The primary reference for anyone in the English-speaking world who wants to build a large Dobsonian telescope is The Dobsonian Telescope: A Practical Manual for Building Larger Aperture Telescopes by David Kriege and Richard Berry. I’ve owned a copy for many years, browsing its pages whenever aperture fever struck. At 475 pages it is a substantial reference and provides detailed information about all aspects of building a specific Dobsonian design — essentially the same scope sold by Kriege’s company, Obsession Telescopes. The book sells for $29.95 and should be in your bookcase before starting on a large dob project.
Despite its value, The Dobsonian Telescope can be an irritating book. The first sentence on the Obsession Telescope site provides a clue as to why: “Are you obsessed with the best? We are.” There seems to be no doubt in David’s mind that his design IS the best and this tone comes through loud and clear in the book, which in places can be dogmatic and/or condescending. The Kriege design has many good points, but it isn’t the only way to build a large Dobsonian. You can build an excellent telescope by following the Kriege plans to the letter, but the internet provides many design alternatives. You might find incorporating some of them results in a scope better suited to your preferences.
I am impressed with some of the design approaches used by German ATMers. Particularly those of Achim Strnad and Stathis Kafalis. I am interested in their mirror boxes because a requirement for my mirror box is that it be no more than 9 inches tall so that it will fit into an external storage compartment on our OutdoorInn RV. Being able to remove the altitude bearings is critical for this. Also, using oversized bearings is important because it raises the center of gravity for the instrument above the top of the mirror box, making the scope easier to balance. I am not a fan of placing truss sockets on the outside of the mirror box. It seems awkward to me. Building a slightly oversized mirror box (with an outside dimension around 28-inches square for a 22-inch mirror) seems a reasonable way to ensure the truss is conical, while allowing additional space for installing the optic, cleaning, etc. Having the truss sockets inboard is stronger as well. The German mirror box design accommodates all these goals.
John VanderBrugge’s article “Remote Collimation for a Big Dob” in the November 2005 issue of Sky and Telescope magazine provides an excellent plan for enabling collimation adjustments from the eyepiece by utilizing electric drive motors to drive the collimation screws. It even provides Internet sources for the necessary parts. Collimation even on small dobs can be a pain because of all the back and forth. It’s generally a two person job on larger scopes. Especially considering the fast focal ratio of my mirror (an F4), which will require careful collimation, remote adjustment capability seems more valuable to me than tracking.
Local suppliers are also important for a project like this: not only because of the tools and materials they provide but also because of the specialized knowledge they are often willing to share with friendly customers. Lowes and Home Depot are good, as far as they go, but can’t compete with specialized suppliers for quality plywoods, metal stock, and uncommon parts. There are literally dozens of such companies in any large metropolitan area. In Kansas City, for example, Paxton Lumber carries an extensive stock of quality hardwood plywood. Schutte Lumber, which is closer to my house, also carries plywoods and an extensive stock of lumber not available from places like Home Depot. And they’re open on Saturdays. I’ve known about those companies for years, but discovered a great metal supplier in Kansas City only when I started this project. Metals by the Foot, which is only about 8 minutes from my house, offers all the metal stock (like stainless steel and 6061 alumninum) needed for telescope making and can accurately cut material to length. They also stock extensive hardware inventories in many different types of metal. You’ll build a much better scope if you’re willing to be adventurous and seek out speciality (often industrial) suppliers in your area.
Astronomy vendors are also an important resource for telescope making. I’ve gotten valuable advice and information from ProtoStar, AstroSystems, StarlightInstruments, AlpineAstro, and Kennedy-Optics to name only a few. A few more excellent companies I have had the pleasure to deal with while building my telescope include CatsEye Collimation: Jim Fly’s center spotting template is $17 well spent(!) and his passive collimation tools are the best available; Howie Glatter has a well-deserved reputation for extraordinary customer service, and his laser collimators are preferred by informed ATMers and telescope enthusiasts (for good reason); and Brian Musgrave at Telescope Solutions has designed the most effective Telrad Dew Heater on the market, AND is the only vendory I have found who offers custom cord lengths — large dobs need longer cords!
I’ve saved the best for last — the CloudyNights ATM forum. It’s home to wood workers, metal workers, and all kinds of experts, many of whom have years and years of telescope making experience. It is a friendly, extremely knowledgeable group that shares information with others for fun. How can you beat that?