LX90-ACF 10" Advanced Coma-Free Go-to altazimuth

The software lets you enable or disable the Hubble Guide Star Catalog; set the on-screen Viewpoint to go to the current zenith or any R.A. and Dec. coordinate; choose any object by catalog name or number; enable or disable custom catalogs; add new catalogs; set magnitude limits; flip the star map for correct orientation as you observe through the telescope; zoom the star map display from 180° down to tiny fractions of an arc second; adjust label fonts and colors, coordinate grid colors, and brightness and contrast; enable or disable the night vision mode; and more.

In addition, if you connect the scope to your computer, the program lets you click on objects in the sky map that is displayed on the computer screen and have your telescope automatically slew to those objects. You can automatically generate AutoStar Tours of favorite objects with a simple point and click, as well as using the program to keep observing logs.

The software lets you control all AutoStar functions from your computer or laptop. You can use it to create observing lists and download them to the AutoStar for use in the field when you don’t have your computer or laptop with you. “Talking Telescope” software (included) converts AutoStar text displays to synthesized speech through your computer’s speaker. An AutoStar Update Tool in the software keeps your AutoStar II computer hand control current by downloading the latest system firmware updates and comet, asteroid, and satellite data from the internet.

You can also use the software to control your telescope remotely via the internet. Designed to be the ultimate platform for remote digital astronomy with your Meade telescope, the AutoStar Suite Astronomer’s Edition contains tools for dome controls, weather sensors, and other functions required for this purpose. You can reach your telescope and dome through a single network connection. You can then communicate via an IP address, using the AutoStar Net Scope program to control the entire observatory over the Internet. This solves the biggest problem in setting up for remote access to your telescope – the problem of your distance from the scope itself. You can be in your living room to control the scope in your backyard, or just as easily, control a friend’s system in another country!

The minimum computer requirements for installing the AutoStar Suite Software are a PC running Windows 98SE or later, with a minimum of 64 MB of RAM, and 200 MB of free hard disk space.

The LX90’s AutoStar computer hand control plugs into the telescope’s fork arm to permit a wide array of telescope options. First and foremost is its automatic go-to capability. The AutoStar computer can show you the planets and thousands of deep space objects the very first night you use your scope – even if you've never used a telescope before! At the push of a button, the LX90 will move at a fast 6.5° per second to any of the 30,223 objects in its database. You can choose from 13,235 deep-sky objects from the complete Messier, Caldwell, IC, and NGC catalogs (sorted by name and type). Also included are 16,888 stars sorted by name, SAO catalog number, and by whether they are double or variable stars.
    The AutoStar will also locate the centroids of all 88 constellations and 50 objects in the solar system (8 major planets from Mercury to Pluto; the Moon; 26 asteroids; and 15 periodic comets). You can use it to track 50 Earth satellites, including the International Space Station, the Hubble space telescope, and Mir, plus any of 200 user-defined objects. You can also automatically move to any object that’s not in the database simply by entering its right ascension and declination coordinates. The AutoStar moves the LX90 at any of nine user-selectable slewing and guiding speeds: 6.5°/sec, 3°/sec, and 1.5°/sec for slewing and centering; as well as 128x, 64x, 16x, 8x, and 2x the sidereal rate for centering and astrophotographic guiding. In addition, there are standard lunar and sidereal tracking rates, plus a user-defined drive rate for precision tracking of the Sun and planets. The AutoStar includes a Smart Drive dual-axis drive corrector for long-exposure guided astrophotography (when used with an equatorial wedge in the polar mode). The Smart Drive has permanent periodic error correction that can be trained for finer and finer drive accuracy. You can even connect an optional #909 accessory port module to the rear cell of the LX90 to allow completely automatic CCD autoguiding of long exposure photos. The #909 also allows the use of an optional electric focuser and illuminated reticle eyepiece.
    The AutoStar computer includes hundreds of special event menus, guided tours, a glossary, utility functions, and telescope status options. It also allows fast alignment of the telescope in either an equatorial or altazimuth mode using any of three alignment methods, including Meade’s proprietary Easy Align method.
    The altazimuth drive of the LX90 is more than accurate enough for piggyback, lunar, and planetary 35mm photos and much CCD imaging. However, field rotation causes stars at the corners of an image to streak during exposures longer than five minutes if you don’t use an equatorial wedge to align the scope on the celestial pole. So, if you plan on doing long exposure deep space photography, you'll need to add the optional #2590 LX90 equatorial wedge to your 8” scope, and the #2570 Ultrawedge to your 10” or 12” scope.

A 16-channel Sony GPS (Global Positioning System) receiver is built into the top of one of the fork arms. When the scope is turned on, the GPS receiver locks onto the network of orbiting GPS satellites to determine your observing location’s latitude, longitude, date, and time. It uses this information to tell the scope’s AutoStar computer where and when on earth the scope is located. Once the computer has this information, it orients the scope to the sky and slews at 6.5 degrees per second to the first of two alignment stars. If that star is not precisely centered in the finderscope or main scope optics, a touch or two on the Autostar hand control’s directional push buttons quickly centers it. Do the same with the second alignment star the scope moves to and the scope is then accurately aligned on the sky and ready to locate and track any celestial object you choose.

The mount includes servo-controlled 12VDC slewing and tracking motors with 4.9” worm gear drives in both altitude and azimuth. The drive system has individually selectable drive speeds in both right ascension and declination – 6.5°/sec, 3°/sec, and 1.5°/sec for slewing and centering; as well as 128x, 64x, 16x, 8x, and 2x the sidereal rate for centering and astrophotographic guiding. In addition, there are standard solar, lunar, and sidereal tracking rates with 2000 precision-selected incremental rates that permit observatory-level precision in tracking the Moon and planets.

The scope is powered by eight user-supplied C-cell batteries that store in the drive base so you can use the LX90 in the field or your backyard without the need for a separate battery pack or AC power supply. The usable life of the batteries is up to 60 hours, depending on the ambient temperature (colder temperatures reduce usable battery life). An optional #RCXAC adapter is available to allow you to power the scope from 110-120volt 60Hz AC household current in your backyard to conserve battery life. An optional #607 cigarette lighter plug cable is available to power the scope from your car's cigarette lighter plug or from a rechargeable battery for extended use in the field.

• Advanced Coma-Free catadioptric designed to emulate the optical performance of a Ritchey-Chrétien telescope: The traditional two-mirror Ritchey-Chrétien (RC) design uses approximately hyperbolic primary and secondary mirrors to produce images that are free from coma over a wide field. Because of this wide coma-free field and a relatively fast focal ratio, the Ritchey-Chrétien design is particularly well suited to astrophotography. The RC is the design of choice for most of the major professional observatory telescopes built in the last half-century. For example, the Hubble Space Telescope and the twin 10-meter Keck telescopes in Hawaii are Ritchey-Chrétiens.
      However, because of the complexity of fabricating and testing a large aperture hyperbolic mirror (just ask the people who built the initially-flawed, but not discovered until it was in space, Hubble Space Telescope), traditional two-mirror Ritchey-Chrétiens are very expensive to manufacture and purchase, too expensive for many amateur astronomers.
      To emulate the coma-free performance of a true RC telescope, while keeping the cost very much within reason, the LX90-ACF Advanced Coma-Free (ACF) catadioptric optical system uses a full aperture aspheric corrector lens in conjunction with a simple spherical primary mirror. This creates a two-element primary mirror system that performs like an RC’s single hyperbolic primary mirror from the optical point of view of the LX90-ACF secondary mirror. The hyperbolic secondary mirror itself is mounted directly on the rear of the corrector lens, rather than in the traditional RC’s conventional spider vane assembly. This eliminates the image-degrading diffraction spikes of the secondary mirror support structure visible in commercial RC scope images. The result is RC-class coma-free wide-field performance in the LX90-ACF, at about a fifth the cost of most true RC systems.
      The corrector-modified design would itself be expensive to fabricate were it not for Meade’s more than a quarter-century of experience making Schmidt-Cassegrain correctors, which are in the same optical family as the corrector needed for the coma-free design of the LX90-ACF. An additional benefit of the full aperture corrector in the ACF design is slightly better correction for astigmatism than the traditional RC design.
      In addition, the LX90-ACF, due to its front corrector plate, is a closed tube design. This keeps the primary optical components protected from dust, moisture and other contaminants that might fall on the optical surfaces of the primary and secondary mirrors as can happen with the traditional open-tube RC design.
      While the LX90-ACF may not be a traditional RC design, its performance is RC-like in all important characteristics. A review in Sky & Telescope magazine of the ground-breaking predecessor of the Meade ACF optics said the bottom line is that the optics do “indeed perform like a Ritchey-Chrétien.” Another such review, in Astronomy magazine said, “This scope delivers Ritchey-Chrétien-like performance at a fraction of the cost.”

• Oversized primary mirror: The diameter of the primary mirror of each LX90-ACF is larger than the diameter of the corrector lens at the front of its optical tube that admits the light. The primary mirror of the 8” scope is actually 8.25” in diameter, compared to the 8” diameter of the corrector lens. The 10” primary is 10.375” in diameter, and the 12” is 12.375” in diameter. Oversizing the primary mirror in this way gives you a wider fully-illuminated field than a conventional catadioptric scope whose corrector and primary mirror are the same size. The result is a gain of 5% to 8% more off-axis light available to your eye or camera, depending on the telescope model.

• Fully multicoated UHTC (Ultra High Transmission Coatings) optics: The primary and secondary mirrors are vacuum-coated with aluminum, enhanced with multiple layers of titanium dioxide and silicon dioxide for increased reflectivity. A overcoating layer of durable silicon monoxide (quartz) assures long life.
      A series of anti-reflective coatings of aluminum oxide, titanium dioxide, and magnesium fluoride are vacuum-deposited on both sides of the full aperture corrector plate. These antireflection multicoatings provide a high 99.8% light transmission per surface, versus a per-surface transmission of 98.7% for standard single-layer coatings. Overall light throughput (the amount of light collected by the objective lens that actually reaches your eye or camera) is approximately 89% at the focal plane.
      UHTC multicoatings provide a 15% increase in light throughput compared with standard single-layer coatings. They effectively add the equivalent of 15% extra light-gathering area to the performance of a scope with standard coatings. It’s the equivalent of three-quarters of an inch of extra aperture in the case of a 10” scope, for example, but with no increase in actual size or weight. UHTC coatings also improve contrast, for lunar and planetary images that appear sharper and more crisply defined.

• Fully baffled optics: A cylindrical baffle around the secondary mirror, in combination with the cylindrical baffle tube projecting from the center of the primary mirror, prevents stray off-axis light from reaching the image plane. In addition, a series of field stops machined into the inner surface of the central baffle tube effectively eliminates undesirable light which might reflect from the inside surface of the tube. The result of these baffle systems is improved contrast in lunar, planetary, and deep space observing alike.