alt-az, company 7, equatorial, hands-on-optics, plywood, teflon
7. Build the scope
A. There are many, many books and articles and websites devoted to the many, many ways of building your telescope tube and mount. We have quite a few of these books in our library, and you should definitely study them! In addition, public star parties put on by NOVAC, NCA and other local clubs often have home-made telescopes on the field, and you can ask the makers of those scopes how they did it. Fortunately for us, John Dobson came up with an excellent way of making inexpensive, easy-to-build and easy-to-use telescopes of the Newtonian model, even if he was a nut-case. Willmann-Bell publishes quite a few such books.
B. I strongly recommend an alt-az telescope mount for visual use, rather than an equatorial mount on a pier made of plumbing parts, as people used to make in the 1940s through the 1990s. (As noted earlier, if you want to do astrophotography, you will need a much more complicated and much more expensive mount that tracks the stars precisely. Building such a mount yourself is exceedingly difficult and requires precision machining and electronics!) Most important: plan to make a telescope that is easy to use and not too complicated to build! Using slight modifications of existing plans is much easier than trying something completely novel in design. If you strive for originality, you can be sure that you will need to modify and re-build parts of your invention, perhaps several times, because of problems that you didn’t consider or notice originally. (Think about what a nightmare it would be to drive a Model-T Ford automobile, the first real mass-production car, with all of its nutty and dangerous defects, compared to the comfortable and safe and reliable car that people drive today!)
C. I have a set of plans for a simple 6” Dob on this very blog. (Click for link)
D. At the CCCC, we also have a fairly decent set of hand and power tools for working with wood and metal, so you can make the rest of the telescope here if you like. Be careful, and follow safety directions!
E. We even have a wonderful assortment of ‘oops’ paints from hardware and paint stores, if you don’t mind the ghastly colors.
F. You will need at least half of a sheet of 4’ by 8’ plywood for the scope. The plywood can be any type you like, but don’t get a sheet that is warped or wet or too thin. Nice plywood like Appleply or Baltic Birch can be expensive, but it is strong and looks quite beautiful when varnished. Three-quarter inch thickness is standard, but it’s generally sold as a weird number like 23/32”.
G. You will also need the following commercially available items, some of which we usually have on hand, marked by “UOH”.
- Diagonal secondary flat elliptical mirror (we have a few)
- Secondary mirror holder
- Finder scope(s) (I recommend a 1-power finder like a Telrad or a Red Dot finder, as well as another finder scope that magnifies about 5 to 10 times)
- Possibly a Barlow
- A few pieces of Teflon UOH
- A few square feet of Formica or the equivalent UOH
- Miscellaneous screws, nuts, bolts, screws, glue UOH
- Guidance UOH
- Paint UOH
- Random wood scraps, including a short 2-by-4 UOH
- For the mirror holder, you need: Three compression springs; 3 flat-headed machine screws; 9 washers; 3 wingnuts; and a small fresh tube of pure-silicone caulk or aquarium cement
H. We are very fortunate to have a local specialty store that sells telescopes and accessories to the public, called Company 7 . It’s located near Laurel, MD and has an amazing display of rare telescopes. Please shop there! (In other words, don’t talk their ears off getting their advice, and then order an item online because it’s a few dollars cheaper!)
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