky and Telescope have ads for plenty of reliable dealers. Among mail-order dealers, I particularly recommend Orion, Oceanside, Astronomics, and (locally in Atlanta) Camera Bug.

Remember that a bigger, more advanced telescope is always harder to use and you can easily find yourself longing for a smaller, simpler, more portable one!

Go for sharpness, not power. Unlike microscopes, telescopes don't work at 600× — not even the biggest one you can afford. The laws of optics and the unsteadiness of the earth's atmosphere limit what you can see at high power; you can't magnify detail that isn't there. Instead, go for a sharp, low-power image. I usually use my 8-inch-diameter telescope at 100×. A smaller telescope will work well at 20× to 50×.

Remember that a computerized telescope mount won't learn the sky for you. I'm the one who wrote the book on computerized telescopes, and my experience is that the computer is a great help for an experienced observer who is constantly aware whether it is working as intended, but it can be frustrating if you don't know the sky very well and try to "fly blind." Anyhow, with a limited budget, you should spend your money on optical quality.

For more advice, contact your local astronomy club (if there is one) and look at the beginners' page at Orion Telescopes.



I think my technique is getting better. This is a carefully focused stack of 5 still images taken through the Celestron 5 and Thousand Oaks full-aperture filter. The system included an f/6.3 compressor, which I do not think helped the image quality.

As you can see, we now have a scatter of small and medium-sized sunspots. You can also see a bit of granulation and faculae (light areas). The impression of a light rim around each sunspot, however, is probably an image processing artifact.


Thanksgiving prayer

"Creator God and Ground of All Being, we thank you for letting us live in this time, in this place, in these circumstances, among these good people, and within this beautiful and extravagant creation!"

— Jeff Duntemann


M35, NGC 2158, NGC 2175

One last picture from the evening of November 18. The big star cluster is M35 in the constellation Gemini; the much more distant fuzzy one just to its lower right is NGC 2158; and at the very bottom of the picture, at the middle of the lower edge, is a nebula I didn't even known I was photographing, NGC 2175.

Stack of five 30-second exposures, Sigma 105/2.8 lens at f/5.0, Canon 60Da on iOptron SkyTracker.


Caution about "Black Friday"

Advertisers are bombarding us with "Black Friday specials" to draw attention from a fact that several people have confirmed — the bargains on Black Friday may not be as good as what you get on other days.

The idea is to whip you up into a frenzy so you don't actually compare prices.

Of course, there are always some "first 5 customers only" specials with very low prices. Those are the bait, to draw you in. You won't actually get them.

Anyhow, do I need to buy a lot of stuff in the first place? Actually, no. There are relatively few items that I'm prepared to buy in the near future, and they don't have anything to do with Black Friday. I'm not going to get caught up in a spending festival just because retailers want me to be.

Anyhow, the real bargains are between Christmas and New Year's, when everybody is trying to avoid inventory taxes.




I've probably photographed southern Orion more than any other part of the sky. The three stars of the Belt of Orion were the first part of any constellation that I learned to recognize, back in the March of 1968, and I've remained fascinated by the objects in this field, especially the nebulae.

Here's one more. You can see the Great Nebula (M42) below center, some reflection nebulosity (bluish) above it, emission nebulosity (reddish) to the left of the Belt, and the small but bright reflection nebula M78 at the upper left corner.

I can't claim that this is a particularly great photograph, but at present, using relatively new equipment, I'm taking a lot of pictures just to be more familiar with what the equipment can do. Canon 60Da on iOptron SkyTracker, Sigma 100/2.8 lens at f/5.0, stack of five 30-second exposures, processed with DeepSkyStacker and PixInsight.

Compare to this one. One day I'll photograph this star field from a dark country site and pick up much more of the faint red nebulosity.


A rant about grep

As everybody knows, grep is the UNIX command, also available in many other operating systems, for finding lines in files. For example,

grep blah <myfile.txt >newfile.txt

will copy from myfile.txt to newfile.txt all the lines that contain "blah". The name stands for global regular expression print.

As everybody also knows, grep uses regular expressions.

Regular expressions are a notation for matching characters with alternatives and repetitions. For example,

grep [0-3] <myfile.txt >newfile.txt

finds all the lines that contain a digit between 0 and 3 inclusive.

Regular expressions ("regexes" to their friends) are powerful. The regular-expression matcher can count, can backtrack, and can extract substrings. The programming Perl is built around a regular expression matcher. Regular expression matchers are also built into C# and Java.

The trouble is, there's more than one grep. The original version, called grep, implements a now-obsolete syntax for regular expressions. The regular expression syntax best known in the modern world is implemented in egrep (extended grep). If you use grep only occasionally, you may not be aware of all the differences.

And one of them bit me this evening.

In egrep and all sane parts of the world, | is a special character when used in a regular expression. It means "or". To prevent this or any other special character from being used specially — that is, to denote the character | itself — you put a backslash in front of it: \|.

I wasted a good half hour fighting with the fact that in plain grep, it's the other way around. I dimly remembered that | wasn't a special character in plain grep. What I didn't realize was that, in plain grep, \| means "or", and as an expression by itself, \| means "nothing or nothing" and is deemed to match anything.

That is, the meanings of | and \| in plain grep and egrep are exactly reversed.

My new year's resolution is not to use grep any more. From now on it will be egrep. Unless I don't need regular expressions, in which case I'll use fgrep, which is faster and doesn't treat any characters specially — what you see is what you get.

By the way, I do not share the fascination with regular expressions that many programmers do. Yes, they're powerful, but they don't have quite as much computational power as people think. "Regular expression" is a technical term in the Chomsky hierarchy of formal grammars. I can't give you a regular expression to parse the whole English language; Chomsky proved it.

My real problem with regular expressions, though, is that they are the most illegible programming language that has survived into the 21st Century. (Worse ones have existed but died out.) A language in which a computation can be expressed as


cannot claim to be the epitome of clearness. That barbarous-looking formula is a regular expression for any HTML tag plus its closing tag and the material in between. In this language, \1 is a string variable. Got it? No?

I would rather write two or three times as many characters and have something a human being can read.

A correspondent points out that it is now considered better practice to write grep -E and grep -F for egrep and fgrep respecctively.

So my new year's resolution becomes: With grep always write -E if there is a regular expression and -F if there isn't; never leave it to its own devices.

I would very much like to see someone invent a new, more readable, more consistent, less concise notation for regular expressions in which it is perfectly clear whether each character is a literal character or a metacharacter — maybe use extra quotation marks to make the distinction.



How to recognize fake e-mail

Here's a nice example of warning signs you should notice when you check your e-mail. This message is not from FedEx or anybody I've ever done business with, and I'm sure its purpose is to lure me to a site that do me harm, maybe trick me into giving them passwords or maybe infect my computer with a virus.

Look at the warning signs:

  • It's not from FedEx even though it claims to be. It's from an address I've never heard of.
  • It contains bad English. That's a sign of an overseas scammer. "Arrived at November 17"? Really?

    Fraudulent e-mails often have bad punctuation, too. They may fail to space after a period "like.this" or insert extra marks joining words ("every-housewife needs^this") as if we wouldn't notice. They may be using random punctuation to keep their messages from being exact copies of each other.
  • Finally and most importantly, when you mouse over the button, you see another address you've never heard of, seemingly unrelated to the first one.

The most important Web safety tip that I can give anyone is, "Stop and think. Things may not be what they seem."

The second most important is, "Before you click on a button, look at the address that pops up at the bottom of your screen." If it's supposed to be a link to a major corporation but doesn't use that corporation's net address, it's likely to be fake. If it ends in a code for the wrong country (like .ga for Gabon claiming to be a site for Kroger coupons), don't even think about clicking.

It's sort of like recognizing telephone area codes. Thirty years ago, if someone asked you to call a number with an area code you'd never heard of, you'd know it wasn't local, and you might hesitate to call it. E-mail and the Web are the same. If an address doesn't make sense, it might not be what people are claiming it is.

Note by the way that the FedEx trademark in the message proves nothing. Anybody can copy a trademark from any web site.

Two afterthoughts: (1) This spammer in fact did not get the FedEx trademark quite right, but my point was, they could easily have copied it perfectly, and that still wouldn't prove anything. (2) I think this spammer is looking for dumb victims. They want to scare away people who will recognize obvious warning signs. The ones who remain, and who click on their link, will be naive enough that they can be lured into real danger.

And a correspondent points out another warning sign: The sender doesn't quite seem to know who you are. If e-mail claims to be from a person or business who knows you, but does not use your name, it may well be fake. E-mail addresses aren't secret, but they're also not in the phone book. If someone doesn't seem to know who you are, sure enough, they probably don't!

The flip side of this is when the sender claims to know more about you than he really could. Your e-mail address isn't tied to your location or your telephone number. When you get e-mail about "your neighborhood" and it doesn't name the neighborhood, you're dealing with a faker, just like the people who call you on the phone about "your credit card" and want you to tell them which credit card it is!

Please feel free to share links to this message.

See also Why older adults are especially vulnerable on the Internet.


The Hyades

The Hyades, a stack of four 30-second exposures with the same equipment as yesterday (scroll down). This star cluster is the face of the bull (Taurus). The bright red star Aldebaran, the bull's eye, is not a cluster member.

Why do the stars have cross-shaped spikes? Because I put a pair of thin wires, crossed, in front of the lens to create diffraction. They are mounted on a lens shade and are present almost every time I use this lens. Additional, smaller, spikes are due to the polygonal shape of the iris diaphragm.


A stroll through Cassiopeia

On the evening of November 18, it was very clear but cold. I got the iOptron SkyTracker out and took some pictures of the sky from my home in Athens, Georgia. It was definitely not a dark country sky, but I could see the winter Milky Way, which is seldom the case here.

Here you see part of Cassiopeia, a stack of five 30-second exposures with my Canon 60Da and Sigma 105/2.8 lens at f/5.0 (yes, 5.0). Note the subtle lanes of dark nebulosity (dust clouds) that run through the region, as well as the star clusters and a nebula (NGC 281) near bottom center.

I submitted the picture to astrometry.net and let their computers identify objects. Here's what I got:

This is worth doing again from a darker site.


Mumble dot com

An exhortation to anybody who advertises on radio: A web address is useless if you don't reveal how to spell it.

Maybe your name is Mxyzptlk and you've always pronounced it Mac. If you say "Mac dot com," other people are not going to type mxyzptlk.com. That is true even if in your experience Mxyzptlk has always been pronounced Mac. Other people know other ways to spell Mac.

This is a common fault in radio commercials. Most recently, I encountered a carpet cleaner called either Zerores or Zerorez, I can't tell which. Both spellings are equally good renderings of the same pronunciation. Another recent example is "Blue-Ray" or maybe "Blu-Ray" or "Blueray." If you don't tell us which one you mean, we'll never know.

Then there are who mumble and don't pronounce their name clearly in the first place — "mumble dot com." They often pronounce "dot com" very clearly because it's new and unfamiliar to them. But they've know their own name for a long time, and they don't think they need to say it very clearly to recognize it. Remember, you're speaking to other people, not just to yourself!


A Windows programming ghost story
RichTextBox.ScrollToCaret crashes with AccessViolationException
Excel 2010 displays spreadsheets with tiny row height, no text

Late last night (November 12), one of my main software products (a custom application for a client) started crashing with an AccessViolationException triggered by any call to RichTextBox.ScrollToCaret. The symptoms were similar to those described here, but not involving anything outside of plain WinForms in C#.

This is very bad, for two reasons. AccessViolationException usually means that memory has been corrupted in an uncontrolled way — exactly what .NET Framework is designed to prevent, no matter how klutzy the programmer may be. And the code had been unaltered and running reliably for several years.

I found that ScrollToCaret only crashed when a font change had been made shortly beforehand. I was ready to simply remove the font change to stabilize the program, but it was late and I wanted to knock off for the night. So I opened Excel 2010 to log my hours.

And Excel was not in its right mind. My spreadsheet displayed with the text blank and most of the rows incredibly shallow (about 4 pixels high). I retrieved the previous version of the spreadsheet, and it was similarly afflicted.

To make a long story short, rebooting didn't fix it, but waiting overnight for one more Windows update did. Some Windows updates were apparently in the process of being installed when the original problems arose. This morning, by the time I got to the computer, my program was no longer crashing and Excel was working properly again.

The moral? Windows updates can work mischief. But that's no reason to avoid them. Instead, if things seem to go wrong, keep updating, and the next one will fix it. It's much worse to run a version of Windows with known problems because you're afraid of updates.

Something lunar

In an attempt to practice what I was preaching, I photographed the moon on November 7 with my trusty 1980-vintage Celestron 5. I think I've achieved good, though not excellent, overall sharpness. There was some dew on the front lens that I didn't notice until too late. Also, I accidentally left an f/6.3 compressor in the system, and I think it harmed the overall image quality.

This is a stack of three exposures with a Canon 60Da. They were converted to TIFF with Photoshop, then stacked and sharpened with RegiStax and further processed in Photoshop, including increasing the color saturation.


Trying to pair me with the wrong woman...

It was nice of The Danbury Mint (which is not a mint) to send me this custom-printed mailer. (You're looking at the outside of the envelope, there for the mail carrier and everybody to see.) However...

My wife's name is MELODY !

I do have a daughter named Sharon, so this isn't totally scandalous in my case.

But if they can make this error, think how many other men they have paired with the wrong name. Surely, by random chance and circumstance, some of them must have been names that aroused real jealousy or suspicion.

Will anyone sue The Danbury Mint for alienation of affection?

Don't go to the doctor on Veterans' Day...

...or any other federal holiday. Too many people go to the doctor (and pharmacy) that day. I had to circle for half an hour to get a parking space at Sharon's doctor today, then go to two Krogers to fill a prescription because the first one was out of stock.


UFO over St. Mary's Hospital

Here's a flying saucer that I photographed over St. Mary's Hospital the other day.

What is it really?

A reflection of a recessed overhead light fixture, the kind that is a 6-inch-or-so hole in the ceiling with a light bulb in it. The bulb in this case was a rather bulky compact fluorescent with a long U-shaped tube; a conventional bulb would have resulted in a smaller "hot spot" at the bottom of the UFO.

I was indoors, looking out, and the light fixture was above me.

It's surprising how this mimics the kind of "flying saucer" that was repeatedly seen and photographed in the early days of UFO enthusiasm.


Quick update

Melody continues to make a good recovery from "the third of two hip operations" as we call it, and she will move to a rehabilitation facility (to get physical therapy while still receiving IV antibiotics) very soon. I'll post more news shortly.

What bad graphic design looks like

The Atlanta Journal-Constitution once had the good sense to offer Melody a job as a graphic designer. At the time, she was art director of the Marietta Daily Journal, and she couldn't accept the offer because she was about to marry me and move to California.

Three decades have passed, and whoever is doing that job now has made a big mistake. As of today, this is what the AJC's web page looks like:

That's supposed to be a newspaper? How are you supposed to find anything on that? Instead of a column or two of easy-to-skim headlines, they have big squares, three quarters empty, with tiny print in them. Read it with a magnifying glass.

In technical terms, the ink-to-information ratio (or more precisely, in this case, space-to-information ratio) is terrible.

Note by the way that this is the top of the front page of a newspaper, and there's almost no news in any prominent position. The composition of Congress has just changed, and the political world is sizzling; the Dow Jones average has just hit a record high; but the AJC doesn't seem to have noticed either of these things. They do not seem to be on the front page at all! The most prominent story on the whole page, lower down, is about the sale of a TV star's mansion.

A dying newspaper? An empty-headed person running it? Who knows? Obviously, I'm going to have to get my news from somewhere else.


Short update

A corrective operation on Melody's hip was successful on Monday and she is making a good recovery. After a total of about a week in the hospital, she will very likely go to a convalescent care facility for a couple of weeks to recuperate, since she will still be receiving IV antibiotics and special wound care. I am reading a lot, and even doing some work for clients, but not blogging, partly because I create the blog using a server at home that has no remote access.


We have a complication...

Melody's recovery from the October 10 hip surgery is no longer uncomplicated. She has developed a sudden infection. On Friday evening, she went from as healthy as could be expected to very sick within just a few hours. The next day, she was admitted to St. Mary's Hospital, and tomorrow (Nov. 3) she will have an operation (probably the first of two) to clean out the infection.

Your prayers are appreciated.

Best practices for taking a full-face photograph of the Sun or Moon with an f/10 conventional Schmidt-Cassegrain telescope

While I sit with Melody, I am doing a lot of reading, web browsing, and occasional calculating. (I'll segué into working on clients' projects soon.) What I can't do is create blog entries there, since they rely on files that are on my home LAN. Anyhow, here are some of the fruits of the calculating.

Taking a sharp full-face picture of the Sun or Moon with an f/10 conventional Schmidt-Cassegrain is apparently feasible, despite field curvature, if the following practices are followed:

  • Center the Sun or Moon in the field of view.
  • Focus critically on a zone 70% of the way from the center to the limb of the Sun or Moon. (This is for all f/10 conventional Schmidt-Cassegrains regardless of focal length.)
  • Use vibration-free mode ("Silent Shooting" on a Canon).
  • Use a pixel size about 10 microns or larger. For the Canon 60Da, this implies superpixel mode (available in PixInsight) or downsampling ×2.
  • If multiple frames are taken for stacking, they need to be almost perfectly aligned already, so have the drive running and do not change the aim or focus.

When opportunity permits — which might be any night after visiting hours — I'm going to try this and see how well I can do. For my best so far, see October 30.

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