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Meade - 20" LX400-ACF (f/8) Advanced Coma-Free OTA


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A traditional Ritchey-Chrétien (RC) is a type of reflector that delivers a coma-free field of view via hyperbolic primary and secondary mirrors. RC telescopes (from a variety of manufacturers) are found in most of the world's top observatories and NASA's Hubble Space Telescope. Because the mirrors in these telescopes have always been very expensive to make, few amateur astronomers could enjoy them. Fortunately, Meade engineers developed a radical new Advanced Coma Free design by combining a hyperbolic secondary mirror with a corrector-lens-and-spherical-primary-mirror combination that performs as one hyperbolic element. This ACF design produces a coma-free, flatter field of view that rivals traditional RC telescopes at a fraction of the cost. The design even eliminates diffraction spikes and improves astigmatism, both of which are inherent in the traditional RC design. 



Meade has offered the 16" for years as an SCT on a fork mount. It has been the scope of choice for serious amateurs, colleges and teaching universities. Now you can have an Advanced Coma-Free optical system not only at 16" but at a full half-meter of aperture. This brings the MAX into the domain of serious research. There has been an outcry that observatories are moth-balling scopes in the 1/2 to 1 meter category to save funds to operate a few gargantuan telescopes at their facilities. This is sad because a search of the literature shows that the vast majority of good science is performed with telescopes in the 1/2 meter to 1 meter class.The MAX Mount with a 1/2 meter Advanced Coma-Free optical system brings a mass produced affordable research scope within the reach of almost any academic institution and many individuals. Remember that comet SL9 was discovered on an 18" scope. A well sited 1/2 meter scope will reach magnitude 19 with a Deep Sky Imager in under 1 minute. Magnitude 20 is achievable in 4 minutes

Optical Tube Assembly (OTA) 190 pounds L = 40"; W = 25.7"; H = 25.7"

Product Series

The ""advanced" in Advanced Coma-Free. A traditional Ritchey-Chretien (RC) is a type of reflector that delivers a coma-free, flat field of view via hyperbolic primary and secondary mirrors. RC telescopes (from a variety of manufacturers) are found in most of the world's top observatories and NASA's Hubble Space Telescope. Because the mirrors in these telescopes have always been very expensive to make, few amateur astronomers could enjoy them. Fortunately, Meade engineers developed a radical new Advanced Coma-Free design by combining a hyperbolic secondary mirror with a corrector-lens-and-spherical-primary-mirror combination that performs as one hyperbolic element. This Advanced version of the traditional RC design produces a coma-free, flat field of view that rivals traditional RC telescopes at a fraction of the cost. The design even eliminates diffraction spikes and improves astigmatism, both of which are inherent in the traditional RC design. When reviewing Meade's LX400-ACF Advanced Coma-Free, Sky and Telescope magazine said, " [It] does indeed perform like a Ritchey-Chretien. The difference between the off-axis images (compared to a Schmidt-Cassegrain) was dramatic to say the least."

f/8 Advanced Coma-Free Optics: The Ritchey-Chretien or RC optical design is well known to discerning astrophotographers and is the telescope optical design in many of the leading professional observatories of the world. By creating the Advanced Coma-Free design, Meade has taken the f/8 RC optical design to another level by adding a corrector plate to reduce residual astigmatism that is inherent in the traditional optical design. In addition many more design features were added to the LX400-ACF for the demanding researcher and imaging enthusiast with telescopes available in apertures of 10 inches, 12 inches, 14 inches, and 16 inches. Series 5000 24mm 2" O.D. Ultra Wide Angle Eyepiece: Standard equipment on all LX400 telescopes, the Series 5000 24mm 2" O.D. Ultra Wide Angle Eyepiece represents the ultimate in eyepiece design and technology delivering extremely high resolution, contrast and full-field sharpness over an astounding 82° apparent field-of-view. Only the highest quality materials were selected to create this extraordinary eyepiece. The designs required several different types of exotic glass in order to achieve the highest level of optical performance. New Carbon Graphite & Kevlar Tube: The carbon graphite and Kevlar tube is a unique light-weight, high strength material with ultra-low expansion characteristics that will maintain the spacing between the optics, so that focus settings do not change with outside temperature changes. This is a critical feature to astrophotographers. Instead of forcing a perfectly round shaped tube assembly, the tube is shaped around the mechanisms and drive system of the front focus and collimation assembly, giving the LX400-ACF its unique look and style. New Rear and Front Cell Architecture: The front and back cells of the LX400-ACF are designed to allow the maximum amount of air-flow around the optics, in order to achieve the quickest "cool down" times. To accelerate cool-down time, a built-in fan on the rear cell can be turned on and off through the AutoStar II handbox. The rear cell additionally incorporates a multi-port panel with 3 USB ports, a port for an autoguider, AutoStar II handbox, illuminated reticle, RS232, and one for future "Smart" accessories. LX400 Drive Base: The multi-port panel of the LX400 drive base includes a special single High-Speed USB 2.0 input port allowing simultaneous control over the telescope and either the Meade LPI or Deep Sky Imager camera through Meade's AutoStar Suite software. Additionally there are ports for a power cord input, the AutoStar II handbox, a DB-9 auxiliary port, 12v out power port, and RS-232. Additionally the LX400 includes the familiar on/off switch and LED power light indicator. New Ultra-Stable Tripod: Standard equipment for LX400 10", 12", and 14" telescopes, the patent pending trigger release leg locks of the Ultra-Stable tripod are positioned at the top of the tripod legs for easy access. ALL - NEW OPTICAL SYSTEM The LX400 Advanced Coma-Free Optical System It is generally accepted that the Ritchey-Chretien or Classical RC system is the premiere optical design for medium to large aperture astronomical telescopes. The primary benefit of a Classical RC is the fact that it is an aplanatic design which means it is coma-free. Coma is an optical aberration that causes star images to appear comet like with tails that point away from the center of the field of view. The further from the center, the larger the effect. Fast Newtonians suffer from this aberration the most, followed by other reflecting optical systems of various designs. The Schmidt-Cassegrain or Schmidt-Newtonian design typically has 1/2 the coma of a Newtonian of the same focal length. The Classical RC design uses a hyperbolic primary mirror and a hyperbolic secondary mirror to create an aplanatic optical system which has no coma. This system produces small round star images all the way to the edge of the field of view. Meade's engineering team recognized the advantages of the Classical RC design but explored the possibility of using Meade's unique engineering and manufacturing expertise to improve on the basic design. The result is the LX400 optical system which is also an aplanatic, coma-free design with small round star images to the edge of the field. The LX400 design is very similar to the Classical RC and achieves the same benefits by using a hyperbolic secondary with a new advanced front corrector plate and primary mirror that together perform as a hyperbolic primary. This design has several advantages over the Classical RC design. * The LX400 eliminates the secondary mirror holder support vanes (spider) that cause diffraction spikes. Because almost all reflecting telescopes produce diffraction spikes, many people are used to seeing them and don't consider them an aberration. But in reality, they are a large distortion that reduces image contrast, lowers resolution and presents an unrealistic view of the sky to the eye or the astro-imager. * The LX400 design reduces the amount of astigmatism that is inherent in the Classical RC design. * The LX400, due to the front corrector plate, is a closed tube design. This keeps the primary optical components protected from dust, moisture and other contaminates that might fall on the optical surfaces of the primary and secondary mirrors. While the LX400 optical system is as difficult to manufacture as a Classical RC, it was chosen because of its superior performance (i.e., no diffractions spikes, reduced astigmatism and closed tube). Due to Meade's years of experience in designing and manufacturing sophisticated corrector plates and optical systems, we are in a position that very few, if any, other companies enjoy. Applying this expertise and Meade's resources, we are able to produce this advanced optical system at a fraction of the price that other companies would have to charge, if they could produce it at all. Precision GPS Alignment: Telescope alignment is accomplished automatically using signals from the Global Positioning System (GPS), a satellite system that enables extremely precise communication to the telescope of the observer's latitude and longitude, as well as local time. Integrated True-Level and North electronic sensors in combination with a high-sensitivity Sony GPS receiver located in the left-hand fork arm result in accurate telescope alignment to the sky at the touch of a button: Just press the ENTER button on the Autostar II hand controller and watch as the telescope measures level, points North, and slews at 8°/sec. to its first alignment star. Magnetic declination compensation designed into the telescope software automatically engages during the alignment process. Software Downloads and Satellite Tracking: The software included in Meade LX400 telescopes is under continuous factory review; updates to this software are published at regular intervals on Meade's website. Importantly, the latest software version, as well as custom and updated guided tours, comet and asteroid positions, may be downloaded in minutes from Meade's website. Additionally, current Earth satellite orbital data (including the International Space Station, Space Shuttle, etc.) may be downloaded; the telescope then automatically acquires and tracks the satellite at the correct tracking rate. The telescope's flash memory may be upgraded through one of the RS-232 ports with new software or data as they become available on Meade's website. Expanded Database and Larger User Memory: The LX400 database has been expanded over the standard library of the LX200GPS to include 180,000 objects. In addition to more stars from the Hipparchos/Tycho catalog, we have added:: • The popular "Lunar 100" with the finest features to see and image on the Moon • A subset of the finest visual doubles from the Washington Double Star Catalog • The PK Catalog of Planetary Nebulae • The Hickson Catalog of Dense Galaxy Clusters • The Gleason Catalog of Nearby Stars • The Landolt Catalog of Photometric Standard Stars • The Sharpless Catalog of HII Regions Laser Aligned, Fixed Primary Mirror: The primary mirror is laser aligned to the true optical path, then float bonded in place. It is fixed, but literally floats on a layer of adhesive that results in zero stress to the glass and no distortion to the optics (unlike mirror cells or floating point pads). There is no mirror movement. Field Operation: LX400 scopes operate from eight C-cells neatly stored inside the fork arms. Alternately, telescope powering may be effected from an automobile cigarette lighter plug (using the optional #607 Power Cord) or from a standard home outlet (using the new optional AC Adapter). #929 2" Diagonal with UHTC: Standard equipment on all LX400 telescopes, attaches to the rear cell of and permits the use of wide-field 2" O.D. eyepieces. Each diagonal includes a Meade optical-flat mirror of Pyrex glass, UHTC-coated for maximum reflectivity. Built-In Dew Heater: Instead of wrapping a heating element around the telescope's optical tube assembly to send heat through the telescope's front cell to prevent dew from forming on the corrector plate, the LX400 incorporates a nickel-chromium wire heating element that is in contact with the glass of the corrector plate that quickly, efficiently, and safely sends heat through lens using the lowest power drain possible. With two onboard temperature sensors, one to measure ambient temperature (placed inside the fork arm) and one to measure the temperature of the corrector plate, the LX400 can be set to have the built-in dew heater keep the corrector plate warmed to a user-defined setting above ambient temperature. By only using the dew heater precisely when needed, battery usage is managed to its optimum. All functions to operate the dew heater are controlled by the AutoStar II handbox. Precision Encoder-Measured Digital Focusing: With a laser aligned primary mirror fixed in position, focusing is performed electronically and digitally by precisely moving the entire front cell in increments as fine as 1/100 of a millimeter. Digital readout of the focus position can be read on the telescope's AutoStar II handbox. There are 4 different focusing speeds from fine to fast. Since the process is accomplished without moving the primary mirror, the entire assembly is virtually free from image shift. High-Precision Pointing (HP) Capability: Meade LX400 models permit the most accurate pointing capability ever offered in a commercial telescope. Now you can command the telescope to GO TO an object located on the opposite side of the sky (for example, a distance of 120 degrees in sky-angle) and, in conjunction with the telescope's unique SYNC command, the LX400 locates and centers the desired object. HP capability is accessible in either the altazimuth or equatorial orientations. Precision Electronic Optical Collimation: Collimating a Cassegrain telescope has never been easier. LX400 owners will make precision collimation adjustments to the secondary mirror of the telescope by using the arrow keys of AutoStar II handbox, allowing a single person to simultaneously make adjustments and see the results. In addition, Meade precision collimates the optics at the factory and then sets that position as the default setting. So in the case where one may make a mistake in making a collimation adjustment, the default setting can always be used. Smart Drive Permanent Periodic Error Correction (PPEC): Included as standard equipment, the Smart Drive permits a professional level of drive-rate precision. No longer are large systems required, worm gear when smaller gears coupled to Smart Drive software can achieve periodic errors of 5 arc secs or less-an observatory standard of precision. All worm/worm-gear combinations, no matter how well made, have minor inaccuracies that manifest themselves as periodic errors in the telescope tracking rate, with the period dependent on the worm's rate of rotation. To program the Smart Drive the observer guides on an object visually, making corrections with the handbox controller. The software then remembers these corrections, stores them in memory, and in the future automatically compensates for the periodic errors of the gear system. Smart Drive user programming is stored in the telescope's computer memory forever, independently of any power source, unlike other periodic error correctors that must be reprogrammed each time you use the system. The Smart Drive can be erased, updated, or even averaged with future programming at the user's option. The significant value of the Smart Drive is immediately appreciated during long-exposure astrophotography, where the resulting low periodic error of the system enables relaxed guiding with a minimum of handbox corrections. In CCD imaging, where short exposures of deep-space objects are often all that is required for stunning results, the Smart Drive often permits imaging without any guiding requirements at all. Heavy-Duty Fork Mounts: LX400 fork mounts are the strongest, most rigid mountings ever made available for telescopes of these apertures. Fork arms, are both longer and stronger. This allows the 10", 12" and 14" scopes to go all the way to 90 degrees declination on a wedge, allowing you to reach the horizon. The increased fork size also gives more back clearance to allow imaging all the way to the pole with most cameras. DC-servo-motor-controlled (12v DC) worm gear drives with almost two hundred selectable drive speeds, combined with the Meade Smart Drive on both telescope axes, permit observatory-level precision in tracking, guiding, and slewing. Photo-guide speeds are selectable from 0.01x to 1.0x sidereal, in increments of 0.01x; fast-slew speeds are selectable from 1°/sec. to 8°/sec. in 0.1°/sec. increments. Use the 8°/sec. speed for rapid motion of the telescope across the skies; once near the target, switch instantly to a speed of 1.5°/sec. or 3°/sec. for centering in the viewfinder. Observing in the main telescope, use the 16x or 64x sidereal speed to place the object in the center of the field. Computer Optimized Internal Baffling: Unlike traditional Schmidt-Cassegrain designs, the primary mirror moves along a baffle tube in order to achieve focus, Meade's LX400 primary mirror is mounted independent of the baffle tube. This allowed Meade's engineers to take full advantage of the baffle design to create full stray light cut-off performance, in order to produce the maximum contrast. Additionally the secondary baffle, machined of aluminum with its distinctive outer knife-edges further minimizes stray light in the optical path. Focus Position Presets: By setting up to 9 focus positions, LX400 owners can customize perfect focus from observer to observer with different eyesight (similar to the custom settings in luxury cars to change the mirror, seat, and steering wheel settings from one driver to another). The feature is also very useful when using switching to various eyepiece and Barlow lens combinations or from a visual setup to a camera setup. UHTC Coatings: Standard on all LX400 telescopes, the importance of Meade's proprietary UHTC group becomes apparent when comparing total telescope light transmission, or throughput, caused by the multiplier, or compounding, effect of the four optical surfaces. With each optical surface contributing significantly to telescope light throughput, the effect of all four surfaces combined is indeed dramatic. At the H-a wavelength of 656nm., total transmission increases from 76.7% to 88.5%, an increase of 15.4%; at the helium wavelengths of 588nm. and 469nm. - strong emission lines in hot planetary nebulae - total telescope transmission increases by 13.8% and 16.8%, respectively; at the two nitrogen II lines of 655nm. and 658nm. and at the sulfur II line of 673nm., transmission is increased by 16%. Averaged over the entire visible spectrum (450nm. to 700nm.), total light transmission to the telescope focus increases by about 15%. More Info about UHTC Smart Mount: Revolutionary Smart Mount technology is standard equipment on all LX400 telescopes. Smart Mount improves the pointing accuracy of your LX400's telescope's "Go To" system with the following features: • Constantly improved pointing accuracy with every object centered and sync'ed. • Works with both equatorial and altazimuth configurations. • Simple routine to refine pointing accuracy for the entire sky with your equipment configuration and alignment. • Refined pointing data can be saved and reused for permanent and portable setups. Altazimuth and Equatorial Operation: For all visual observing applications, for lunar and planetary photography, and for many CCD imaging applications, Meade LX400 may be set up in the altazimuth mode - just attach the telescope's drive base directly to the tripod, use the GPS alignment procedure, and the telescope's computer actuates 2-axis tracking that keeps objects precisely centered in the field, even at high powers, during the entire observing session. For long-exposure astrophotography altazimuth-induced field rotation requires the new Ultrawedge or the #1220 (for 10", 12", 14", and 14" models) Field De-rotater, either of which may be purchased separately.

Additional Information

Name Meade - 20" LX400-ACF (f/8) Advanced Coma-Free OTA
Manufacturer Meade
Model 2006-40-00