I’ve owned and observed with a number of small to medium-sized telescopes, my largest being an 11-inch Celestron SCT. I like small scopes—they’re easy to handle and show a surprising amount for their size. For that matter, I like observing with hand held binoculars (even easier to handle and more surprising in their capability). But there have been occasions when I wanted to see more detail, or couldn’t find a faint object, or could barely see it. I’ve often looked through larger scopes owned by other Astronomical Society of Kansas City members. Perhaps the most memorable view I had was through a 20-inch StarMaster during an ASKC camp out at Schwartz Prairie. It was a view of the Cat’s Eye nebulae in Draco. I could see intricate and stunning detail that wasn’t observable in my smaller scope. It has been a few years since I had that view, but ever since then I have told myself one day I would own a large Dobsonian telescope.
Last October I decided it was time to get started on the project and took that important first step. (No, not ordering my primary mirror.) I casually mentioned the idea to my wife, also known as the Miles family CFO (Chief Financial Officer).
When I had provided a brief outline of the project, Elly took me in her arms, smiled warmly, and said “Dear, what a wonderful idea. You have my full support. Are you certain a 22-inch mirror is large enough? Perhaps you would rather have a 28-inch mirror? After all, it’s only money.” Well, maybe her response was a little more like “You want to WHAT!” Elly is a trouper, though, and really does support my interests, despite occasional sharp remarks about her “Man of 1,000 Hobbies.” After she had a week (or three) to mull the concept over, she gave her consent and my Large Dob project became a reality.
My next step was to decide on a vendor for my mirror. I visited web sites of a few companies that build large Newtonian mirrors for amateur astronomers. These tend to be operated by dedicated individuals who are in the business because they love astronomy. I also posted a question about mirror companies on the CloudyNights ATM (Amateur Telescope Making) forum. CloudyNights is a vital astronomy resource for all aspects of the hobby, and the ATM forum has proven to be my single most valuable source of information about the practical details of large dob construction. Several CN members mentioned Steve Kennedy, operator of Kennedy-Optics.
Steve specializes in large Newtonain mirrors with very short focal ratios. His slower mirrors are F4.0, and his preferred optic is a 28-inch F3.66 mirror. A lot of observers have been taking notice of his company. And ordering his mirrors, which have a reputation for outstanding quality. I sent Steve an email, and a few days later he called me. We spent an hour on the phone. Steve is passionately committed to mirror-making, extremely knowledgeable on the subject, and very generous in sharing information. He lives in Yucca Valley, California, a desert region with pristine viewing conditions that enable him to star test mirrors during the figuring process. He uses a specialized star-testing mount.
After one call with Steve, my choice of optical company was made. It took a few more calls to establish the mirror size and f-ratio. I opted for a 22-inch, F 4.0 (one of Steve’s slow mirrors!) I sent my deposit on November 29th. Several ATMers warned me that mirror makers can take a long time to deliver: many months and even, occasionally a year or more. (No one said this about Steve, I should add.) Steve’s plan was to order my blank, along with several other 22-inch blanks, from Newport optical and pick them up in early December. The mirror was to be finished by March.
I guess ATMers prefer really thin blanks. Steve got two 1.5-inch blanks and one 2-inch blank. He called me to discuss which I would prefer. I think he was a little worried because he already had two customers who wanted thinner blanks. I told him that was fine with me: I wanted the 2-inch blank anyway. I think pushing the design edge with the thinnest, lightest option possible is a risky approach to telescope making. I respect people who do it — many advances in Dobsonian telescope design have resulted from what they have learned. For myself, though, I like a more conservative approach with an emphasis on reliability and optical performance. It wasn’t long ago that 2-inches was considered the practical minimum for a large mirror!
Anyway, I was stunned and delighted in early January when Steve called to say he had finished my mirror. It was less than six weeks after I placed my order. Need I add that I think Steve is the greatest? If you’re looking for a large Newtonian mirror for your next telescope project, you owe it to yourself to investigate Kennedy-Optics.