12" f/4.9 telescoping truss-tube Dobsonian

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This Sky-Watcher Dobsonian has:

• fully multicoated 12” f/4.9 Newtonian reflector optics
• unique telescoping truss-tube design for compact transportability
• smooth Teflon bearings for altitude, with tension control 
• aluminum plate with needle bearings for azimuth 
• 2" Crayford focuser with 1.25" eyepiece adapter
• 10mm (150x) and 25mm (60x) 1.25” Plössl eyepieces
• 8 x 50mm right angle finderscope

    With the 12” Sky-Watcher telescoping truss-tube Dobsonian, you don’t have to worry about lifting the scope’s diagonal mirror cage and trying to bolt it to swaying truss tubes in the dark as you do with other truss-tube Dobs. Sky-Watcher's revolutionary telescoping truss-tube system attaches the top of the truss tubes permanently to the diagonal mirror cage, with the bottom of the tubes sliding into three die-cast housings on the scope’s primary mirror tub. 

    This unique system allows the optical tube's diagonal mirror cage and three attached truss tubes to slide down onto the primary mirror tub and be locked in place to form one surprisingly compact assembly. By undoing the no-tool handles in the sides of the altazimuth base that hold the optical tube in the base, the cage and tub assembly can be lifted out of the scope’s altazimuth rocker base as a single unit for easy and secure transport.

    Preparing the Sky-Watcher Dob for use involves simply unlocking the diagonal mirror cage and raising the cage until spring-loaded catches on the truss tubes snap into place in the primary mirror tub. This holds the cage in its fully-raised position while you tighten the no-tool locks at the base of the truss tubes to lock the diagonal mirror cage securely in position for observing.

    For binoviewing without unwanted extra magnification, a second set of indents on the truss tubes allows the diagonal mirror cage to be lowered to a preset locking position on the truss poles. This lets you to use a binoviewer without needing a corrector or Barlow lens in the binoviewer to reach focus.

    With a heaviest single component weight of only 46.2 pounds, the 12” Sky-Watcher is a telescope that most reasonably-fit individuals should be able to set up and transport with little or no problems. The complete 12” Sky-Watcher optical tube assembly – secondary mirror cage, truss tubes, and primary mirror tub – weighs only 46.2 pounds (21 kg). The altazimuth rocker box base it sits in weighs only 40.7 pounds (18.5 kg). Total weight is only 86.9 pounds, light for a full-sized 12” telescope.

    The Sky-Watcher easily collapses in minutes into two reasonably small and light components that fit into most car trunks or into the back seat of even a compact car. Competitive truss-tube Dobs break down into four or more components – a secondary mirror cage, primary mirror tub, altazimuth rocker box base, and truss tubes (as many as six to be carried separately or packed into an optional carrying bag). It’s easy to see how the two-part Sky-Watcher has a definite convenience advantage over the four or more parts of a conventional truss-tube Dob. And, unlike bulky competitive solid-tube Sonotube or metal tube Dobs with an unwieldy 58” or 60” long optical tube, you don’t need a big car to transport this 12” Sky-Watcher.

    Assembly and disassembly take only 10 minutes or so, with no tools needed. After you set up, particularly after traveling over bumpy roads to a dark sky site, take a few moments to check the collimation of the optics to assure peak performance and you are ready for an evening of fascinating viewing at your favorite dark sky location. If observing from your back yard, you can leave scope assembled and simply roll it outside using a hand truck or a JMI Wheeley Bar. 

    The 14” Sky-Watcher telescoping truss-tube Dobsonian is designed for visual observing only – to show you as much of the night skies as possible, and do it as conveniently and inexpensively as possible. Photography is not possible with a Dob.

    Because of its reasonable component size, sensible individual component weights, and limited number of components to put together (after all, there are only two!), one fit individual can normally transport and set up the 12” Sky-Watcher telescoping truss-tube Dob. Its innovative and unique telescoping design gives Sky-Watcher users a cost-effective 12” telescope with unsurpassed compactness and transportability.

This Sky-Watcher Dob’s Optical Tube Assembly . . .

Newtonian reflector optics: 12” diameter parabolic primary mirror, with 2.75” m.a. diagonal mirror. Both are guaranteed to be diffraction-limited. The diagonal mirror cage and primary mirror tub are made of rolled aluminum, anodized and finished externally with a subtle and attractive star-field pattern. Painted die-cast and machined rims hold the aluminum truss tubes and optical components in precise alignment to minimize the need for frequent collimation.

Primary mirror: Grade A annealed optical glass, 12” diameter, 1500mm focal length, nominally f/5 (actually f/4.9) parabolic in a fully adjustable metal cell provides sharp and bright high contrast images of nebulas, galaxies, and star clusters. Lunar and planetary images are also sharp and crisp, but a neutral density (Moon) filter would certainly be called for to cut down on the incredible solar system brightness provided by this 12” mirror – almost 1900 times that of your eye. The center-spotted mirror is ground with computer-controlled accuracy, multicoated with aluminum and titanium dioxide for high reflectivity, and then overcoated with quartz for long life.

Diagonal mirror: Grade A annealed optical glass 2.6” m.a. diagonal mirror, mounted in a fully adjustable diagonal holder on a low-diffraction four-vane thin spring steel spider. The diagonal mirror is polished flat to diffraction-limited accuracy. As with the primary mirror, the diagonal is multicoated with aluminum and titanium dioxide for high reflectivity and overcoated with quartz for long life.

Finderscope: 8 x 50mm right-angle erect image achromatic crosshair design. The images in the finder are erect and right-reading, with star patterns looking just as you see them on star charts or with your bare eye. It is mounted near the focuser, with the finder eyepiece vertically aligned in the same direction as the telescope eyepiece. This eliminates the constant head twisting involved when switching between the horizontal orientation of a conventional Dob’s straight-through or red-dot finder and the vertical orientation of its focuser and eyepiece.

Focuser: Machined aluminum 2” Crayford focuser with a 1.25” eyepiece adapter.

Eyepieces: 10mm and 25mm 1.25” four-element Plössl eyepieces with a 52° apparent field. The 25mm provides a magnification of 60x with an actual field of view 0.86° across. That’s almost one and three-quarters as wide as the full Moon. The 25mm gives rich and expansive deep space views of star clouds, galaxies, and nebulas alike. The 10mm Plössl provides a stout 150x magnification with a 0.35° field of view, enough magnification to provide sharp close-up views of the Moon, planets, globular star clusters, multiple star systems, and more.

Optical Tube Dimensions: The telescoping 12" optical tube measures 15.75" (400mm) in diameter, 55" (1397mm) long when extended, but a much more compact 36" (914mm) in length when retracted. The eyepiece is approximately 55.5" above ground level when the optical tube is pointed at the zenith.

This Sky-Watcher Dob’s Base Assembly . . .

  • Rocker box altazimuth base: The altazimuth rocker box that the mirror tub rides in is crafted of strong, lightweight, and water-resistant laminated particle board, as is the water-resistant ground board that the rocker box rides on. The base is shipped disassembled, but can be put together in about a half an hour using only a screwdriver and the supplied hardware. Teflon bearings in altitude with a tension clutch provide smooth and effortless vertical motion of the optical tube and let you adjust for varying eyepiece weights. For smooth motion in azimuth, the Sky-Watcher 12" Dob optical tube rides on an aluminum plate with needle bearings.

  • Navigation knob: A navigation knob conveniently mounted below the focuser makes it easy to control the scope’ motion in any direction. The optical tube starts moving at a gentle touch – smoothly and with no fuss. Center on an object and the scope settles down immediately, with no shudder or vibration to mar your viewing experience.

  • Carry handles/altitude tension control/eyepiece tray: The handles in the sides of the rocker box incorporate a tension control in altitude that lets you compensate for eyepieces of markedly differing weights. An eyepiece tray capable of holding one 2” and three 1.25” eyepieces attaches to the front of the rocker box above the supplied centrally-mounted carrying handle.
  • Altazimuth base dimensions: 25" in diameter by 29" high.

What can you see through the 12” Sky-Watcher telescoping truss-tube Dob?

    Everything in deep space appears brighter, and wider in extension, with the 12” Sky-Watcher. You now have the tremendous light gathering power to see faint and distant nebulas and galaxies that you’ve always wanted – almost 1900 times that of your unaided eye. Many of the objects that are a challenge to even see in smaller aperture telescopes now show their essential structure. Objects just within the threshold of visibility with a 10” aperture scope appear more prominent with the 12” and may be worth observing for extended periods. Comet hunters will delight in the fainter magnitudes that are possible to see in the 12” Sky-Watcher. Here at last is a telescope with the ability to visually tackle elusive deep-space gems like the Horsehead Nebula in Orion. In Perseus, the very faint 11th magnitude nebula M76 will be visible from a dark sky site, as will very faint planetary nebula M9 in Ursa Major. M61, the spiral galaxy in Virgo, reveals its spiral arms as you’ve always hoped to see them. The list goes on and on, and you will delight in planning your own nightly journeys of exploration.

    Compared to an 8” or 10” scope, the increased resolution and greater light-gathering power of this Sky-Watcher’s 12” aperture is beyond just being impressive. It lets its lucky owner resolve many, many objects that smaller telescopes simply don't have the horsepower to show satisfactorily because they can't pull in enough light. Compared to an 8” scope, the 12” Sky-Watcher has 50% greater resolution of small details and two and a quarter times the light-gathering to reveal fainter objects. Even compared to a 10” scope, the 12” Sky-Watcher has 20% higher resolution and 44% greater light-gathering. The 12” Sky-Watcher's compact, telescoping optical tube design makes this super aperture 12” Dob a practical step up for the serious observer.

    As with any large aperture telescope, the performance of the 12” Sky-Watcher on faint objects will be markedly improved by a dark sky observing site. Light-polluted city and suburban sites are definitely not recommended as the primary observing site for a 12” scope. Such sites require a nebula (light pollution) filter to take even limited advantage of its immense light-gathering.

    While it is in deep space observing of galaxies and nebulas from a dark sky observing site that the 12” Sky-Watcher telescoping truss-tube Dob excels, significant planetary and lunar observing is also within its capability. All you need is a neutral density eyepiece filter to cut down the immense brightness of solar system objects seen through this “light bucket."

    Taking advantage of the weight-saving sophistication of its telescoping truss-tube design, the 86.9 pound Sky-Watcher 12” Dobsonian makes it practical for almost any individual on his or her own to explore the heavens with a truly big scope, whether from a back yard or a distant dark sky observing site. This Sky-Watcher 12” telescoping truss-tube Dobsonian reflector will keep you happily observing the faint and distant outer reaches of the Universe for many years to come.

Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

0.38 arc seconds
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
The weight of this product.
86.9 lbs.
Heaviest Single Component:
The weight of the heaviest component in this package.
46.2 lbs.
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Very Good
Planetary Observation:
Binary and Star Cluster Observation:
Galaxy and Nebula Observation:
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Planetary Photography:
Star Cluster / Nebula / Galaxy Photography:
View Finder:
8x50mm r. a.
1 year
Reviews from Cloudy Nights (www.cloudynights.com)
These reviews have been written by astronomers just like you and posted on the Cloudy Nights astronomy forums . . .
Sky Watcher 12" Dob Review.

User Ratings/Reviews from our Customers (www.astronomics.com)
Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(4.50)   # of Ratings: 2   (Only registered customers can rate)

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1. Jeff on 4/4/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I really love this telescope, although it is heavy to haul in and out of the house everyday. Being collapsible helps considerably in doing this. It is a very sturdy built scope and the views of Saturn, Jupiter, and Orion have been fantastic. I think the 25mm and 10mm SuperPlossls that come with it are decent eyepieces. It took me around an hour to assemble it.

The only negative I have found, thus the reason for the four stars, is that collimation does not seem to hold for the primary mirror. I have had to adjust it everytime I take it out to the backyard. I use a laser collimator and line up the light to the center of the target each time, and every time I go out it needs aligned again. I believe it has to do with the tightnening screws on the primary mirror. It is a little work to tighten them and keep the mirror in the center. I don't know if moving the telescope back to it's stand makes it go off a little. Collimation is quick an easy so I do it every time I go out, but wished I only had to adjust the secondary mirror and not the primary also. Maybe this will change a little with time.

Over all I love this thing and would recommend it to anyone who wants to reach out there and see some good views of some distant objects. This is not for the people with back problems, because it is heavy. I am only 5'8" and have no problem with it, but it's big!
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2. Corey on 3/11/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
A great scope at a great price. The telescoping action makes moving this giant so much easier than bear hugging a sonotube or carrying multiple pieces of a truss tube. The optics are wonderful and everything is very sturdily built.
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We haven't recommended any accessories for this product quite yet... check back soon or call one of our experts (1-405-364-0858).
  • Telescoping no-tool assembly truss tube design
  • Rolled aluminum/die-cast secondary mirror cage and primary mirror tub
  • Navigation knob
  • Laminated altazimuth mount with Teflon bearing surfaces and altitude tension control
  • 4-vane spring steel diagonal mirror support with adjustable mirror holder
  • Adjustable primary mirror flotation system
  • Diffraction-limited Grade A optical glass mirrors
  • Protective primary mirror cover
  • 2” Crayford-style machined aluminum focuser with 1.25” eyepiece adapter
  • 25mm (60x) and 10mm (150x) 1.25" Plössl eyepieces
  • 8x50mm right angle finderscope.
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Sky-Watcher - 12" F/4.9 telescoping truss-tube Dobsonian

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Sky-Watcher - 12" F/4.9 telescoping truss-tube DobsonianAnother view of the Sky-Watcher 12" truss-tube Dob.Closer view of the 12" Sky-Watcher Dob showing the focuser, finder, and one of the truss-tube locks.
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Our Product #: SW12D
Manufacturer Product #: S11740
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This 12” Sky-Watcher Dobsonian reflector is a user-friendly telescope for the serious amateur who wants serious deep-sky light-gathering. It combines the proven “more light-gathering bang for your buck” economy of the Dobsonian telescope design with the exceptional convenience and portability of Sky-Watcher's unique telescoping truss-tube system.

. . . our 39th year