Jeff Duntemann's Junkbox Telescope Gallery

 

So You Want to Build a Telescope? Think: Junk!

I did. It was a common enough thing when I was a kid in the 60s, and I did it a lot when I was quite young. I had Scotch-taped together a sort of pirate spyglass out of paper towel tubes and a couple of old lenses I had gotten from Uncle Louie when I was only 10. It wasn't much of a telescope, but it hadn't taken any money or much time, either, and its view of the Moon was breathtaking.

My parents bought me all the necessary optics for an 8" Newtonian telescope for my 8th grade graduation in 1966, and I set about furiously building a tube and mount for it. This took me until the fall of 1966, but the telescope, when it was completed, astonished me at what it would reveal of the night sky.

That was over 40 years ago, and I mostly blundered my way along, guided by library books like Jean Texereau's How to Make a Telescope. Not long after, I discovered the several short books (almost pamphlets) by Sam Brown on telescope making, and I still consider them the best guide for building simple Newtonian scopes ever published. The pamphlets were later gathered into a single bound volume called All About Telescopes, which is still available from Edmund Scientifics ($14.95—cheap!) and is a must-have for anyone even contemplating a home-constructed telescope, and especially one made mostly from junk. Sam Brown liked junk—he was writing in the early-mid 1960s, when money was scarcer than it seems to be today—and he made excellent use of it. The book is mostly illustrations, and those mostly superb, all hand-drawn by the author.

This Web page is not a tutorial on building telescopes; Sam Brown can give you that. This page is a picture book of some of the telescopes I've made since 1966, to give you an idea of what's possible, as well as convince you that a geeky 8th grader working with nothing but hand tools, scrap lumber, and pipe fittings, can unlock a gateway to a side of the universe invisible to human eyes. Some of the photos are ancient and badly taken, but bear with me: I have newer and better photos of some of those same old items.

The telescopes here will not perform like a Meade or a Celestron, and building a computer-controlled drive is something I never managed. On the other hand, you won't have to spend $4000 and up to look at Jupiter or globular clusters like M13. Obession Telescopes are fine if you're obsessed, but if you're a Maker and are looking for an interesting new species of project, well, consider it. The optics can be purchased ready-made; grinding your own mirrors is mostly a lost art these days. The rest of it, as you'll see, is hand-tool territory. I make telescope parts with a lathe because I have a lathe, but I made telescopes parts in my dad's vise long before I had anything better than a hand drill.

Parts and optics for home-built telescopes are still available. Here are some places to look:

Meridian Telescopes Scope City Scopetronix Surplus Shed

Also, you see telescope parts and optics come up on eBay fairly regularly.


 

The Texereau Square-Tube 8" F8

This photo is from September 1966, just after I had started high school and just before I had completed my original square plywood tube 8" scope. (And yes, that's me at 14. Egad.) The tube was 1/4" plywood with 1X1 pine stringers in the inside corners and 1/2" plywood strengtheners on each end. There was a hinged hatch (not shown in this photo) for installing and removing the main mirror. The tube design was verbatim from Texereau; I did not have the Sam Brown material at that point. Below is a better photo of the scope at my family's summer place near Third Lake, Illinois, about a year later:


The diagonal mirror was supported by a spider mount made entirely with hand tools. The rod on the side supported a camera mount using chem lab ring stand fittings. (The camera mount itself is not shown here, and I don't have a photo anymore.)

Below is a drawing of how a Newtonian telescope works. (Drawing from WikiCommons.) A parabolic mirror (left) reflects incoming starlight to a focus. However, the light cone is reflected 90 by the diagonal mirror so that the focus point occurs at or shortly before the eyepiece. A rack-and-pinion mechanism allows the eyepiece to be moved along the light cone's axis, so that the lenses pick up the light at just the right point to focus the image at your eye.

People often wonder if the diagonal mirror casts a round shadow at the center of the image, but it doesn't. The diagonal mirror cuts down a little bit on the amount of light that reaches the mirror, but because it only blocks parallel rays, its shadow is dispersed throughout the light cone and is not seen as a blockage.


 

The Spiral-Tube 8" F8

I used the plywood tube as shown above for two years. The tube was heavy and ungainly, and I swapped in a length of 10" spiral aluminum vent pipe (the type you see up in the ceiling of techno coffeeshops) in 1968, making for a much, much lighter telescope:

The pipe mount is the same, and I simply built a new tube saddle that would accept a round tube. (I did learn in trying to paint the pipe mount black that galvanized iron pipes do not take paint very well. Paint will flake off in a matter of days. Leave 'em as they come.)

Note that this telescope still exists. Not only that, it's the scope I probably use more than my larger, more elaborate 10" scope that I'll discuss a little later. The reason? It's light, and simple, and easy to schlep around. Below is a photo from 2003, and shows the scope essentially as I use it today:

All of the pipe fittings except for the counterweights axis are standard, Home Depot 2" pipe size. (2" pipes are actually larger than 2" in outside diameter; the 2" is roughly the inside diameter.) The main pipe tee is a black iron fitting that I found and painted in 1966, and is the only original part of the mount that remains. The counterweight shaft is 1 1/2" pipe for a simple reason: It's a little less than 2" outside diameter, and standard bench-press weights have a 2" center hole and will fit on it. A 2" shaft collar I scrounged somewhere holds the weights to the pipe, but a very short section of 2" pipe drilled and tapped for a 1/4-20 machine screw will also serve.

There's not much in a Newtonian telescope, really. The main mirror sends light up to a smaller mirror at the opposite end of the tube, which reflects the light cone at a right angle through the wall of the tube and into the eyepiece holder. This smaller mirror is called the diagonal, and is held in place in a block suspended from four thin vanes of metal under tension. It seems nonintuitive, but having the central diagonal mirror does not cast a black spot in the center of your visual field!

The "spider mount" shown below is hand-made but took some lathe work. However, I made a similar one in 1966 using nothing but a hand drill, and it worked beautifully.

The tube saddle is Home Depot oak wood with a single length of nylon strap looped around the tube to hold it in place. There isn't even a radius cut in the wood; I simply calculated three points of contact for the 10" diameter vent pipe and arranged the side pieces so that the saddle as a whole "grips" the tube at those three places.

The main pyrex glass mirror is held in place and adjusted in a mirror cell, which sounds grander than what it is: A spring-tensioned tilt-table made of scrap plywood, hardware store shelf brackets, and three springs that (in my case at least) came out of the focus yoke of a biggish 1950s TV set. (Ace Hardware still carries serviceable springs in their wonderful little plastic drawers of odd parts.) Three rubber bumpers glued to the plywood disk support the mirror, which is kept from moving sideways by three flat brackets bent slightly in a vise at one end, and padded with cloth bandage tape.

Three 1/4-20 flat-head bolts are attached to the plywood disk 120 apart and about 1 1/2" in from the edge. The bolts pass through the springs and the holes drilled in the aluminum sheet base plate. 1/4-20 wing nuts hold the cell to the base plate, and allow the tilt of the mirror to be adjusted fairly precisely.

Below is a photo of a mirror cell for a 6" mirror, which I made for a friend using scrap Masonite. You can get a better view of the springs and tilt bolts without the mirror. The three brackets that hold the mirror in place horizontally are not shown, but you can see the three sets of holes where they were later attached. The mirror rests on three rubber garden hose washers glued to the masonite disk:

A decent 8" F8 parabolic primary mirror will cost you from $200 - $300 depending on what it's made of and how accurate the curve is. The whole telescope should come in under $500 if you shop well and use scrap lumber and metal where possible.


The Lane Tech High School 8" F8

Once I got into high school, I immediately joined the Lane Tech Amateur Astronomical Society, and discovered that whereas the club did have a completed telescope, all that existed was the tube assembly and optics. They had been given some odd bits toward a mount, but nobody there knew enough to put it all together. So bang! I decided to build on my experience and finish the club scope. Here it is, and by now some parts should look familiar:

 

 

I hadn't taken machine shop yet (that would come the following year) but once I had the design sketched out, one of the other older members of the club did the machine work. The three brown rods are actually 1" threaded steel from somebody's scrap pile, screwed into three pipe plugs drilled and tapped with the same thread. They allowed precisely leveling of the mount, though they were a couple of inches too long. The 1 1/2" cold rolled steel polar shaft was turned down to 1/2" at the end to accept a worm gear and thus be motor-driven to follow the rotation of the Earth. (Alas, as best I know no one ever finished the motor drive.)

Whewn the photo was taken the mount was complete but needed some tweaks: There was no brake on the polar shaft, and the vertical pillar was about eight inches too high. Both problems were eventually solved. I don't know whatever became of the scope, but I hope it's still at the school somewhere, even forty years on.


The Turn-on-Threads 8" F8 Porter Springfield

This one is a little bizarre. In 1968, after I had replaced the square plywood tube with the spiral aluminum one, I had this square plywood tube in the corner of the basement. During one fevered summer week between sophomore and junior years of high school, I attempted to turn it into a Porter-Springfield mount. This is a brilliant if problematic way to mount a telescope such that the eyepiece never moves, regardless of where the telescope is pointing. It's a tough thing to explain. First, look at the scope as a whole:

Now, take a look at a closeup of the eyepiece section at the center:

 

 

(These are the only two photos that have survived.) The heart of the mount is a 2" iron pipe cross, which turns on the threads of the 45 street elbow (here, painted black) atop the galvanized pipe vertical pillar. Inside the center of the pipe cross is a small diagonal mirror, which turns the light cone up to an eyepiece mount (look for a glint of brass.) The telescope thus has two secondary mirrors: one in the conventional Newtonian position at the center of the tube assembly, and a second inside the pipe cross. No matter which way the tube points, the light cone is reflected first into the center of the pipe cross, and then up to the eyepiece. (See if you can rotate the two scope axes in your head to envision what I mean!) In use, the observer looks comfortably down into the eyepiece (here a black cylinder above the brass sleeve) and never has to crane his neck.

This mechanism was invented by the legendary Russell W. Porter in 1920 or so, and while brilliant, it has drawbacks: Balancing the tube is diabolical, and yes, that is an old TV power transformer tied to the balance assembly. It worked, but the pillar was too tall and too wobbly (such things should be built from stouter pipe and set into cement bases) to work well. It was, however, the best that I could do at 15 with little money and in truth not a lot of skill. It may be the only turn-on-threads Springfield pipe mount ever attempted, and (I guess) I'm proud of that, even though I never used it very much, and abandoned the square tube entirely soon afterward. I was in the thick of another project by that time, and by junior year was pouring everything I had in time and money into it: A 10" F6.7 Newtonian scope, for which I ground and figured the primary mirror all by myself.


The 10" Newtonian F6.7

And oh my lord, what a project it was. I had begun it during my sophomore year at Lane Tech, by purchasing a 10" Edmund Scientific mirror grinding kit from a friend of mine, who had bought it for $40 and, after discovering that he did not have the time or equipment to finish it, sold me the works for $10. (Remember, this was 1968, when $10 was actually big enough to matter.) I started grinding it in the basement, atop an old and defunct wringer washing machine. However, the further along I got, the more I felt I would need help, and in the summer of 1968 I enrolled in a mirror-making class at Adler Planetarium on the Chicago lakefront. That was an act of consummate wisdom, as polishing and figuring mirrors is not something easily done in the basement without certain gear that I was too poor to buy and too dumb to make. And so I spent the entire summer of 1968 running down to Adler all by myself on the subway, endlessly stepping around a water-filled 55-gallon drum, scraping one glass disk over another with a water slurry of carborundum in between, and taking abundant advantage of the on-staff expert assistance.

It was a huge project for one so young (I didn't even have a driver's license at that time) but I saw it through, and by late August it was finished: A 10" F6.7 mirror figured to an astonishing 1/20 wavelength accuracy, aluminized and ready to use. Alas, I did not have a telescope to put it in, as all my time had gone into creating the mirror. So it was almost another whole year before I managed to score a tube, bearings, shafts, and other parts and get them all pulled together into workable form. The scope saw first light right before Christmas 1969, and the photo below is from January 1970:

Here's a closer view, on that same day, this time with me at the eyepiece:

The mount was not entirely finished at this point. I had not created a friction brake for it, so the friction came from jamming pieces of scrap plywood and masonite between the equatorial head plate and the 2" steel polar shaft. Remarkably, that haywire system worked well, but if the scope were spun too quickly in right ascension, the rapid movement of the polar shaft would kick the plywood out of its place, and the now-freewheeling scope would keel over and whack me in the head. (This happened more than once.)

The triangular wood base was peculiarly effective, and interesting because when I designed it, I was assuming that it would be used as a cement form allowing me to pour a concrete base. (I hadn't calculated the weight of such a thing, and so did not realize that I would not have been able to move it once it was cast.) However, the triangle (made of scrap 2 X 8s) was so heavy and sturdy all by itself that I said what the hell, and just used it as a base and not a form. The wood triangle base stayed with me until 2000 or so, when I realized that a north Scottsdale colony of termites had hollowed it out and ruined it.

In the spring of 1970 I added a polar worm gear and motor drive to the equatorial head. However, I did the figgerin' wrong, and the drive turned the scope the wrong way. That is, the motor drove the polar axis from west to east instead of east to west. It was acutely embarrassing, and surprisingly hard to fix, because I had designed the mounting plates for that particular motor, and then had them welded to the equatorial head. I looked for a motor that would fit "the other way" and never found one. To this day, that scope has never had a motor drove that worked correctly.

 

 

Optically, the scope was (and is) awesome. Mechanically, it has always been a nightmare. I appreciated the importance of rigidity and mass in telescope mounts, but I was also constrained by what materials I could scrounge at school. The equatorial head was made of 1/2" scrap steel plate, and 2" solid cold-rolled steel shafts turning in brand-new ($20 each!) Fafnir pillow-block ball bearing assemblies. The head assembly alone weighed 120 pounds without the declination shaft, and was pure murder to haul around.

Development on the scope slowed down radically after I graduated high school, because I no longer had access to machine tools for working steel and brass. I got a lathe again in 1978, but by then I was a little burned out on the big scope, and didn't add much to it as the years went on. I worked on the tube and optically assembly here and there, and converted the tube from aluminum to wax-impregnated Sonotube concrete form in the mid-1970s. I covered the Sonotube with yellow ConTact paper because no paint would adhere to the wax coating.

I still have the 10" scope, and in 1999 I began work on a poured concrete pillar to replace the termite-eaten wooden triangle base. What I did is dig a biggish hole in the desert caliche (a chalky stone that underlies a thin layer of dry soil in the Sonoran desert) and used an inverted plastic bucket that had once held swimming pool chlorine tablets as a cement form. Pete Albrecht helped me pour it, and we embedded an electrical junction box and three stainless steel bolts in the concrete. Later the bolts allowed us to attach the new equatorial tang, which was an aluminum casting poured in a local foundry and machined on my lathe.

It was beautiful. (It helped some—nay, critically—that Pete is a mechanical engineer.)

Working with all this massive metal was a trial at times. By 2002, I was 50, and not the muscular stud (ha!) I had been in college. Below is a photo of me trimming up the 60-pound equatorial head base plate that I had created in high school, so that it would fit the new aluminum pier and tang. Man, that was a job. My back hurt for weeks. Carol says, however, that I was wearing the face mask in the wrong place...

I got some good use out of the scope in the years 2000-2002, until my publishing company imploded and we left Arizona for Colorado Springs. It was much easier to deal with a permanent pier installation, and after I removed the tube and saddle from the mount, I threw a cheap plastic trash can over the equatorial mount and pillar to keep what little rain we received off of it.

It's hard to see the details in the polar gear, so below is an enlarged copy of that portion of the equatorial head. There's a bronze 96-tooth gear on the end of the polar shaft, with a three-point friction brake holding it in place. This allows you to move the telescope without stripping the gear teeth: A small bronze plate "squeezes" the big worm wheel against the machined end of the steel polar shaft. The worm wheel thus is not pinned or set-screwed to the polar shaft. Move the telescope, and the brake slips, but move the worm wheel slowly, and it will drive the telescope in right ascension.

An aluminum handwheel allows you to move the polar axis in finer increments than simply shoving on the tube. The four empty bolt holes used to hold a second pair of pillow blocks and a second stage of worm gear reduction, with a synchronous motor hanging off the right end of the shaft.

I had cornered an odd but powerful geared-down stepper motor in the summer of 2002, with the intent to couple its driven hub to the small shaft, right where the handwheel is in the photo. Alas, life got lively about that time, and the stepper motor is still in a box.

I will admit with some regret that I have not had the 10" scope assembled and working since we moved to Colorado in early 2003. I don't have a place to put a concrete pier, and the energy and time to re-create the late wooden triangle base have escaped me. It's just easier to use that junky old turn-on-threads 8" scope that saw first light in 1966.


 

Brian's 6" Newtonian

When my older nephew Brian got to be 13 (1996) he expressed some interest in building a telescope. (We do not have children of our own.) He and his brother would come out to Arizona every other year, and we would always tackle a build-it project together. The telescope was very simple, and it drew on the design of the original 8" I had begun in 8th grade thirty years earlier in 1966.

It was a 6" Newtonian, which made it much smaller and lighter (and easier to wrestle with) than even the 8", and for starters it's not a bad size. I ordered the tube and all the optical path parts from ads in the back of Sky & Telescope Magazine, and Brian and I put it together over a week of hot afternoons in the summer of 1996. The photo here shows the scope mounted on the 2" pipe pillar I had sunk into concrete back in 1990 and otherwise used for my 8" scope. A 2" pipe pillar is big enough for either a 6" or an 8" Newtonian; it's not rigid enough to hold the weight of an ambitious 10".

The simple tube saddle is made of particle board, one slab in the center with a pair of slabs cut to fit the curve of the tube on each end. The blue band is nylon strap from a camping store. All the rest of the base are 2" pipe fittings identical to the ones I used on my 8" scope. The photo below is a little awkward, but it shows very clearly how the mount goes together. The black fitting is a 2" black-iron floor flange that I had in the junkbox, but galvanized flanges work just as well, and are easier to find.

It's a great little scope, and I am very proud that Brian still has it and still uses it, even though he's now a banker in downtown Chicago helping cut deals that run to nine figures with monster corporations. Kids love building things. They grow up so fast. Don't let the chance go by.


 

The Enlarger Lens Altazimuth

This was an experiment, and another joint project , this time with my younger nephew Matt. Carol's father had left us an old but intact enlarger lens assembly when he died in 1990. I had it on the shelf, not sure what to do with it, but itching to see if it could become the front end of a telescope. In 1999 Matt and I decided to give it a go.

It's all junkbox stuff and telescope leftovers; the focusing mount was the very first one I had bought with my allowance at the American Science Center in Chicago in 1966. The lens is attached to a black PVC toilet mount flange with a plumbing squeeze clamp exactly for that purpose; miraculously, the enlarger lens was just a little smaller than the toilet flange. (Sometimes you get lucky. That would have been a tough nut to crack otherwise.)

The photo below is the telescope with the big lens tipped forward so that the prism is visible. The right-angle prism was a surplus item (marked "Eastman Kodak") that I had bought on spec at a hamfest. The prism mount is crude but it worked. The rest is scrap particle board plus a couple of pieces of scrap oak.

There was originally a baseplate, also of scrap particle board, on which the assembly shown above pivoted on an inexpensive Home Depot lazy susan bearing. The baseplate and bearing plate got soaked with sewage during a plumbing malfunction in 2006 and had to go.

How was it as a telescope? So-so. The exit pupil is too big and there are mondo color fringes on bright stars. The Moon looks great, though, and it works tolerably well as a terrestial scope, if you can get past the fact that the field is reversed right-for-left. I may have done something wrong, but then again, enlarger lenses are not designed to focus at infinity so I shouldn't expect perfection. It was a quickie project to prove a hunch, and for that it worked just fine.


 

My Recommendations

A 6" Newtonian is easy to build, quite light, and relatively inexpensive. It's a good size for a kid project treated as a project and not a passion. However, if astronomy is your passion, go for an 8". Your light gathering power (which is what matters in telescopes like this, not magnification!) is almost twice what it is in a 6" scope (compare the surface area of a 6" mirror to an 8" mirror) and yet neither size nor weight increase by a factor of two. An 8" Newtonian can be mounted on easy-to-get 2" pipe fittings and pipe sections, which are the largest size you can typically get without special ordering.

You might well wonder if it's then not better just to scrape up the cash and buy a Meade GPS or one of the Celestrons. You get computer control, a more compact physical design, and (as my friend the well-known astrophotographer Michael Covington once told me) you will spend less time looking for things and more time looking at them. (Finding faint celestial objects with a pipe-mount scope is an art in itself.) And that's true: With a Meade you can basically say, "Go find M31." If M31 is above the horizon the motors will begin turning, and when they stop, M31 will be in the eyepiece.

On the other hand, when you work through Sam Brown's All About Telescopes and piece the instrument together all by yourself, you will know how it works. Intimately. You will learn a great deal about nuts, bolts, pipe fittings, and hand tools. And when it's done, you will line up the Moon or Saturn in the eyepiece, steer your friends or significant other in front of it, and listen to them gasp with astonishment.

Junk? Sure. Effective? Until you do it yourself, you have absolutely no idea!


 

 

 

 

 
 

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