AT10D 10" F/4.9 Dobsonian reflector

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This 10” Astro-Tech Dobsonian reflector has:

• Diffraction-limited parabolic Newtonian optics
• dual-speed 2” Crayford focuser with 1.25” adapter
• innovative ball-bearing altitude motion with clutch
• smooth roller-bearing azimuth motion
• tube balance system
• 8 x 50mm fully-multicoated achromatic finderscope
• 2” 30mm SuperView 68° field eyepiece and 1.25” 9mm Plössl eyepiece
• battery-operated primary mirror cooling fan
• eyepiece tray
• free shipping

    Like all Dobsonian reflectors, this 10” f/4.9 Astro-Tech AT10D Dob “light bucket” gives you more light-gathering for your dollar than any other telescope type – only about $10.21 per square inch of light gathering. It shows you faint deep space objects that are simply invisible in smaller scopes. With a visual limiting magnitude of 14.5, this 10” 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.

    The 10” Astro-Tech Dobsonian is easy to get to your favorite observing site, too, whether that be your own back yard or a dark sky site miles out of town. The Astro-Tech AT10D breaks down into two components – a 48” long x 12” diameter rolled steel optical tube and a 22” diameter x 25” tall wooden rocker box altazimuth base. It weighs only 60 pounds fully assembled. And assembling the AT10D takes just a moment, with no tools needed. Simply lift the optical tube, rest its circular altitude bearings in the semi-circular cutouts in the sides of the rocker box, put in an eyepiece, and you’re ready to observe.

    The performance of the BK7-equivalent optical glass mirrors of the 10” 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, generally limited only by seeing conditions, although a neutral density filter is typically required to allow glare-free observing. The mirrors are overcoated with quartz for long life.

    The 10” Astro-Tech Dobsonian is a “light Bucket” designed for visual observing only – to show you as much of the faint fuzzies in the night skies as possible, and do it at an affordable price. Photography is not possible with a Dob.

    Under dark skies, the 10” aperture of the AT10D turns the Orion Nebula into a glowing and subtle complex of filaments, and color starts to become visible. The spiral structure of the Whirlpool Galaxy becomes apparent, as do dark dust lanes across the nucleus of the Andromeda Galaxy (although the full 3° width of the galaxy itself is far too large to fit into the field of view of any eyepiece generally usable with the scope). Globular clusters are frequently resolved to the very core. Messier, NGC, and IC objects show detail and structure never visible in smaller telescopes. As with any large aperture telescope, the performance of the 10” Astro-Tech 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 a 10” 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 10” Astro-Tech AT10D 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.”

    Simply-made, but with precision Newtonian optics, this Astro-Tech 10” Dobsonian reflector will reward you with bright deep space and solar system views and years of trouble-free observing enjoyment.

This Telescope’s Optical System . . .

  • Type: Newtonian reflector with parabolic primary mirror.

  • Primary mirror: 10” (254mm) diameter, 1250mm focal length, f/4.92 focal ratio. The mirror is made of B270 “water white" optical crown glass that is free of internal stress and striae. B270 glass is equivalent to BK7 in performance and optical quality. The thermal stability of B270 glass is generally better than the soda lime float glass used for the mirrors of most reflectors in this reasonable price range. The mirror is ground and polished under computer control for guaranteed diffraction limited performance, coated with 91% reflectivity aluminum, and overcoated with a protective layer of silicon dioxide (quartz) for long life.

  • Primary mirror cell: Fully adjustable 3-point flotation system metal cell holds the primary mirror. 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 push-pull 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 a battery pack that uses eight user-supplied AA batteries and plugs into a jack on the mirror cell frame.

  • Diagonal mirror: 63mm m.a. B270 “water white" optical crown glass, coated with 91% reflectivity aluminum and overcoated with a protective layer of silicon dioxide (quartz) for long life.

  • 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 extension tube for eyepiece use is standard equipment. The extension tube, and 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 (42x) 68° field SuperView eyepiece with a wide 1.6° actual field of view that’s well over three times the diameter of the full Moon. The second is a fully multicoated high power 1.25” 9mm (139x) 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 straight through fully-multicoated dark crosshair achromatic design. The finder has a long and comfortable 13mm eye relief. It 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 finderscope mounts in a quick release bracket that slips into a pre-installed metal mounting shoe beside the focuser. The bracket is held in place in the mounting shoe by a single large hand-tighten chrome-plated knob that maintains the finder’s collimation, even if the finder is removed between observing sessions.. 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.

This Telescope’s Mount . . .

  • Type: Standard rocker box Dobsonian mount.

  • 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 10” 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 invariably get trapped between the exposed circular trunnions and the Teflon pads of conventional Dobsonians and scores the surfaces. 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 focuser from rising or sinking when changing between eyepieces of considerably different weights, for example when switching between 1.25” and 2” eyepieces.

  • Tube balance system: The altitude bearings of the AT10D are bolted to slotted plates attached to the optical tube. This allows the optical tube to be moved fore and aft in the slots to balance the 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 resulting 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 with your heaviest eyepiece installed. 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 between eyepieces of different weights.

  • Altazimuth base (rocker box): The altazimuth base that the optical tube 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 AT10D 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. A carrying handle is provided to make carrying the rocker box easier.
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.

0.46 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.
60 lbs.
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.  
Planetary Observation:
Very Good
Binary and Star Cluster Observation:
Very Good
Galaxy and Nebula Observation:
Very Good
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:
1 year
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1. Jev on 5/15/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
My first Dobsonian. My previous telescope was a 4" refactor. Needless to say, this thing can really pull in the light. I bought it because I wanted to see some galaxies. While still a total noob. I've managed to spot 1/2 a dozen galaxies from my backyard which is on the border of red/orange on the light pollution map.
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2. Dan on 5/2/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
The AT10D is untouchable at this price (including free shipping!). The included eyepieces, mirror fan and dual-speed focuser makes it a cut above comparable scopes from the outset. The optics are excellent and the unique altitude adjustment system is fantastic. There are, however, a few issues that have cropped up. The biggest issue is the azimuth motion. There is a bolt in the bottom of the rocker box that you can tighten or loosen to adjust the stiffness of motion. The problem is that the bolt comes loose after moving the scope around just a few times, making it way too susceptible to even the smallest nudge. I put a base and some casters on the bottom of mine and at the same time compressed the ball-bearing ring plates a bit to overcome this problem. Additionally, the 1.25” adapter that came with the scope was defective (eyepieces would become stuck). Astronomics sent out a replacement right away and I have had no issues with that replacement. I would recommend this scope to anyone.
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Visual Accessories
Barlow Lenses (1)
2X apochromatic ED Barlow for 2" eyepieces, with 1.25" adapter
by Astro-Tech
Collimating Tools (1)
Newtonian reflector collimating tool
by Celestron
Eyepieces (2)
20mm 1.25" Value Line Plössl
by Astro-Tech
6mm 1.25" Value Line Plössl
by Astro-Tech
Filters (1)
1.25" #ND9 13% Transmission neutral density grey Moon filter
by Astro-Tech
  • 10” f/4.9 diffraction limited BK7-equivalent optics
  • 3-point primary mirror floatation system
  • Dual-speed 2” Crayford focuser with 1.25” adapter
  • Ball-bearing altitude motion with clutch
  • Roller-bearing azimuth motion
  • Tube balance system
  • Battery-operated cooling fan
  • 8 x 50mm finderscope
  • 2” 30mm SuperView eyepiece
  • 1.25” 9mm Plössl
  • Eyepiece tray
Astro Tech 8" & 10" dobsonian manual 1001kb(s)
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Astro-Tech - AT10D 10" F/4.9 Dobsonian reflector

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Astro-Tech - AT10D 10" F/4.9 Dobsonian reflectorClose-up of the AT10D dual-speed Crayford focuser, 2" eyepiece, and finder bracket.Close-up of the altitude bearing assembly and tension knob of the Astro-Tech AT10D Dobsonian.
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Our Product #: AT10D
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Clear skies,

This economical 10” Astro-Tech AT10D Dobsonian reflector “light bucket” reveals lots of detail in the faint fuzzies outside the solar system for not a lot of money. It’s easy to transport, easy to assemble, easy to own, and easy to use . . .

. . . our 34th year