SkyQuest™ XT8 IntelliScope™ 8"/20cm f6 Dobsonian Telescope

The Orion SkyQuest™ Dobsonian telescopes are designed for beginners who seek the best possible view of the planets, Moon, and faint Deep Sky objects while on a constrained budget. These telescope benefit from years of study and refinement of those Dobsonian style telescopes already on the market, including advanced design and materials to keep them lightweight and simple to use. Furthermore, the accessories included are common sense items to insure a good first night out; these are items that would normally be optional with competing telescopes.

While the original Orion SkyQuest™ XT8 telescope became the most highly recommended production 8" Dobsonian style telescope, and were the reference standard for its type at Company Seven, Orion simply couldn’t leave well-enough alone. Orion took the Dob that earned “best of the batch” honors from "Sky & Telescope" magazine (Jan. 2000) and enhanced it with even better engineered features and accessories!

Right: Orion SkyQuest™ XT8 IntelliScope™ Telescope with standard 9x 50mm Finder, 2" Focuser, Navigation Knob, 2" Carrying Handle, and 1.25" Eyepiece Holder (51,107 Bytes). Note the IntelliScope™ Control shown here is optional. Click on image to see enlarged view (85,940 bytes)

Our Orion SkyQuest telescopes always provided you with more bang for the buck, backed by Orion and Company Seven - two of the most credible and competent sources of telescopes in the marketplace. Now the SkyQuest XT8 IntelliScope™ continues its dominance over all other 8" Dobsonians worldwide by virtue of its superior engineering; for 2003 we add a new contemporary lightweight base design and most exciting of all, the ability to locate any of more than 14,000 fascinating celestial objects with pushbutton ease!

This telescope provides 48 inch focal length (f6 focal ratio), it is a versatile choice for amateur astronomy. This is part of the equation that provides good portability while retaining a good range if useful magnifications. The 8" aperture model is our most popular "first telescope" Dobsonian reflector, particularly attractive among those who desire an easily manageable telescope with the light gathering and fields of view potential to recognize many of the most popular deep sky objects (Galaxies, Star Clusters, Nebulae, Planetary Nebulae, etc.).

And yet this telescope affords the good contrast and clarity qualities required for lunar and planetary observing which actually may show changes through out an observing season. With a comparatively small central obstruction, and fewer optical surfaces, the contrast and brightness can actually surpass more expensive and complicated designs such as the 8" Schmidt-Cassegrain telescope.

What characterizes a Newtonian reflecting telescope?: The optical arrangement of this Orion optical tube assembly (OTA) is known as a "Newtonian". While an English mathematician originated this optical concept, it was Sir Isaac Newton who first made a working model in 1668, and he continued refining the design well into at least 1671. The Parabolic "Primary" mirror (illustrated below) is the factor by which most telescopes are described; hence an 8" telescope has a primary mirror of 8 inch (203mm) in diameter. The Primary mirror of the telescope is precisely mounted in a Cell (or mirror holder) at the rear of the telescope.

Right: Optical arrangement of Newtonian Reflecting telescope (38,882).
Click on image to see enlarged view (187,513 bytes)

The light entering the telescope is gathered and then reflects forward in a converging beam, to the elliptical Secondary Mirror that is positioned near the front of the telescope. This Secondary Mirror is supported in a tilted position so that to the light path the obstruction appears circular. The Secondary Mirror diverts the light from the Primary Mirror to the side and beyond the Focuser. The Secondary Mirror is attached to an adjustable Mirror Cell, and this assembly is held in place by a new (improved Oct. 2001) four vane Spider; this assembly is shown above and to the left as seen from the front of the telescope. The light from the Primary mirror is then reflected out to the side of the telescope achieving focus at a point beyond the focuser. An eyepiece for viewing, or camera for photography is placed at the focuser.

Left: Parabolic Primary Mirror of an Orion Dobson telescope in it's Cell (12,056 bytes).

Among the considerations of a reflecting telescope is that the mirrors be precisely positioned within the OTA in terms of centering, tilt, and spacing. The overall alignment ("collimation") of the one optical element to the other, and their placing the focal plane (the point where the image comes to focus) at the correct position beyond the focuser are critical. The optical axis of the telescope should be closely parallel to the mechanical axis of the tube assembly too.

Company Seven chose Orion's SkyQuest™ telescopes in part because of their consistently well engineered, good quality mechanical components, and partial assembly at the factory that facilitate collimating these telescopes precisely upon delivery, if needed.

Right: Orion SkyQuest™ XT8 Intelliscope Dobsonian Reflector front showing Secondary Mirror Holder and Spider, and Navigation Knob (36,519 Bytes). Click on image to see enlarged view (101,603 bytes)

A well made reflecting telescope can offer the best view per the dollar of the faint, deep sky objects where light gathering power is essential. Light gathering power increases are more important and come quicker than one may think; consider that a 6"f8 reflecting telescope may show objects about 335X fainter than the unaided eye, while an 8"f6 may offer 600 to 650X the light gathering power over the unaided human eye - in astronomy size can matter!

The Dobsonian telescope is characterized by its' simple to use Alt-Azimuth mounting, a lightweight primary mirror and modestly priced components. This concept was developed in the 1970's from San Francisco sidewalk astronomer John Dobson. His goal was to get the most telescope possible into the hands of the amateur observer for the lowest relative cost. This arrangement has since become known as the "Dobsonian" or "Dob".

The Dobsonian telescope consists of an optical tube assembly riding on a wooden alt-azimuth platform. The optical tube may be made of tube up to 18 or 20 inches in diameter. These tubes are typically made of Sonotube/cardboard, or plastic, or rolled metal. The Orion XT telescopes employ a rolled steel enameled tube finished internally in an anti reflection paint, with the exterior in a contemporary deep bronze metallic enamel. This tube holds optical collimation well even with temperature or humidity changes. This thin wall tube permits the designer to select a smaller secondary mirror/obstruction. And this keeps the tube lighter weight and more compact than heavier Sonotube tubes. In the case of the better made larger Dobson telescopes (12-1/2 inch and larger), a Truss arrangement is employed in order to facilitate disassembly into a more manageable and compact package. Our best-made Dobson telescopes up to 10 inch aperture are those offered by Orion. While our larger Dobson telescopes include the Truss tube telescopes made by Astro-Systems.

Working with Gravity: The center of gravity lies directly over the center of rotation in both directions, so no matter to where the telescope is pointed, the weight is evenly distributed through the mount to the ground. This characteristic, and sound design results in almost complete elimination of unwanted vibration and oscillation; the inevitable downfall of many poor telescope mounts. Whereas in many economical telescopes the image seems to bounce around forever after the scope has been touched, this is not the case with well made Dobsonians.

In addition to getting some help from Newton's Law, Orion engineers developed and now refined the original CorrecTension Friction Optimization system. This new system is a mechanism to adjust the tension or drag on the altitude bearings to compensate for varying loads of eyepieces, cameras, finders, etc.

Bearings molded from ultra-high molecular weight (UHMW) polyethylene and Teflon provide silky smooth motion of the telescope on both axes.

Orion's engineers not only streamlined the rock-stable Dobsonian base, but they also provided a lighter weight contemporary structure to the Base Side Arms.

IntelliScope™ Larger amateur Dobsonian telescopes often incorporate setting circles as an option which are helpful for locating objects by their cataloged coordinates. Many people find the beauty of a Dob is in their no-frills simplicity - they just work however, the modularity of the IntelliScope™ give you the choice. The IntelliScope™ system provides the user of the telescope the ability to quickly locate any of more than 14,000 fascinating celestial objects that come up in the Northern and Southern hemispheres with pushbutton ease!

Right: XT8 IntelliScope™ pointing to M5 Star Cluster by Bob Fuller, M8 Nebula by Coombs, and M33 Galaxy by Lorenzi. (127,639 bytes). Click on image to see enlarged view (268,752 bytes).

The IntelliScope™ system is an advanced form of digital setting circle providing a digital readout of position, with information about celestial objects in the database. This system features an electronic position indicator (Encoder) which is affixed to each of both axes of the telescope Base (or Carriage). The Azimuth (left-right) motion Encoder is provided with each Intelliscope Base when you buy the telescope. As you assemble the Base you may install the Azimuth Encoder, or if you pick up the telescope at Company Seven then you may have the instrument assembled with the Encoder(s) already installed for you. To activate the full benefits of these "digital setting circles" all one needs to do is buy the optional IntelliScope™ Computer Controller, install the provided Elevation (up-down) Encoder onto the Base, plug in the IntelliScopeª Computer Controller, and go!

Left: IntelliScope™ Controller with Cable (32,298 bytes). Click on image to see enlarged view (56,680 bytes).

When the IntelliScope™ series telescopes were introduced in 2003 the IntelliScope™ Computer Control system was an option, so the telescope could have been ordered with or without this system. But since virtually everybody who buys these telescopes wanted the IntelliScope™ control and encoder system, the IntelliScope™ Computer Control is included as standard equipment with each new IntelliScope™ telescope. This makes locating and viewing even the most elusive deep-sky curiosities becomes a "no brainer." Just select an object to view from the controller's database. High-resolution, 9,216-step digital encoders integrated in the telescope then pinpoint the object and the display guides the operator to point the telescope right to it. The backlit LCD display facilitates reading the information, and preserving night vision. Choose from dozens of additional menu options, including tours of the best deep-sky gems each month and identification of any object in the field of view.

The SkyQuest XT8 IntelliScope gives amateur stargazers speedy access to manually quickly guide their telescope onto a diverse catalog of celestial objects which appear with the push of a button on the optionally available IntelliScope Computer Controller. If you want to view the Whirlpool Galaxy? Then press the button labeled "Messier" ... select M51 ... and whoosh! Wow! In seconds, there it is, dead center in the eyepiece. If you have never been able to find that edge-on galaxy NGC 891, tap the "NGC" button, select 891 ... and again whoosh! You're there. It's that easy to locate and view object after object - so many more in an evening than most people could ever find before. For any astronomer seeking serious adventure, the XT8 has it all!

Full IntelliScope™ object-location functionality can be added at any time with purchase of the optional plug-in Controller.

The XT8 Base includes a convenient Eyepiece Accessory Tray. This standard eyepiece holder is provided with slots for up to three 1.25 inch accessories, and one of 2" diameter. Furthermore, this tray is held in place by two keyhole shaped screw holes so that customers may easily slide the tray up and out to remove the tray for transport or if desired. To keep dew or other contaminants from marring eyepieces set on thi