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I'd Still Buy The Dob

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Posted by Daniel Johnson on January 14, 2003 01:03:31 UTC

I've owned seven or eight scopes over the years. Aperture, well-made optics, and a solid mount come before other considerations, I think, unless one wishes to be a serious astrophotographer (in which case the cost of the scope will be less than the cost of the accessories you buy, and the scope alone will be three times the cost of a Dob of the same aperture).
I think the praises of refractors are overblown, except for premium refractors sold for photography (such as Takahashi, Borg, TeleVue, and so on. They are wonderful for what they do). The idea that a five-inch refractor will outperform a 10-inch Dob of similar price is just not true, as a recent Sky & Telescope article explained at length. I've done side-by-side comparisons of Newtonians/Dobs and good refractors for both planetary and deep-sky work. The Dob, having twice the aperture (or more) for the price, wins. This is only true, however, if you take constant care in keeping the Dob collimated. Their "sweet spot" can be small, and if your collimation is off you'll be disappointed. See the recent article in Sky & Telescope (one of the last 2 or 3 issues) on collimating with a Barlowed laser--it's brilliant and simple.
Yes, you have to push the Dob to track objects. At high powers (planetary work) this is a bother, but not terribly so. I have timed eclipses of Jupiter's moons on at least 50 occasions with a Dob. At lower powers, for deep sky work, pushing the Dob is just not a problem. It's easy.
Having said that, I'll admit my trusty old 12.5" Dob is gathering dust, but only because I now have a similar-aperture SCT. At similar apertures, computerized and motorized scopes win hands down, but the cost is far higher. For visual (as opposed to photographic) work, if you want to see as many objects as you can within a certain budget, the Dob is the winner. Period.

--Dan Johnson, owner of a Dob, an SCT, two Maksutov-Cassegrains, and a refractor.

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