Jeff Duntemann's Contrapositive Diary Rotating Header Image


Odd Lots

  • I’ve mentioned this before in several places, but I will mention it again here and probably more than once again before it happens: On December 21, Jupiter and Saturn will be only one tenth of a degree apart. That’s one fifth the diameter of the full Moon. I’ve never seen two planets that close, and I’ve been looking at the sky now for 63 years.
  • As I mentioned in a recent entry, I’m putting my big 10″ Newtonian scope back together for the first time in close to 20 years. Most of the work lay in building a new base. (Termites ate the original, which I cobbled together out of scrap wood when I was 16.) The base is finished. The rest should be easy. With some luck I’ll get it all together and do a star test tonight. If my stars are in alignment, it’ll work. But hey, all stars are my stars, so I can’t lose!
  • While listening to Peter Hollens songs on YouTube, I stumbled across a remarkable women’s vocal ensemble: Brigham Young University’s Noteworthy. They’ve posted a number of videos, and all of them are amazing in terms of pure vocal harmony. Nothing I’ve seen tops their cover of “When You Believe” from the animated film Prince of Egypt. It’s the best song out of a very good bunch, and those ladies nailed it for all time.
  • I suspect that by now you’ve probably heard, but SF legend and former Analog editor Ben Bova died on November 30, of COVID-19 complications. He was 88. Ben taught for a week when I attended Clarion East 1973, and he was spectacular.
  • And as though that weren’t bad enough, Chuck Yaeger died this past Monday, December 7. Yaeger, to me, almost defines the word “badass.” He shot down 13 German warcraft during WW2, five of them on one mission. He rode the Bell X-1 to the sound barrier and beyond, and piloted the X-15 to the edge of space. He fought Death to a draw that lasted 97 years. Godspeed, General Yaeger.
  • Watch for Northern Lights from Thursday sunset to Friday dawn. (H/T to Hans Schantz.)

Bringing the 10″ Scope Back to Life

Joe Lill and 10 Inch Newt - 3-8-1970 - Cropped.jpg

When I was 14, I took an opportunity and started out on a very large project: A friend of mine bought an Edmund Scientific mirror-making kit, decided he didn’t have the time to pursue it, and sold it to me. The kit included a 10″ Pyrex mirror blank, a plate glass tool blank, and all the abrasives needed to grind and polish it. I did most of the grinding in my basement, using a defunct round wringer washer as a grinding station. I followed the instructions in the kit, along with whatever I could find in the library, and though it took a couple of months, in time I had a Pyrex blank with a smooth curve, focusing at about 67 inches. My goal was 70, so I came pretty close, and in truth, 67″ would make for a shorter and somewhat lighter tube.

Now, grinding is only half the job. Polishing the ground mirror surface took sophisticated methods to gauge the accuracy of the curve, which has to be a parabola to focus items at infinity (like stars) to a sharp image. I decided I was over my head, and did the sensible thing: I enrolled in a class at the Adler Planetarium on Chicago’s lakefront, which took up most of the summer that I turned 15. They had an optical shop in the basement that included the required Focault tester, plus a superb teacher, Ken Wolf, who helped me get the polishing done and mirror curve accurate. They were also able to aluminize it, and by that fall, I had a 10″ F6.7 parabolic telescope mirror accurate to 1/25 wave, which was bogglingly accurate for a first shot by a 15-year-old.

The rest of the scope took another two years and change to complete. A friend’s father made me a tube out of sheet aluminum. I built a tube saddle out of scrap wood and hardware-store aluminum stock. I had no tools more sophisticated than my dad’s circular saw and saber saw. And that was for woodworking–for metal I did it all with a hacksaw and files. I had some help from my high school machine shop teacher, who dug up a piece of iron that he said was hull metal from a scrapped battleship. He cut it to size on the big bandsaw for me. I spent many study hall hours in his shop on one of the lathes, boring out 2″ pipe fittings and making numerous small parts. I owe Mr. Brinkmann a huge debt of gratitude. Without his help and the use of his machines, I could not have finished the scope.

It was going to be a big scope, and a much heavier one than the 8″ Newtonian I had built from a Sam Brown book the summer I turned 14. I turned my attention to building a base. There was a lot of scrap lumber in the crawlspace. I had the notion of building a cement form out of scrap lumber and pouring a solid triangular concrete shape 36″ on a side with bolts embedded in the top for the battleship-metal mount.

So I built me a cement form.

Whoops. Doing some math and library research showed me that the concrete base would weigh at least 400 pounds. Yes, I could make it–but once I made it, I had no idea how I would move it. So I was left with a scrap lumber cement form…


FirstDateSketchTelescope - 325 Wide.jpgThe form was made entirely from 2″ dimensional lumber, from 2X4s to a scrap of 2X12. I could carry it around with only a little puffing. So I would use the cement form as the telescope base.

A lot more work and allowance money would go into the telescope before I finished it–more or less–in the fall of 1969. On an early date with a pretty 16-year-old girl I had met in church, I told her about the project and drew a picture of it on her little spiral notebook. (See left. She enjoyed talking about science. So did I. She married me in October 1976, and our flag still flies.)

I used that scope a lot, even though it was bulky and heavy and awkward to cart around. In 2000, I (finally!) poured a concrete base for it at our house at the north end of Scottsdale. (See below.) I bought a large plastic trash can to put over the scope to keep the weather off it, and enjoyed it tremendously. Well, we moved to Colorado in 2003. When I went behind the garage to fetch out the now-retired wood base, I discovered that the local termites had been feasting for a couple of years, and there was nothing much left.

I haven’t had the 10″ assembled since. And it’s now about damned time to get to work.

10 inch with Michael Abrash - 2001 - 500 Wide.jpg

I’ve spent a couple of weekends messing with it. Yesterday I bolted the aluminum tang to the base, and although there will be some refinements, what you see below is pretty much what you’ll see when it’s in service.

New 10 inch wood base 1- 500 Wide.jpg

The equatorial head is still workable, though tremendously heavy. I hope to build a new one out of aluminum. In the meantime, I see no reason why I can’t have it up and working by the time of the Great Conjunction of Jupiter and Saturn on December 21. The two giant planets will appear just 6.1 arc-minutes apart, close enough to see in the same eyepiece field, and closer in the sky than they’ve been since 1623. A conjunction of this sort is said by some to be the Christmas Star that the Three Wise men followed to Bethlehem. Miss that? No way!

More on the 10″ scope project as it happens.

Odd Lots

Odd Lots

Ready for the Eclipse

Solar Projection Setup 500 Wide.jpg

I put the 8″ scope together on the driveway to make sure nothing was amiss (and to be sure I could find all the parts) before packing the whole thing off to the parking lot of St. Raphael’s Episcopal Church. Observing the eclipse where I live is impossible, because I’m on the eastern slopes of Cheyenne Mountain, which rises almost 30 degrees above the western horizon. Today’s eclipse will occur while the Sun is setting here in Colorado Springs. In fact, even with a perfect western horizon, the Sun will set before the eclipse is fully past.

The church is almost seven miles east of us, and while there will still be mountains on the horizon, they will obstruct nowhere near as much of the sky as they do from my driveway. It also becomes an opportunity to have parishioners who may be interested come out and see what of the eclipse can be seen from here. The full annular eclipse will be visible from Albuquerque, about 250 miles south of us. We’d considered heading down for it, but there’s just too going on in our lives right now to spare the time.

The projection screen is simple Hobby Lobby foamcore attached to a length of aluminum angle stock with a 1/4-20 threaded hole at its center. I had to crank up my tripod almost to its vertical limit to get it to catch the image of the noonday Sun. The eclipse here doesn’t begin until 6:27 PM, when the Sun will be a great deal lower in the sky. Maximum coverage is about 7:30. The Sun sets here at 8:09.

Of course, all of this assumes that it will be clear later this afternoon. There are a lot of big puffy cumulus clouds up there now, and we had a thuderstorm here yesterday evening. So far so good. I’ll let you know how it goes tomorrow.

Odd Lots

Odd Lots

  • Printed book sales fall, and ebook sales rise by 115%. Something’s Going On Here.
  • I bought an iPod Touch from Jim Strickland and am currently figgering it out. Although I was surprised that it won’t display .mov videos, this article makes much clear about Apple’s video formats.
  • Michael Covington’s 2008 tutorial on reading email headers to spot phish and phakes is worth reading again.
  • Richard McConachy sent me a link to The Great Wetherell Refractor, a hand-made 200mm F9 with some of the guldurndest metalwork in it.
  • There was a horned gopher during the Pleistocene. Really. It is the only horned rodent known, and the smallest horned mammal.
  • From Henry Law comes a reminder of an xkcd item from a while back. For heavenly performance, ground your receiver in a jar of holy water!
  • And that led to this one, which (Ben Franklin groupie that I am) has always been one of my favorites.
  • I haven’t had a monster zin in some time, but last night I opened the bottle of Klinker Brick 2007 Old Vine Zinfandel that’s been sitting on the rack for almost two years. About $18 if I recall. At 15.8% alcohol, it’s among the strongest reds you’re likely to find that aren’t port. Dry but not bitter, with strong spice and enough fruit to balance the buzz. I had about 100ml. Puh-lenty!
  • A cool hack and great visual humor. I have a couple of these little KingMax USB sticks (courtesy Eric Bowersox) and although it would be a bad use of my time, I’m sorely tempted.
  • Accidental visual feast: Search for “steampunk jewelry” on Google Images. My favorite would be this one, which I would title “Time Flies.”
  • In addition to bathroom heaters like the one I bought the other day, the Fitzgerald Manufacturing Company was well-known for making vibrators, (PDF) albeit not the kind that generated plate voltage for car radios! (Could this have been the original killer app for mains electricity?) Thanks to Jim Strickland for the link.

Odd Lots

  • Our good president is creating czars right and left, to the point where you can’t tell the czars without a program. So maybe we need a czar czar–I know a guy named Binks who could do the job…
  • Jim Strickland sent me a decent video demonstration of superfluidity in liquid helium. Liquid helium had a starring role in my 1980 story “Cold Hands,” and Richard Bartrop’s cover image of my upcoming story collection Cold Hands and Other Stories includes Richard’s visualization of liquid helium floating free in atmosphere at zero-G. I don’t think we’ve ever fussed with liquid helium in orbit, but if we have, I’d like pointers to any mentions.
  • In my novel The Cunning Blood, I postulated fluidic computers, which use fluid pressure and flow rates as the encoding units of information. People think I made this up completely, but not so: The technology was in use as early as 1948, and was written up in Popular Mechanics in the 1970s. (That’s where I first heard of it, though I can’t find the citation right now.)
  • If you’re at all interested in the future of the publishing industry and newspapers in particular, be sure to read James Fallows’ take on it. Ad-supported print media are being bled white by eBay and especially Craigslist, which is the direct digital analog of print classified ads.
  • From the Words-That-Sound-Exactly-Like-What-They-Are Department: “Dudelsack” is German for “bagpipe.”
  • Ethanol is a terribly inefficient use of corn (corn stoves that burn it for home heat are a far better use of corn as fuel) and it may destroy engines as well. Thanks to Pete Albrecht for the link.
  • Some years ago, while bumming around my old neighborhood in Chicago, I noticed an observatory dome on an addition to a late 40s house about three blocks from where I grew up. It was right across the street from Olympia Park, where I tried and failed several times to become good at softball. Pete Albrecht noticed that the New York Times did an article on home observatories a couple of years ago, which included some photos of the observatory, built by an accountant named John Spack.

Odd Lots

  • While chasing an interesting “out of the blue” idea that came to me while exercising the other day, I happened upon an RV surplus shop. Not surprisingly, it's in Elkhart, Indiana (Ground Zero for the American RV industry) and it sells leftovers and overstocks of RV parts and interior furniture. If I were to want to built a custom RV dinette table with a built-in keyboard, well, this might be the place to start.
  • Good grief: Has Big Media run out of Republicans to torment? ABC News posted this story about the pastor of Obama's Chicago church, who repeatedly condemns the US in his sermons and tells his people that they should be singing “God Damn America” instead of “God Bless America.” Expect those sermons (which are offered for sale by the church) to become very popular in coming months.
  • Illinois is famous for a lot of things, but being the historical capital of manufacturing of fraternal organization initiation and hazing equipment is not one of them. However, the De Moulin Company of Greenville, Illinois, now known for making band uniforms, used to do a big and almost unimaginably bizarre business manufacturing expensive gag items used to make new Masons and Elks feel like one of the gang. The precise psychology here is obscure to me (the last remotely fraternal organization I joined was the Boy Scouts) but the devices are just insane. Browse and boggle.
  • Here's another source for home-made telescope optics and truss telescope kits up to 32″ in clear aperature. Even though I'm not a big Dobsonian fan, the scopes look good, and if you want light-gathering power above all else something like this is as good as you're going to do short of a full-concrete observatory. The optics are not cheap, but they're good. (Thanks to Pete Albrecht for the link.)
  • Also from Pete comes a link to a site selling Swiss Army Ohmmeters. Should the Swiss Army encounter resistance, well, they'll be ready.
  • Mike Burton (who worked in the industry for some time) wrote to say that “double shot” keyboards are no longer produced due to their expense. A double-shot keyboard is one in which the keycaps are molded in two steps: One step to mold the body of the cap, with a void in the shape of the letter, and a second to fill the void with black plastic. Such keycaps never lose their legends, like my decal-equipped Avant Stellar is now doing at great speed. I guess I had better stock up on period Northgates.
  • We have evidently found the gene that triggers the onset of puberty. One wonders what suppressing this gene would do long-term. What would be the psychology of a 75-year-old boy who had never gone through puberty? Larry Niven toyed with the idea in World Out of Time, speculating that stopping puberty would stop aging, but I intuit that much more could be done with it. Would I give up sex for a shot at becoming immortal? (Answer from this side of the fence: No. Ask me in 1962 and you might have gotten a different answer.) Much depends on whether emotional maturity is a process inherent in or only affected by puberty. Sooner or later some renegade will try this, and we'll know.

Junkbox Telescope Gallery

Some years back I posted Jeff Duntemann's Homebrew Radio Gallery, and for reasons unclear it's become one of the most popular pages on my site. (Tube construction may not be quite dead…) So a while back I wrote up and (almost) finished a page about all the various telescopes I've built out of junk since 1966. Longtime Contra readers have seen some of the photos, but a few are new scans of prints I've had in a box for decades.

Jeff Duntemann's Junkbox Telescope Gallery sat unfinished on a thumb drive for some months, until I finally bore down and finished it a few days ago. It's not a how-to; there has never been and will probably never be a better junkbox telescope how-to than Sam Brown's classic All About Telescopes, which is in turn a compendium of shorter booklets that Brown published through Edmund Scientific in the early-mid 1960s. $14.95 is cheap for a book like this. If you ever have the least inclination to put together a scope from scratch, buy Brown's book first.

The page is mostly a photo collection, with some odd notes on how I did what I did. Note well that you don't have to grind and polish your own mirror as I did. Ready-made 8″ primary mirrors can be had for $300 or sometimes less, and the rest of the scope can be, well, junk. Also note that I think Dobsonian mounts are silly: With a 2″ 45° street elbow you can have something approaching an equatorial mount if you live in the US.

Building scopes like this is mostly a lost art, and there are definitely advantages to scraping up the cash for a Meade or a Celestron. (Tapping in “M31” on a keypad is less messy than lying on your back in a cowfield and sighting the nearly invisible object along the edge of the tube.) But it's a good kid project, because when you're done you—and any involved kids— will know exactly how it works, and that's worth something all by itself.