Maksutov-Cassegrains

More Information  · Supplied Accessories  · Recommended Accessories  · Related Documents  · Images of Some Features Price $599.00 Supplied Eyepiece SP26 Highest Useful Magnification 186x Visual Limiting Magnitude 11.7 Focal Length 1250mm Focal Ratio f/13.8 Resolution 1.3 arc seconds Aperture 3.5" Weight 21 lbs. Heaviest Single Component 12 lbs. Warranty 1 year

This Telescope’s Optical System . . .

• Maksutov-Cassegrain optics: 90mm (3.5") aperture, 1250mm focal length, f/13.8 focal ratio. The meniscus corrector lens is Grade-A BK7 optical glass. The primary mirror is low-expansion Pyrex. Guaranteed diffraction-limited optical performance.

• Multicoated UHTC (Ultra High Transmission Coatings) optics: The primary mirror and secondary mirror spot on the rear of the meniscus corrector lens are coated with highly reflective aluminum enhanced with a complex stack of multi-layer coatings of titanium dioxide and silicon dioxide. Both aluminized surfaces are overcoated with quartz for long life. There are antireflection multicoatings on both sides of the Maksutov corrector lens. These UHTC optics have up to 20% higher light transmission than Meade standard optical coatings. This adds the equivalent of a third of an inch of additional aperture to the scope’s light grasp, for brighter deep space images. It also improves contrast, for sharper lunar and planetary images.

• Excerpts from a review of the optics: In a review of the original ETX-90, which had identical optics to this new model (why change a good thing?), Sky & Telescope magazine said, "The optics in our test telescope were excellent . . . Star images came to a precise focus . . . The Moon was beautiful at any magnification, with black shadows contrasting sharply with illuminated features along the terminator. Venus appeared dazzlingly white with no color fringes except those caused by atmospheric refraction. Like Venus, Jupiter was low in the January evening sky, but several bands were easily seen on the planet's disk . . . Saturn was very impressive. As the planet snapped into focus in the supplied 26-mm (48x) eyepiece, I could easily see the rings' Cassini Division and several bands on the ball of the planet . . . The bottom line is that the ETX-90 showed me everything I could expect from an instrument of its size."
      While the ETX-90PE’s aperture limits the number of deep sky objects visible, those that are within its magnitude 11.7 light grasp stand out crisply against a dark sky, particularly multiple star systems, globular clusters, and compact planetary nebulas.

• Dust covers: A thread-in metal dust cover protects the meniscus lens. A thread-on metal cap seals the Cassegrain focus on the rear cell.

• Finderscope: A straight-through wide-field red dot SmartFinder allows easy non-magnified views of the sky, with a projected red dot of light showing exactly where the scope is pointed at all times.

• Star diagonal: Built-in first surface flip-mirror. For astronomical observing, the internal flip-mirror directs the image to the 26mm Super Plössl eyepiece in the eyepiece holder at the top of the scope. Touch a lever, and the flip-mirror redirects the image through the Cassegrain focus at the rear of the scope to an optional #64 T-adapter and T-ring for lunar or terrestrial photography, or to an optional #932 45 degree viewing angle image-erecting diagonal for upright and right-reading terrestrial viewing.

• Eyepiece: 1.25" 26mm Series 4000 Super Plössl (48x) specially modified to fit the scope's low profile eyepiece holder. The eyepiece field of view is 1.04 degrees, more than twice the diameter of the full moon.

This Telescope’s Mechanics and Electronics . . .

• Dual fork arm altazimuth mount: The optical tube is aluminum, finished in classic Meade blue. We conducted an on-line survey for Meade a few months back, in which visitors to our site voted for their favorite Meade color scheme. The voting showed that many Meade fans still preferred an understated Meade blue tube to the full-color photo of the Orion Nebula (M42) that wraps around the tube of the astro version of the ETX-90 Premier. Meade listened, and Meade changed. Now you can have whichever tube trim suits you best – this Meade blue tube or the astrophoto tube version (#MP3U). Either way, you still get sensational ETX Maksutov optics inside the tube.
      The rear cell, fork arms, and drive base are durable metal-reinforced injection-molded plastic that helps keep the cost of the 90PE very reasonable. While the molded parts of the 90PE are quite rugged, a little extra care in setting up and using the scope might be prudent.
      There are three rubber feet on the base of the scope. These allow the 90PE to be placed on a suitably sturdy tabletop or flat surface for casual computerized observing without having to set up the supplied full length field tripod.
      The mount includes built-in right ascension and declination DC drive motors so the supplied Autostar computer can automatically track objects. The motors are powered for up to 20 hours by eight AA batteries (not supplied) that fit into an internal battery compartment in the telescope base. They can also be powered by optional #541 AC/DC or #607 DC adapters.
      When used in the default altazimuth mode on table or tripod, the supplied Autostar computer hand control moves the scope in any of four directions (right/left, up/down) at any of nine speeds. The speeds range from 2x the sidereal rate for guiding, up to 5 degrees per second for locating objects and slewing, plus the sidereal rate for automatically tracking objects under the control of the computer. No manual slow motion controls are provided – or needed. When set up on the supplied tripod for equatorial (polar) operation, the Autostar computer converts the right/left, up/down altazimuth directions to motions in right ascension and declination to correspond with the coordinates of objects on the celestial sphere.

• LNT (Level North Technology): The ETX-90PE contains an electronic level sensor, an electronic magnetic North sensor, and a high precision internal clock. These components combine with the Level North Technology software to make aligning on the sky as easy as remembering your own zip code. Simply take the scope outside and set it up on a level surface or on its supplied tripod. Tell the scope your location – either your latitude and longitude or your zip code. The scope will use its built-in level and magnetic North sensors to level the optical tube and point it North. The internal clock will tell the software the correct time. The software determines where and when on earth it is and what the sky looks like overhead. It then moves the scope automatically to an alignment star. If the star is not precisely centered under the red dot in the SmartFinder, you can use the Autostar hand control pushbuttons to center it to improve the pointing accuracy. Let the scope repeat the process for a second alignment star and you’re ready to start observing. The LNT system makes using the scope almost as easy as using a costly GPS-equipped telescope, but at a fraction the price.

• Autostar computer hand control: The standard equipment #497 Autostar computer automatically slews to, and tracks, more than 30,000 near and deep space objects (although not all will be visible due to the 11.7 limiting magnitude of the scope’s 3.5" aperture). The objects include all 110 of the Messier objects; the complete 5386-object IC catalog, the complete 7840-object NGC catalog, the complete 109 object Caldwell catalog of the best objects for small telescopes; 16,800 stars from the SAO catalog including double starts, variable stars, and other stars of special note; the planets; 26 of the brightest asteroids; 15 periodic comets; 50 earth-orbiting satellites; the centroids of all 88 constellations; plus user-defined objects and guided tours around the sky.
      The Autostar hand control gives you a digital readout of r. a. and dec coordinates; scrolling information about the object being viewed; plus the results of calculations about sunrise, sunset, moonrise, moonset, moon phases, solar eclipses, lunar eclipses, the minimum of Algol, and more. Hypertext links on the Autostar screen display define many of the terms used in the computer (there's more than one megabyte of compressed text stored in the Autostar.) Built-in guided tours of the sky are tailored to the day of the year you are observing. They direct you to showpiece objects, including the Moon and any planets then visible. Most of the tour objects are accompanied by descriptions scrolling across the Autostar display (the description of Algol, for example, is over 300 words long). The Moon has different descriptions based on its phase, and prominent features near the terminator are highlighted.
      On-screen operation instructions guide you through setup and use of the Autostar and a help function is only a keystroke away. Objects can be accessed by their catalog number or by their common name. An RS-232 port in the Autostar allows you to control the 90PE remotely from a PC, using Meade’s the supplied Autostar Software Suite and PC to scope cable. The software and optional cable also allows you to download free Autostar software upgrades from Meade’s website.
      The Autostar can operate in an altazimuth mode, with the 90PE sitting on a table or any suitable flat surface. The scope can also operate in a polar mode, using the standard equipment #884 deluxe full-length adjustable height field tripod. Motor noise is quite audible when tracking objects in the altazimuth mode and may be objectionable to some people. Most people will probably prefer the quieter tracking of polar operation using one of the tripods mentioned above. Slewing to an object is relatively noisy in either mode of operation. However, most people consider this to be a small penalty to pay for the convenience of fully computerized go-to operation.
      Pointing accuracy of the Autostar computer is good in either mode. The Sky & Telescope review noted that they used the "Autostar's internal catalog and the Go To function to slew to more than a dozen bright stars scattered around the sky. All but one lay well within the 1 degree field of the 26-mm eyepiece"
      The drive direction can be temporarily reversed for southern hemisphere use by a few keystrokes on the hand control. This allows you to operate the ETX-90PE anywhere in the world. Other keystrokes change the scope’s default tracking from an altazimuth to a polar mode.

• Autostar Software Suite (Astronomer Edition): This supplied software/hardware package consists of a planetarium/telescope control program and a cable to connect the ETX-90PE to your PC or laptop. The Autostar Software Suite (Astronomer Edition) is designed to integrate your telescope with a Windows-based PC or laptop computer for an enhanced range of performance features.
      It includes a planetarium program with a database of 19,000,000 stars and deep space objects to display on your computer screen. The program has all the display and star chart-printing features of an advanced planetarium-type software program for stand-alone use when nights are cloudy. If you connect the scope to your computer or laptop (using either the supplied cable), the program lets you click on objects in the sky map display on the computer screen and have your 90PE automatically slew to those objects.
      The software lets you control all Autostar functions from your computer or laptop. You can use it to create observing lists with a simple point and click and download them to the Autostar for use in the field when you don’t have your computer or laptop with you. You can use it to control your telescope remotely via the Internet. “Talking Telescope" software (included) converts the Autostar’s text displays to synthesized speech and plays it through your computer speaker. An Autostar Update Tool keeps your Autostar current by downloading the latest system firmware updates and comet, asteroid, and satellite data from the internet.
      The minimum computer requirements for installing the Autostar Software Suite are a PC running Windows 98SE or better, with 64 MB of RAM, and 100 MB of free hard disk space.

• Adjustable height tripod: The supplied full-length Meade #884 Deluxe Field Tripod provides a rigid mounting platform for virtually any observing application, astronomical or terrestrial. It can be used for either standing or seated observing. The #884 has tubular chromed steel legs and is adjustable in height from 26" to 44" when used in the altazimuth mode. It has a built-in equatorial wedge with an integral latitude scale and no-tool latitude (altitude) adjustment for use at any observing latitude between 20° and 90°. The 90° (altazimuth) position is for terrestrial observation and for quick set-up astronomical observing. Setting the wedge tilt plate to your observing latitude and aligning the scope on the celestial pole allows more accurate object location and sidereal rate tracking, but takes more time to set up.
      The ETX attaches to the tripod in seconds using two thumbscrews in the wedge tilt plate. The thumbscrews are tethered and spring-loaded so they can’t be lost in the field. The spreader bar that holds the legs open is spring-loaded as well, so setting up and taking down the tripod takes only a few seconds. There are six 1.25" diameter holes cut into the spreader bar to hold 1.25" eyepieces. The tripod comes with a padded Cordura-style carrying case with carry handle, shoulder strap, and an external zippered pocket for the spreader bar.