| Many observers believe that the 8" aperture of the Orion SkyQuest XT8 IntelliScope provides the perfect balance of light gathering, resolution, and economy for the amateur astronomer. Big enough to keep you busy observing for the rest of your life, yet not so big that it becomes inconvenient to set up on the spur of the moment for a half hour or so of observing. Its performance and convenience makes it the perfect big scope for the newcomer to astronomy. The XT8 IntelliScope is a 8" Dobsonian reflector with an IntelliScope object locating computer that makes it easy for you to quickly find more than 14,000 fascinating celestial wonders. With the IntelliScope, you spend more of your time looking at the intriguing faint fuzzies in the sky, and less time looking for them. The XT8’s great light-gathering capacity (over 800 times greater than the human eye) makes it ideal for capturing faint deep space wonders. Binary stars, open and globular star clusters, faint nebulas and galaxies – all are revealed in exceptional and subtle detail, even through mildly light-polluted suburban skies. At the same time, excellent planetary and lunar images are yours for the looking, although a neutral density filter is generally needed to cut down the brightness of these solar system objects. The scope is human powered. The user moves the scope manually – which is faster, quieter, and eats fewer batteries than motorized systems. With only two major components to assemble (tube and base), the scope takes only a few minutes to set up and is easily manageable by any fit individual. It can be used in your back yard or at a distant dark sky site (the preferred observing location if you want to get the utmost out of its faint object observing capabilities). Its good optical quality and very reasonable price for such a technically advanced and convenient telescope make it an excellent buy for the beginner or more advanced astronomer alike.
This Telescope’s Optical System . . . Newtonian reflector optical tube: 8" (203mm) aperture classical Newtonian optics, 1200mm focal length, f/5.9 focal ratio. The durable 46.5" long x 9.25" diameter rolled steel optical tube weighs only 20.3 lbs, making it easy to transport and assemble in the field. A “navigation knob" at the front of the tube provides a convenient grip that makes it easy for you to move the scope around the sky as directed by the IntelliScope object locating computer. Coated optics: The 8" parabolic primary mirror is center-marked for easier collimation. After polishing, it is coated with highly reflective aluminum and overcoated with a protective layer of quartz for long life. Primary mirror cell: Die cast aluminum cell with open back design for faster cool down times. A battery-operated cooling accelerator fan that mounts on the rear cell is also available as an option. Push-pull locking collimation bolt pairs help hold the correct collimation longer. Diagonal mirror: The 1.85" m.a. diagonal is coated with aluminum and overcoated with a protective layer of quartz for long life. It is mounted in a fully-collimatable mirror holder on a thin four-vane spider for minimum diffraction. Finderscope: 9 x 50mm right-angle correct image achromatic crosshair design, with a good 5° field of view, in a quick-release collimatable holder. The correct image prism in the finder shows you the sky the way it appears to your eye and on star charts. There’s no confusing mirror image view as you find with a conventional right-angle finder. 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. Focuser: 2" aluminum Crayford type, with removable 1.25" accessory adapter. The Crayford-style focuser has silky-smooth backlash-free motion that eliminates image shift, making it easier to achieve the sharpest possible focus. Two eyepieces: Two multicoated 1.25" Sirius Plössls, 25mm and 10mm, are standard equipment. The 25mm provides 48x, with a 1.08° field, more than twice the diameter of the full Moon, for expansive deep space views of nebulas, galaxies, and open star clusters. The 10mm provides 120x, with a 0.43° field, for close-ups of the Moon, planets, binary stars, and globular star clusters. Collimating tool: A pinhole-type collimating cap is supplied to fit in the focuser for quick alignment of the primary and diagonal mirrors. An optional battery-powered laser collimator is available for more precise alignment.
This Telescope’s Mount . . . Dobsonian mount: The Dobsonian altazimuth mount base has cutouts in each side board and a triangular ground board (rather than circular) to reduce the weight of the base to only 21.3 lbs. The base has a convenient carry handle and an eyepiece rack that can hold three 1.25" eyepieces and one 2" eyepiece. The particle board base is shipped disassembled and needs to be assembled only once, unless you disassemble it to save space for long-term storage. The assembly process takes about 30 minutes and requires, in addition to the supplied tools, a Phillips screwdriver and two adjustable crescent wrenches. You can substitute a 10mm crescent wrench for one of the adjustable crescent wrenches, or use a pair of pliers. Altitude and azimuth bearings: The 5.75" diameter altitude bearings rest in ultra-high molecular weight (UHMW) polyethylene pads for smooth vertical motion. The azimuth bearing uses Teflon bearing pads for equally smooth “stiction-free" horizontal motion. CorrecTension balance system: The springless adjustable tension system uses a simple “disc brake" to apply the correct level of tension to the altitude bearings to balance the weight of different eyepieces. With the CorrecTension system, you can change eyepieces or add a Barlow lens without having to hold the tube in place in altitude by hand or tediously adjust the telescope’s balance with counterweights as you do with other Dobsonians when the eyepiece weight changes. Simply turn the large CorrecTension knob slightly until the tube neither rises nor sinks when you change eyepieces and you’re done. The altitude friction can be made equal to the azimuth friction, ensuring smooth one-hand slewing to any part of the sky.
This Telescope’s Computer Hand Control . . . IntelliScope Object Locator: The IntelliScope hand control’s coiled cord plugs into a port in the side of the mount base, below the CorrecTension knob. A supplied aluminum holster attaches to the base to store the hand control conveniently close at hand when it is not being used. Two magnetic 9,216-step high-resolution digital encoders in the base communicate with the hand control through the cord. The encoders tell the hand control the direction in which the scope is pointed.
The intuitive menu buttons on the hand control allow selection of objects by type (e.g., Planet, Nebula, Cluster, Galaxy) or catalog number (e.g., M57, NGC 253, etc.) Press the Tour button to select one of 12 tours of the best objects visible in any given month. Or, if you’re not sure what you’re looking at, use the ID button to find out what object you’re viewing. The backlit adjustable brightness two-line LCD screen provides information about the objects you see, including object type, common name (if any), magnitude, constellation, and a brief visual description.
When a target object is selected by using the illuminated numerical key pad, two directional guide arrows (altitude and azimuth) are displayed on the LCD screen. Numbers by the arrows show the distance to the selected object. Simply move the telescope in the direction of the arrows. As you do, the numbers count down the distance yet to go as you approach the object. When both numbers reach 0.0, the object will be visible in the eyepiece. Finding celestial objects is that easy with the IntelliScope! The telescope can also be used as a conventional non-computerized Dob if you want to try your hand at finding things without the IntelliScope.
The IntelliScope hand control is powered by an included and readily-available 9V transistor radio battery. The battery will last 30 to 50 hours with typical intermittent use. Using a dim illumination setting on the LCD screen will help conserve battery power. An adhesive-backed hook-and-loop fastener is provided for mounting the IntelliScope hand control on the telescope. An optional metal holster is available that positions the hand control at a more convenient height on the base. Initializing the IntelliScope for use: The IntelliScope set-up procedure is exceptionally easy. First rotate the telescope tube to the vertical position and press Enter on the hand control. Then do a simple two-star alignment, in which you point the telescope at two known bright stars that you chose from those shown on the four seasonal star charts in the instruction manual, Press Enter as you center on each of the two stars. That’s all there is to it. You’re done! The telescope is now properly oriented with the night sky and ready to find objects.
IntelliScope data base: There are more than 14,000 objects in the database, enough for a lifetime of observing. It contains 7,840 objects from the NGC catalog; 5,386 objects from the IC catalog; 110 objects from the Messier catalog; 837 interesting single, double, multiple, and variable stars; the 8 major non-Earth planets (if you’re a traditionalist and still want to include Pluto as a planet); and 99 user-defined objects such as visible asteroids and comets (whose coordinates are published monthly in Astronomy and Sky & Telescope magazines).
The IntelliScope has an RS-232 port for cable connection to a computer. This allows you, with the appropriate software, to display a star chart on your computer screen that shows exactly where your scope is pointing and what interesting objects are in the vicinity for you to observe.
What can you see though the Orion SkyQuest 8XT? Under dark skies, the Orion Nebula becomes a glowing complex of filaments that more than fills the 1.08° field of the scope’s standard 25mm Sirius Plössl eyepiece. With over 800 times the light-gathering ability of even the sharpest dark-adapted eye, the SkyQuest XT8 makes nebulas and galaxies stand out briskly and in surprising detail, while the IntelliScope hand control makes it easy to find them by the hundreds. Binary stars and clusters are often resolved almost to the core because of the scope’s very good resolving power. Messier, NGC, and IC objects show detail and structure never visible in smaller telescopes. As with any large aperture telescope, the performance of the 8" SkyQuest on faint objects will be markedly improved by a dark sky observing site. While usable from light-polluted city and suburban sites, such sites are not ideal as the primary observing site of an 8" scope. Such sites require a nebula (light pollution) filter to avoid having deep sky objects washed out by the glare of city lights. Within the solar system, the rings of Saturn are routinely visible with the standard 25mm eyepiece at 48x, as are lunar mountain ranges and craters by the hundreds. At higher powers, Cassini’s Division in Saturn’s rings is often resolved, while the ring system itself is a magnificent sight. Given suitably good seeing, Encke’s Division and other minor features in Saturn’s rings occasionally become visible, for example, as does the faint crêpe ring. Low contrast details in Saturn’s atmosphere begin to make themselves apparent, as well. The standard equipment supplied with the SkyQuest XT8 makes it a complete working telescope for a visual astronomer – whether it’s your first scope or a step-up from a smaller scope. You can set it up and start observing almost as soon as it arrives. Photography is not possible with this manually-operated Dobsonian telescope. The 8" Orion SkyQuest XT8 is designed for visual observing only – to show you as much of the night skies as possible. It does it very well indeed, at a surprisingly affordable price.
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