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Telescope Making for the Relatively Unskilled


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Telescope Making for the Relatively Unskilled

I would have liked to title this article “Telescope Making for Dummies” but I didn’t want to get sued. Other titles that came to mind were “How Not to Build a Telescope” or “How to Build a Telescope without Really Knowing What the Hell You’re Doing”, but I decided that the former was too negative and the latter too wordy. Also, this is definitely not a “How To” in the sense that I’m going describe where every nut and bolt goes. There are plenty of good books, magazine articles and websites that already do that, chief among them being Cloudy Nights. My own just completed 12 ½” F/5.2 Dobsonian Telescope is based in large part on Gary Seronik’s “Telescope Making” articles in Sky and Telescope and his own website so there is nothing really original here that hasn’t been covered before. The overall theme which I would like to impart is one of encouragement for all those without the skills of an ace machinist or master carpenter, if the only woodworking tools in your basement are a couple of basic power tools and even if, like me, you have no real experience.  Now I have built a telescope before but it was 50 years ago when I was a kid. It was a 6” F/8 square plywood tube Newtonian on an equatorial pipe mount and my father wouldn’t even trust me to use his circular saw fearing I would maim myself so he made the major cuts in the plywood for me. Then 15 years ago I converted that same scope to an Alt-Az wooden mount based on Richard Berry’s book, “Build Your Own Telescope.” That then is the sum total of my astronomical construction experience…not very much.

So regardless of the lack of tools, skills or experience, if you would like to build a great working, highly functional telescope with your own hands, you can do it, without too much difficulty and the journey will be lots of fun. I also wanted to write this article for another reason. Throughout the construction, I had a number of good ideas and a lot of bad ideas so in case I lose my senses completely and attempt to do this again someday, I’ll be able to refer to something besides my own memory.

 

Planning and Tube fabrication:

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I knew I wanted to make a 12 ½” Newtonian telescope right from the start. 12 ½” has been described both as the smallest big telescope and the biggest small telescope there is and I didn’t want one so large that its size would discourage me from using it. Also I don’t drive an SUV so I couldn’t haul a huge concrete form tube or 4x8 plywood sheets home and I also figured that if I would ever have the inclination to view from a dark site away from home the whole contraption, when broken down into what I figured to be three parts, would have to fit into the trunk of my car and the interior which is 4’ wide. With pencil and paper I estimated a 12 ½” mirror with a 60” focal length would be about right so I worked out some detail plans with Microsoft Visio all the while keeping on the lookout for a mirror. Lo and behold, after only a couple of weeks an F/5.2 premium mirror came up for sale in the Cloudy Nights “Classifieds” section so I jumped at it.

With a bit more calculating, I figured that a 4 foot long, 14” diameter cardboard concrete form tube, the kind sold at Lowes and Home Depot, would be about right. For some unknown reason though, neither store stock a 14” diameter tube but Lowes ordered one for me which turned out to be GOOD IDEA #1 because the ones in the other sizes they actually had in the store had evidently been there for quite some time and were all misshapen and damaged. By ordering one from Lowes’ customer service desk, I got a pristine, just off the assembly line “Quikrete” brand tube that was almost perfectly round with no dings or blemishes. This really wasn’t my own good idea, it just was dumb luck. So with the mirror and tube in-house, I got to work.

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Sloppily Applied Bondo & First Attempt with the Router

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It was recommended on the Cloudy Nights DIY forum that the spiral seam in the cardboard should be filled in with Bondo.  In my opinion, this was BAD IDEA #1, mainly because it didn’t work, at least for me.  I spackled the Bondo on like I was filling in the dent on a car, which is what Bondo is really for, and no matter what I did or how much I slathered on the seams still showed through.  I would apply, wait for it to dry then sand. I did this two more times to no avail. I concluded that the only way to apply the Bondo so that the seams were totally invisible would be to trowel it onto the entire tube thickly. So I decided, in the interest of weight saving, the heck with it, who’s going to notice spiral seams in the dark anyway?

I understood all along that I had a weight issue with a domino effect of one thing affecting another thing and so on and so forth. Solid tube Dobsonians are heavy and they’re designed to be that way. Unlike modern, lightweight and portable open “Truss Tube” telescopes that weigh 30 lbs. or less, my scope tube assembly alone was going to come in at around 60 lbs. Add another 30 lbs or so for the base and rocker box and this scope would be a beast.  While the extra weight would mean more stability and smoother motions in altitude and azimuth (as I read) I knew there would be a limit as to how much I was willing or even capable of lifting, and a heavier tube would mean the balance point of the scope would end up more towards the middle of the tube assembly rather than at the back. Now follow along the thought process here. This then meant that the rocker box would have to be taller to allow room for the bottom of the scope to have clearance when pointed straight up making it even heavier. By minimizing the weight of the tube as much as possible, the center of gravity would fall more towards the rear of the telescope thereby reducing the size and weight of both the rocker and mirror boxes and also result in a savings of material and cost. I created a Weight & Balance Excel spreadsheet and saw that if my weight estimates of the wood, tube and all the components were correct, the center of gravity would end up about 12” from the rear end of a 16” long mirror box, which was just where I wanted it.

Weight & Balance Worksheet: First you pick a reference point, called the “Arm”. It can be anywhere on the telescope but I picked the very front end of the tube. Then you list all the components and their individual weights and note the distance of each component from the Arm. You multiply the weight of each times the distance from the Arm and you have the “Moment”. Finally, you sum all the Moments and divide the total by the total weight and you end up with the location of the balance point shown as the distance from the Arm (indicated by the▲). The actual balance point ended up almost exactly where predicted

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I then fabricated, out of some 3/4” marine grade plywood I had lying around, a tube flange for the top end of the tube, important because it would give the cardboard added support and help keep the tube round, especially crucial at the top where the focuser and diagonal mirror were to be mounted. That turned out nice, mainly because one of my sometime golf partners gave me his router, an ancient Sears Craftsman model that when switched on registered at roughly the same decibel level as the lit afterburner of an F-15. (I bought some ear plugs.) I made a circle cutting jig out of scrap hardboard and totally surprised myself by how well I could cut absolutely perfect circles. My golfing buddy also included some cutting bits, and the ¼” straight bit was the exact thickness of the cardboard tube. So after measuring the circumference 15 different times with a cloth tape measure (“Measure 15, cut once” – my motto) and divided by π to get the correct diameter I routed out a ¼” wide channel in the flange into which the top end of the tube fit perfectly.  I then made a 16 ½” square bottom flange as well that fit snugly around the outside circumference of the tube. GOOD IDEA #2: You need to get and learn to use a router in order to make a telescope.


Next on the agenda was adding some fiberglass to the top 10” and bottom 8” sections of the tube. I was obsessing over the fact that with the tube being cardboard it could warp or deform not only at the top end but also at the bottom which was where the major stress point of the whole assembly would be, the spot where the bottom tube flange attaches to the mirror box. I calculated that a 9 lb tube plus the weight of the additional components, all  hanging out in front of the attachment point, would be  9 lbs X 2’ (the middle of the tube) + 3 lbs X 4’ = 30 foot-pounds of weight on that connection spot. I’m no engineer but to me that seemed like a lot, thus I felt the need to make the cardboard a little more rigid.

At this point the ends of the tube are wrapped in Fiberglass (mixed in with grass cuttings from my lawn) and then spray-painted with primer.

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From a hobby shop I bought some fiberglass cloth and resin, the kind used for making model airplanes. BAD IDEA #2.  This kind of fiberglass cloth is very light and thin…good for model airplanes, not so good for strengthening a cardboard tube. The instructions for the fiberglass said to apply it when the temperature is above 75°. My basement is a pretty constant 63° year-round but it was August and outside it was 95° in the shade. Cindy, my wife, was appreciative of this. She’s basically a nut when it comes to chemical smells (“You’re bringing carcinogens into the house!?!?!”) so working outside spared me her wrath. But this turned out to be BAD IDEA #3. As I said, it was a 95° the day I decided to do this and breezy to boot and my lawn guys had just finished their weekly cutting. I set up two aluminum lawn chairs under the shade of a large Poplar tree in my backyard with an 8’ long 2x4 suspended between them, through which I had inserted the tube. I mixed up the resin and epoxy binder as per instructions, wrapped the cloth around the tube and started to apply the mixture over the cloth. This turned into a total and complete mess! The lightweight model airplane fiberglass cloth kept slipping off the tube and onto the grass before I could apply the epoxy. I then tried to apply the epoxy first and lay the cloth over it. That didn’t work either although some of it finally started to stick but when the epoxy started to set up, which it did very quickly in 95° heat, there were wrinkles, bumps and bubbles throughout the fiberglass cloth. Finally, to top it all off, a gust of wind came along and caught the center of the tube perfectly. It "weather-vaned" - and everything - tube, 2x4 and the lawn chairs blew over onto the freshly cut lawn!  The end result was a fiberglass coated tube with a million, more or less, individual blades of cut grass impregnated into the side. Beautiful, just beautiful.  If the tube looked like crap before the fiberglass, it really looked like garbage now.  

4 coats of Rustoleum primer, sanded with 120, 240, 330 and 400 grit sandpaper, topped off with Rustoleum Blue Metallic paint, and it still looks like crap. The spiral seams still show and the Bondo did nothing. In fact, it made it worse because the tube has acne like blotches all over.

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Before the fiberglass set up, I tried to pick out as many of the blades of grass that I could with my fingers but in the heat it hardened quickly after which I sanded the tube, getting it as smooth as possible, which wasn’t very smooth at all. The next day, I tried again with a second layer of fiberglass. Fortunately it wasn’t windy, it was slightly cooler and I secured the 2x4 and the lawn chairs better than the previous day. It went on a lot easier than the first layer, but in retrospect, a heavier weight fiberglass cloth, applied in smaller pieces, would have been better.  Later on I saw a YouTube video of a guy making a fiberglass sink. He used heavyweight cloth cut into smallish pieces with tons of epoxy resin. That’s the way to do it I suppose. Maybe I should have watched that video first?

The last stage of the tube preparation was painting, this time with many, many cans of Rustoleum; The inside of the tube got two coats of black chalkboard spray paint and the outside four coats of sandable primer then 2 coats of metallic blue. Again, due to the fumes, I was banished outside. With all the sanding of the primer plus the coats of paint a majority of the grass clippings were concealed. Regardless, I ended up with a pretty lousy looking tube due to my cruddy Bondo job, the blotchy application of the fiberglass and 1 million impregnated grass clippings. But none the less it was one that I thought could be functional.

 

Carpentry – Mirror Box and Rocker:

The mirror box and rocker are made out of Baltic Birch, a high quality imported plywood that is not sold by Home Depot or Lowes. It comes in 5’ x 5’ sheets (1325 centimeters) but I found out that not very many lumber yards carry it. Since I don’t own a table saw, and by experimenting on some scrap plywood with both my circular saw and saber saw I discovered how impossible it would be for me to make cuts that were anywhere close to straight and perpendicular, I decided to farm out the major cutting to a professional. This was GOOD IDEA #3 and the best of all my good ideas.

Cut-List Diagram (Click on the image to launch a larger version in another tab.)

 I drew out a cut-list diagram in Visio and visited a couple of local cabinet makers.  One highly automated woodshop wanted $75 per sheet for the wood. I would need to buy two sheets; one sheet of 5/8” and a half sheet of ¾”, plus $300 to make the cuts on a CNC machine.  I discovered another much smaller cabinet maker located not far from where I worked so I paid a visit and showed him my design. He surprised me by saying he knew exactly what to do and how to do it since from his point of view all I needed were a couple of boxes. He didn’t have a CNC machine but showed me some of his work, all of which was done the old fashioned way with jigs and a table saw. It looked extremely good to my eye but here was where I got really lucky. Sitting in the corner of his shop he happened to have a 3 foot high stack of 5/8” Baltic Birch pieces left-over from old projects. I asked him what he was going to do with it and he said, “Probably nothing”. After sorting through the stack we both realized he had more than enough in sizes large enough for what I needed. So we made a deal. He provided the Baltic birch out of his scrap pile for basically nothing and made all the major cuts for me for less than half of what the other shop wanted. The result was beautiful; straight precise cuts and everything at perfect right angles. Not in a million years could have done this with the tools I have.

Once the wood was back in my basement everything went together very nicely, mostly because of the precise cuts my cabinetmaker made but also due to the router which was invaluable in making perfect dados for the joinery and enabled me to round-over all the corners and edges.  In this, You Tube was my friend.  I watched several and one showed me how to make a router table that I could mount my router to from underneath and clamp to my workbench. I glued everything together (lots of clamps) and then  started sanding, ….and sanding and more sanding, first with 60 grit sandpaper before the gluing then again with 120 grit after. I continued on with 220, then 330. Finally I applied Miniwax Clear Varithane (all the while my wife yelling at me, “CARCINOGINS”!!!). Then there was more sanding, two more layers of Varithane with sanding in between and finally a coating of Miniwax Wood Finish Wax with a final buffing with #000 steel wool. At the end of all this, my wood was baby butt smooth.  The overall carpentry was gorgeous but the fact of the matter is the finishing of the wood took a lot longer and was much more work than the actual carpentry itself. Moral: If you don’t have a table saw you must farm out the major cutting to a cabinetmaker.

I decided to stain the two semi-circular altitude bearings with a walnut color to offset the clear finish of the mirror box. BAD IDEA #4 – Don’t Stain! The wood stain did not go on evenly. Cindy charitably told me “it has the distressed look.” In reality it was blotchy and uneven so it perfectly complimented the crappy look of the tube.

 

Plastic Laminate Bearing Surfaces:

As we all know, Wilsonart Plastic Laminate “Ebony Star” is no more. In its place are a variety of different materials to choose from including various plastic laminates from both Wilsonart and Formica as well as something called FRP – Fiberglass Reinforced Plastic, which is only available at the big box stores in 4x8 sheets. According to the DIY forum on Cloudy Nights, Formica “Crystal Finish” (#42) is the next best alternative to the old Wilsonart Ebony Star #50 finish so I began a search. As it turns out, Lowes carries black Formica with the #42 finish, but like the FRP, only in 4x8 sheets, enough for eight or nine telescopes. Since I was only making one, I kept looking. After phone calls to several kitchen cabinet shops in the area I finally found one with some scrap Formica with the Crystal finish. It turned out to be #7743 “Jamocha Granite”. I would have preferred black, but I couldn’t be choosy at this point. They had a 2’x4’ scrap piece that they let me have so I was set. I followed the instructions for the application with contact adhesive (again, I was sent outside) and it went on pretty easily to both the altitude rings and the underside of the rocker box. The Jamocha Granite didn’t look too bad actually and kind of blended in with the walnut stain. The router kit from my golfing buddy included a trim bit, and this – trimming down the Formica to match the edges of the rocker box and the altitude rings, turned out to be the easiest part of the whole project.

 

Assembly:

At this point the most critical measurement I needed to make was to determine the actual focal length of the primary mirror. This is so that I would know exactly where to drill the hole in the tube for the focuser. With a solid tube I would only get one shot at this, so I was a bit nervous. The previous owner told me that he thought the mirror was an F/5.2, but I needed a way to figure out exactly what that focal length actually was.

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I took a cardboard box and cut a small hole in the side where I could insert and secure a small Maglite flashlight with the head removed, exposing only the LED. I then taped a white piece of paper right next to the hole. With the mirror set up on its edge on the floor of my basement I turned on the flashlight pointing it at the mirror and slid the box along the floor backwards and forwards until the reflected image of the LED bulb was in perfect focus on the piece of paper.  I measured the distance, divided by two and found the focal length to be exactly 63 5/8”. Dividing by 12.5 came out to an F/5.09 mirror, not F/5.2. “Hmm”, I pondered. Either the previous owner was way off on his knowledge of his own mirror or I was measuring wrong. So I repeated the above process 3 more times, wrote down all the different focal length measurements I got and then took an average which came out to 63.6563”. I pondered some more…something still wasn’t right.  I posted my problem to the Cloudy Nights DIY forum and received a variety of responses.  Eventually, someone pointed out the reason for the discrepancy – the Bevel.  Mirrors have bevels around their edges. The mirror maker files down the sharp edge so that it won’t chip during the mirror making process. My mirror had a 1/8” bevel meaning that the actual reflecting surface of the mirror was a diameter of 12 ¼. Divide 63.6563 by 12.25 = F/5.196. That was pretty close to what the previous owner thought at which point I felt a lot better. So it turns out my mirror is either a 12 ½” F/5.1 or a 12 ¼” F/5.2, take your pick. The key number though was 63.6563. That’s the total distance in inches from the surface of the mirror to the diagonal mirror then 90° up 7” (half the diameter of the tube) to the focuser. Factor in the length of the focuser travel and the thickness of the tube wall and I had my spot to drill the hole, which was accomplished with a 2 ¼” hole saw.

Once that was done, everything else was a piece of cake. I installed the diagonal mirror in the mirror holder, attached the holder to the spider and the spider to the tube. (Astrosystems sells great components and provides easy to understand instructions.)The fiberglass, while blotchy and pock-marked, provided a nice firm surface for both the focuser and spider nuts, bolts and washers to secure to. I glued the tube to the bottom flange and screwed the bottom flange to the front of the mirror box into 5/16” embedded T-Nuts using Hex Head screws with press-on knobs. (Note: If I ever do this again I should make sure to install the T-Nuts before I glue the mirror box together, not after.)  I then bolted the primary mirror mount to the tailgate on the back of the mirror box, installed the mirror and almost unbelievably, I was almost done!

 

Finishing Up:

The last piece of the puzzle was to determine the center of gravity for the entire upper tube assembly. This was simple; I took a round broom handle and placed it underneath the mirror box then rolled the entire assembly back and forth until it was perfectly balanced at which point I marked the spot on the side of the mirror box with a pencil. As it turned out, the estimate I initially derived from my weight and balance worksheet and the actual balance point were within a half inch of each other.

 

Whoops!

It’s typical of the way I do things that my project was nearly complete with only a few screw-ups when I made a doozy and nearly gave myself heart failure in the process. I attached the first of the altitude rings to the mirror box UPSIDE DOWN. Why? Well, I’ll tell you. The night before I had been refinishing the under-side of the mirror box and had therefore turned it upside down to work on then left it overnight to dry. By the next day I had forgotten that little fact completely.  I then drilled holes and bolted the first altitude ring right-side up to an upside down box!  It wasn’t until that exact second that it hit me!

I cursed and screamed bloody murder at myself and Cindy called down to the basement asking if she should call the paramedics since she assumed I must have cut off a finger, (which I almost did 30 years ago, but that’s another story.) I may have actually fallen to my knees and wept – I’m not sure. I do know I nearly lost my mind. But I calmed down… eventually, composed myself…sort of, removed the offending ring and filled in the three bolt holes with wood filler. I was devastated and thought I had ruined everything because the one thing that looked really good on this scope, the woodwork, now had three unnecessary 5/16” holes drilled into it. As it turned out, after dry-fitting the first altitude ring again, I saw that two of the three holes would be covered up by the ring when mounted correctly and the wood filler did a pretty decent job of concealing the one remaining visible hole. So it didn’t look as bad as I originally thought it would when I went temporarily insane.

The last step was the Teflon. Fifteen years ago I converted the telescope I had originally made when I was 16 from its original pipe mount to a Richard Berry Dob. At that time I had bought 1” wide x 4’ length strips of the stuff and the minimum amount I had to buy was way more than I needed so I saved the extra thinking that eventually I would need it to make another telescope. Well, today was the day. GOOD IDEA #4 – Don’t Ever Throw Anything Away!  I nailed the Teflon to the altitude and azimuth bearing surfaces with brads, hefted the entire tube assembly (boy was that heavy!) onto the rocker box and tested the scope movements. Balance was spot on, the scope stayed where pointed and movements up and down, left and right were like butter. I was thrilled…beyond thrilled, actually. Overjoyed maybe?

 

Conclusion:

Finished! 12/26/2015 – Note the azimuth setting circle below the base and a Harbor Freight digital inclinometer on the mirror box for the altitude indicator.

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Throughout the late summer and pretty much the entire fall, the weather in the northeast was great,  day after day of blue skies and cloudless nights. I had started the build process with the acquisition of the primary mirror in August. I finished up on December 26th. Christmas 2015, the day before, was 65° and sunny and I if I hadn’t been so engaged in a furious amount of telescope making trying to finish up, I could have played golf, it was that nice.   December 26th was cloudy and warm but then a cold front moved through that very afternoon. The rest of December reverted to typical New Jersey winter weather, the three C’s; cold, clammy and cloudy. I waited, impatiently, for a clear night.

After a week of solid clouds night after night, finally I was able to get a look though my new scope. It was really frigid so I didn’t spend hours and hours outside, but it was just long enough, maybe 90 minutes, to get a good look at the great nebula in Orion, the Andromeda Galaxy and its companion, the Ring Nebula and even M81/M82. Everything came to sharp focus, movements in altitude and azimuth were smooth, yet when changing eyepieces the scope stayed put, and stars were sharp bright pinpoints of light. Needless to say, I was delighted and actually surprised that it everything worked so well.

 I’ve since added a few enhancements; Knobs to replace the bolts for collimating the primary mirror and some wheelbarrow type handles and wheels, so I can move the scope without killing my back, were the first things I added. I have since spent many happy nights this past year at the eyepiece of what I consider to be a premium telescope that I made myself.   Telescope making is something anyone can do. After all, if I can do it, with minimal tools and few if any of the skills to use them, plus a little bit of patience and the ability and desire to reference the many sources of information available both on the Cloudy Nights forum and elsewhere, anyone can build a telescope that will work extraordinarily well.

 

Editor's Note:

The author has graciously shared the Excel Workbook that he used to predict the center of gravity for his dob as well as the Visio drawings of the design used in this project.

Some notes from the email exchanges we had on this might prove to be helpful:

"As requested, attached is the original Visio file of my drawings as well as the “Weight & Balance” Excel worksheet. If I had known you had Visio I could have submitted everything separately. As you’ll see. There are 4 tabs including the Cut List plus another drawing of some folding wheelbarrow handles I’ve added which I didn’t include in the original. I’ve also cleaned up the main drawing since the original version, which is the one I embedded, because I started writing the article many months ago but continued to revise the drawing."

"You can play around with the Excel worksheet if you want by changing the numbers in the yellow boxes. If you do you’ll see the little triangle that indicates the center of gravity move around. I actually have a box captioned “Extra Wgt” which I left at zero that you can adjust then set back to 0 when done. I thought I might need to add weight at the back end of the scope but when I got the mirror, it was so heavy, extra weight wasn’t needed. I’m actually kind of shocked that the thing actually predicted, within a tiny fraction of an inch, where the CG would be but I needed to do this before I bought any lumber to figure out how much I would need and what size everything would need to be. I looked up all the weights of the components on-line as well as a pounds per square inch figure from a Baltic Birch lumber distributor before I settled on the overall design and bought anything (other than the mirror). That’s a detail I could have expanded on in the article but felt that it would be a bit too much."


Download the Visio Drawings

Download the Excel Workbook

 


  • Charlie Hein, CollinofAlabama, okiestarman56 and 16 others like this


15 Comments

Greetings, xrayvizhen; nice article!  I like the detail you present and the anecdote regarding upside down assembly “Whoops!”  Many builders, especially novice, are so concerned about the possibility of screw-ups, that they never get started.  Best attitude is to be careful and accept that mistakes happen and best we can do is to mitigate/correct.  I fondly recall building scopes up in my parent’s attic with precious little $ and only hand tools.  Even the smallish mirrors, walking around an oil drum.  Now I’m working on a 36-inch… yep…  hoping to have it operational in about 6 months.  Something positive about savoring the view thru a telescope that you built yourself!  PS My 1st mirror 8”… I got it done and admiring it, dropped and broke it …  Gave up for 6 months then built a nice 6-inch scope!  Tom Dey

Greetings, nice article! Where did you get a 12.5" f/5.2 mirror?

Greetings, nice article! Where did you get a 12.5" f/5.2 mirror?

Hi Augustus - as I wrote in the article, it appeared in the Cloudy Nights "Classifieds" section. I was just about ready to buy a new 12" F/5 GSO mirror set from Agena Astro but was procrastinating, when all of a sudden, there it was...at a very good price and the previous owner threw in the mirror cell also. The fact that it was a premium 12 1/2 from the 1990's, 2" thick pyrex weighing 25 lbs actually helped me avoid some balance issues that would have occurred with the lighter GSO mirror.

    • Augustus likes this

 

Greetings, nice article! Where did you get a 12.5" f/5.2 mirror?

Hi Augustus - as I wrote in the article, it appeared in the Cloudy Nights "Classifieds" section. I was just about ready to buy a new 12" F/5 GSO mirror set from Agena Astro but was procrastinating, when all of a sudden, there it was...at a very good price and the previous owner threw in the mirror cell also. The fact that it was a premium 12 1/2 from the 1990's, 2" thick pyrex weighing 25 lbs actually helped me avoid some balance issues that would have occurred with the lighter GSO mirror.

 

Cool. I am considering making a 12" Dob next year and found your article very helpful.

Thanks for sharing this with us!

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Soarrunwalk
Dec 07 2016 09:55 PM

Ditto - thank you for sharing!

 

I appreciate your writing style and the fact you took the time to put this together for us to learn from and enjoy.  Many clear skies to you!

Thanks for the nice comments.

 

This article as written before I submitted it to CN was originally a lot funnier, mainly because of the language that spewed out of my mouth before, during and after the screw-ups occurred and just the plain dumbness of some of the things I did or didn't do or didn't even anticipate. While not "R" rated, it was definitely PG-13, and definitely more entertaining. However, somewhere along the line, I decided to tone it down and make it more "family friendly" and figured that some ignorant soul out in the world not yet familiar with this rather bizarre hobby of ours might want to do a google search about telescope making looking for some true life experiences and would stumble upon this. The result may not have been as humorous as originally written but might be a little more valuable to them.   

I know the feeling. Built many scopes, observatories... each with its own humiliations and triumphs. The reward is when you get to the eyepiece and IT WORKS!  Tom

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jhayes_tucson
Dec 18 2016 11:46 AM

That's a very nicely produced article with a lot of useful information, nice diagrams, and good tips!  Well done.

 

John

Great article (even in the family friendly version)! We have highlighted this as the "Link of the Month" at the Stellafane Links page, thank you for taking the time to write it for future generations of telescope makers. Jay

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John O'Hara
Dec 27 2016 07:10 PM

What's the thickness of your mirror?  Did you mount it using RTV adhesive?

The mirror is a full 2" thick pyrex and heavy! When mounted in a standard 9 pt. flotation cell (no adhesive) it and the cell together weigh 29 lbs.

 

I should also add that it's not a total mirror mount. I removed the back part and bolted the front, the flotation part the mirror sits on, to the rear tailgate using the three large collimation bolts. Thus the tailgate takes the place of the rear portion of the mount.

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solarviewer
Dec 29 2016 02:31 AM

Thank you so much for writing and sharing this wonderful article, your hard work is very much appreciated!

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dawsonian2000
Jan 04 2017 06:48 AM

I’ve received several private messages from a few people on CN who have seen some pictures I’ve posted of the telescope I made, which is also my icon picture, and asked if I had a build thread. I didn’t. But all along I had an idea of writing this article because while I have seen many pictures and build threads of outstanding scopes built by people who are obviously either machinists, carpenters or engineers or just very experienced builders with a full suite of shop tools, I am none of those and I only have a couple of hand tools and minimal skills & experience. But I built this thing and it’s outstanding, so I figure that maybe there are folks out in the world who would like give telescope making a try but might be a little intimidated by some of the beautiful work displayed, especially on the DIY forum. This is NOT another “How to Build a Telescope” article. Rather, it’s more of an idea on why I built what I did, some of the planning and thought processes involved and how to get around the lack of tools or skills. (Hint – subcontract the hard stuff.)

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Hi xrayvizhen!

 

Congratulations on a job well done! It is indeed a pleasure to read your article and know that there are others that have the same mindset when it comes to conveying the skills of building their own telescope. The absolute thrill and feeling of accomplishing this effort does more for the spirit than can be imagined; let alone to the many wanting to build their own instruments. I, too, have followed the same premise by showcasing the telescope builds I have completed via a comprehensive and detailed overview of each project on my website: http://www.vega-sky-center.com

 

 

Again, congratulations!

 

Mel

Thank you for the informative and very entertaining article.  I have not laughed this hard in years!  Especially the tube part.  I thoroughly enjoyed it.

Jim



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