Dobsonian reflectors

More Information  · Supplied Accessories  · Related Documents  · Images of Some Features Price $2,395.00 Highest Useful Magnification 360x Visual Limiting Magnitude 15.5 Focal Length 1800mm Focal Ratio f/4.5 Resolution 0.29 arc seconds Aperture 16" Net Weight 134 lbs. Heaviest Single Component 60 lbs. Warranty 1 year

• 1/12th wave BK-7 optics
• 18-point primary mirror floatation system
• innovative three-strut truss-tube design
• dual-speed 2" Crayford focuser with 1.25" adapter
• innovative ball-bearing altitude motion with clutch
• smooth roller-bearing azimuth motion
• tube balance system and cooling fan
• 8 x 50mm right angle erect-image right-reading finderscope
• 2" 30mm SuperView eyepiece and 1.25" 9mm Plössl eyepiece
• laser collimator, eyepiece tray, Moon filter
• free air shipping direct from the manufacturer

    Like all Dobsonian reflectors, this very complete 16" Astro-Tech truss-tube Dob gives you more light-gathering for your dollar than any other telescope type. Its very large 16" aperture gathers four times the light of an 8" scope (and almost 3400 times as much as the sharpest dark-adapted eye)! The result? It shows you very faint deep space objects that are simply invisible in smaller scopes. And color is often visible in the brighter nebulas. With a visual limiting magnitude of 15.5, this 16" Astro-Tech is ideal for observing faint nebulas, galaxies, and star clusters from a dark sky site – all the faint fuzzies outside the solar system that fascinate us.

    Despite its large aperture, the 16" Astro-Tech Dobsonian is easy to get to your favorite observing site, whether that be your own back yard or a dark sky site miles out of town. Unlike a bulky Sonotube or metal tube Dob, you don’t need a van or small truck to transport this big 16" scope to the dark sky sites it needs to perform at its best. The 16" Astro-Tech breaks down into a few compact components that fit into virtually any car trunk or into the back seat of just about any compact car. It weighs only 134 pounds fully assembled. Assemble the AT16D in just a few minutes, with no tools needed, and you’re ready for an evening of fascinating viewing at your favorite dark sky location.

    The first component is the 14 pound aluminum upper cage containing the diagonal mirror, 2" focuser, and 8 x 50mm right angle erect image finderscope. Second is the 60 pound aluminum mirror tub holding the primary mirror in its 18-point flotation cell. Three light-weight (6 pounds total) but very rigid single strut aluminum truss tubes connect the secondary cage to the mirror tub. They have die-cast brackets with curved notches that mate with projections on the cage and tub rims by means of large hand-tighten knobs, making assembly easy. Finally, there’s the 54 pound laminated particle board base (rocker box) in which the mirror tub sits.

    With 1/12th wave surface accuracy, the performance of the BK7 optical glass mirrors of the 16" Astro-Tech Dobsonian is guaranteed to be diffraction limited – for sharp high contrast images of nebulas, galaxies, and star clusters. Planetary images are also sharp and crisp, although a neutral density filter is certainly required to allow glare-free observing. The mirrors are overcoated with quartz for long life.

    Because of its compact individual component sizes and reasonably light component weights, the 16" Astro-Tech can easily be transported and assembled by one dedicated individual, although two people will generally make it easier to assemble aluminum upper cage to the truss tubes. Set-up time is only about 15-20 minutes.

    The 16" Astro-Tech Dobsonian is designed for visual observing only – to show you as much of the night skies in as much detail as possible. Under dark skies, color becomes visible to the eye in many nebulas. The Orion Nebula becomes a glowing blue-green mass of filaments, often tinged with red and yellow for the keen-eyed observer from a dark sky site. With a resolving power of 0.29 arc seconds, globular clusters can often be resolved to their cores in good seeing, with each cluster becoming a vivid ball of tiny individual stars instead of a hazy blur. Knottings and structure in the arms of the Whirlpool Galaxy become clear. Mighty globular clusters in the distant Andromeda Galaxy begin to reach the threshold of visibility for the exceptionally keen-eyed observer.

    As with any large aperture telescope, the performance of the 16" Astro-Tech Dobsonian on faint objects will be markedly improved by a dark sky observing site. Light-polluted city and suburban sites are not recommended as the primary observing site with any 16" scope. Such light polluted sites require a 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 16" Astro-Tech Dobsonian excels, significant planetary and lunar observing is also within its capability. Small details in the atmospheres of Jupiter and Saturn and on the surface of Mars reveal themselves at high powers given suitably good seeing. All you need is steady skies and a neutral density eyepiece filter to cut down the immense brightness of solar system objects seen through this immense “light bucket."

    The 218 pound shipping weight 16" Astro-Tech Dobsonian is shipped freight-free directly to you via air freight from the manufacturer in Taiwan. This avoids double shipping from the manufacturer to Astronomics and then from Astronomics to you, thereby avoiding much of the potential for damage during handling in transit. The heaviest carton weighs 148 pounds, so two people will probably be required to move it into the house after accepting delivery.

    Simply-made, but with precision optics, this Astro-Tech 16" Dobsonian reflector will reward you with thousands of bright deep space views and years of trouble-free observing enjoyment.

This Telescope’s Optical System . . .

• Type: Newtonian reflector with parabolic primary mirror.

• Primary mirror: 16" (406mm) diameter, 1800mm focal length, f/4.5 focal ratio. BK-7 optical glass, polished to 1/12th wave accuracy, aluminized and overcoated with a protective layer of silicon dioxide (quartz) for long life. 92% to 94% reflectivity. The mirror is center-spotted to aid in collimation. The mirror comes with a protective molded hard plastic cover that snaps into place to keep dust and debris off the mirror during transport and storage.

• Primary mirror cell: Fully adjustable 18-point flotation system metal cell holds the primary mirror. The 18-point floatation system supports the large mirror uniformly, so that it holds its parabolic figure precisely, regardless of the optical tube’s orientation. The open frame of the cell allows the mirror to cool down to ambient temperatures quickly, so you can start observing sooner. Large hand-tighten color-coded collimation and collimation lock knobs make it easy to collimate the primary mirror with no tools required.

• Primary mirror cooling fan: A lightweight 4.7" diameter low-vibration cooling fan is built into the mirror cell to assure faster cool-down times. The battery-operated fan is powered by an AA battery pack (batteries not supplied) that plugs into a jack on the mirror cell frame.

• Diagonal mirror: BK-7 optical glass, polished to 1/12th wave accuracy, aluminized and overcoated with a protective layer of silicon dioxide (quartz) for long life. 92% to 94% reflectivity.

• Diagonal mirror support: Fully adjustable diagonal holder mounted on a low-diffraction four-vane thin spring steel spider.

• Focuser: Dual-speed 2" Crayford type, with 1.25" eyepiece adapter. The machined aluminum focuser has dual coarse focusing knobs for smooth and precise image control with either hand. There is a separate 10:1 reduction ratio microfocus knob for ultra-fine focusing at high magnifications. The ribbed focus knobs are easy to operate, even while wearing gloves or mittens in cold weather. A 35mm eyepiece extension tube is standard equipment. Both the 2" eyepiece holder and the 1.25" adapter use non-marring soft brass compression rings to hold eyepieces in place, rather than simple thumbscrews that can scratch your eyepiece barrels.

• Two eyepieces: One is a fully multicoated 2" 30mm (60x) 68° field SuperView eyepiece with a wide 1.13° actual field of view that’s two and a quarter times the diameter of the full Moon. The second is a fully multicoated high power 1.25" 9mm (200x) 52° field Plössl.

• Eyepiece tray: A standard equipment eyepiece tray attaches to the side of the scope’s altazimuth base. It has cutouts to hold one 2" eyepiece and three 1.25" eyepieces.

• Finderscope: 8 x 50mm right angle achromatic design with a built-in image-erecting Amici prism. Images in the finderscope are upright and correctly oriented left to right. The star patterns seen in the finderscope are oriented the same way as they appear on star charts and to your unaided eye to make star-hopping easier. Focuses by loosening the trim ring behind the objective lens cell, screwing the lens cell in or out to focus, and tightening the trim ring to lock in the correct focus.

• Finderscope bracket: The 8 x 50mm right angle finderscope mounts in a quick release bracket that slips into a pre-installed metal mounting shoe on the secondary cage to maintain its collimation, even if the finder is removed between observing sessions. The bracket is held in place in the mounting shoe by a single large hand-tighten chrome-plated knob. The bracket has two hand-adjust collimation screws that work in conjunction with a third spring-loaded post in the bracket. This makes collimation faster than the traditional three- or six-screw collimation methods used with conventional finder brackets..

• Moon filter: A 1.25" glare-reducing Moon filter is standard, given the immense light-gathering capacity of the 16" optics that would otherwise wash out lunar detail.

• Laser collimator: A supplied 1.25" battery-operated laser collimator for Newtonian reflectors is standard equipment. It combines with the center-spotted primary mirror to make quick work of collimating the fast focal ratio AT16D in the field using the large no-tool hand-adjust collimation knobs.

This Telescope’s Mount . . .

• Modified truss tube Dobsonian mount: Instead of the usual six-tube truss design, the Astro-Tech 16" Dobsonian uses a less-complex three-strut design. The altazimuth base and upper (diagonal mirror) cage are joined by three modified trapezoidal cross-section aluminum struts, rather than the six tubes used on most conventional Dobs. The modified trapezoidal struts actually have eight distinct facets, providing exceptional torsional rigidity (resistance to twisting).
  The aluminum struts have die-cast brackets at each end, each with two semi-circular notches. Each notch has a captured bolt in its center, with a large hand-tighten knob. These semi-circular bracket notches mate with threaded semi-circular projections on the cage and tub rims, making alignment of the attachment bolt and its corresponding cage or tub rim hole easy and precise. When the three struts are attached to the mirror tub, their upper brackets provide a secure rest for the lightweight upper (diagonal mirror) cage, making it possible for one person to assemble the upper cage to the struts (although two people add an extra measure of safety during assembly).

• Primary mirror tub: The primary mirror and its cell ride in an aluminum tub with die-cast rims for strength and rigidity. The mirror tub has two combined altitude bearing/clutch/balance system assemblies that slip into cutouts in the sides of the altazimuth base (rocker box).

• Altitude ball bearings: Instead of the usual large circular trunnion bearings riding on a few Teflon pads in the semi-circular cutouts in the altazimuth base, the 16" Astro-Tech Dob uses innovative sealed metal ball-bearing systems to provide smooth vertical motion of the optical tube. The aluminum bearing housings fit snugly into cutouts in the sides of the altazimuth base. Because the bearings are sealed systems, the elements cannot affect the smoothness of the Astro-Tech’s vertical motion, as it can when dust and grit get trapped between the exposed trunnions and Teflon pads of conventional Dobsonians and scores the surfaces, as it invariably does. The vertical motion of the Astro-Tech tube is consistently ball-bearing smooth. And the sealed ball-bears will not have to be replaced regularly, as is the case with the Teflon pads of many Dobsonians as windborne grit degrades the Teflon/trunnion interface.

• Altitude clutch: Large ribbed clutch knobs are built into the two altitude bearings. A gentle twist on either knob adjusts the amount of friction within the altitude ball-bearing systems. This allows you to keep the diagonal mirror cage from rising or sinking when changing between eyepieces of considerably different weights, as for instance when switching between 1.25" and 2" eyepieces.

• Tube balance system: The altitude bearings of the AT16D are bolted to slotted plates attached to the mirror tub. This allows the optical tube to be moved fore and aft in the slots to balance the assembled optical tube. The altitude bearings have been positioned at the factory to balance a wide range of eyepiece weights with the occasional help of the altitude clutch knobs. However, if you have mostly heavy eyepieces in your observing kit, you may want to adjust the tube balance to compensate for the tube’s nose-heavy balance.
  By tilting the optical tube down until it is parallel with the ground, and loosening the altitude clutch knobs, you can observe whether the eyepiece end of the tube rises or falls when you let the tube go. You can then loosen the balance lock screws on the altitude bearings and slide the altitude bearings back or forth in the slotted plates as needed to balance the optical tube properly. An engraved scale on each plate makes it easy to move both altitude bearings the same amount. Tighten the balance lock screws and your tube is balanced for the majority of your eyepieces. Balancing the tube needs only be done once if you discover that your optical tube is consistently nose- or tail-heavy. The altitude clutch knobs will take care of most occasional minor imbalance situations when changing eyepieces.

• Altazimuth base (rocker box): The altazimuth base that the mirror tub rides in is crafted of strong, lightweight, and water-resistant laminated particle board. The base is shipped disassembled, but can be put together in about a half an hour using only a Philips-head screwdriver and the supplied hardware and hex-head wrench. The AT16D moves in azimuth on dozens of steel roller bearings riding between two metal plates. Push the scope lightly in any direction and it starts moving at the touch of a finger – smoothly and with no fuss. Stop pushing and it settles down immediately, with no shudder or vibration to mar your viewing experience. Carrying handles are provided to make carrying the 54 pound rocker box easier.

The feature illustrations of the AT16D shown below are of the white-finish prototype to make it easier for you to see details, but the production models are finished in black as shown in the images at the top of this page.

The Astro-Tech AT16D is a big scope – big in aperture, big in performance, big in value. Easy to transport, easy to assemble, easy to own, and easy to use, it can be your introduction to a universe simply invisible in a smaller scope. And this Astro-Tech can be yours only a few short days after you order it.