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Sky-Watcher 150mm f/8 Dobsonian

This is a smaller version of the Sky-Watcher 200mm f/6 Dobsonian which I reviewed earlier. It shares most of the same design and components, with the exception of having a new 2" Crayford focuser replacing the 2" rack and pinion focuser. The 200mm now comes with this focuser as standard equipment, too.

The included assembly instructions are more complete than the ones that came with the 200mm, but they still don’t describe how to assemble the new focuser. The scope went together easily once I replaced the first box of mount components because the base of the rocker box was missing.

The only mechanical problem I encountered was that the tube was front heavy, the opposite of the problem with the 200mm. It was only when I was repacking the scope that I discovered a metal plate in the box which serves as a counterweight. This fixes the problem, but severely restricts the air flow to the back of the mirror. My preference would be to leave this plate off and find some other way of adding a bit of weight to the mirror end of the tube.

The new Crayford focuser is a joy to use, being very smooth in operation and capable of fine adjustments. Except for my 22mm Nagler, all eyepieces, 1.25" and 2", reached focus without any problems. The original focuser was good, but the new one is even better.

Like every Sky-Watcher scope I’ve tested, this one arrived perfectly collimated out-of-the-box, and has held its collimation over the period I’ve been testing it. This speaks highly of the mechanical integrity of the scope, and alleviates the beginner’s greatest anxiety about Newtonians. No doubt the scope will require collimation at some point, but if it can make it to Canada to from China without losing collimation, it should be pretty stable.

I tested the telescope under the stars on four different nights, exploring a wide range of objects. Well, actually, one night and three mornings, as I was unable to resist the lure of using this scope on my old favourites, Jupiter and Saturn, currently in the predawn sky. I also spent time looking at the Moon, Mars, and Venus, favourite double stars like Epsilon Lyrae (split easily at 120x) and Rigel, and deep sky showpieces like the Ring Nebula and the Orion Nebula. All were well shown, as one would expect in a good quality 150mm scope. The supplied eyepieces, 25mm and 10mm "Super" modified achromats with 50° fields, performed quite well, yielding magnifications of 48x and 120x. This scope showed that it can handle much higher powers easily; I found myself using a 6mm eyepiece (200x) on the Moon and planets most of the time. Fans of deep sky objects will probably want to add a 2" eyepiece to take in the wide field of view this scope is capable of.

As Terry Dickinson says in NightWatch, "There may not be a perfect telescope for the beginner, but the closest thing to it is the 6-inch Dobsonian-mounted Newtonian reflector." The Sky-Watcher 150mm is an excellent example of this breed, at a very attractive price. My wife and I usually donate a telescope to our favourite charity to auction off each year, and this year this scope is our choice. Highly recommended!

As you may have noticed, this scope sells for exactly the same price as the Sky-Watcher 130mm f/5 equatorial Newtonian, which I reviewed very positively. Both scopes are of excellent quality representing good value. Which to choose? It boils down to whether you want an equatorial mount enough to sacrifice a bit of aperture. For most people, the 150mm Dobsonian is probably the better choice, offering more aperture on a steadier mount. The 130mm equatorial might be a better choice if you plan to add a motor drive or like the wider vistas provided by its shorter 650mm focal length. The 150mm offers almost as wide a field of view, provided you go to a 2" eyepiece, which is a much more expensive proposition. Tough choice, but either way you will get a solid performer that will give you satisfaction for many years.

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