ETX-90 3.5" go-to Mak portable observatory, UHTC, tripod, case, and Autostar computer

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The fully go-to computerized ETX-90 Portable Observatory is designed to be the ideal ultra-portable telescope. It combines Meade’s unsurpassed optics with industry-leading electronics to deliver a truly exceptional viewing experience. The computer-optimized Maksutov-Cassegrain optics of the ETX-90 yield remarkable lunar, planetary, star cluster, and binary star images. Thanks to the cost efficiency of modern injection-molded components, these images cost far less than those of apochromatic refractors and competitive fork-mount Maksutovs of similar aperture.

The ETX-90’s standard equipment AutoStar computer hand control is amazingly simple to operate. It will even help you align the scope on the sky. You don't have to know Castor from Pollux, or Albireo from Zubeneschamali. All you have to do is tell the AutoStar where and when you are on Earth, level the tube, and show it where North is located. The AutoStar computer will do the rest.

The Meade ETX-90’s Optical System . . .

  • Maksutov-Cassegrain optical tube: 90mm (3.5") aperture, 1250mm focal length, f/13.8 focal ratio.

  • Fully multicoated optics: Anti-reflection UHTC (Ultra High Transmission Coatings) multicoatings on both sides of the Maksutov corrector lens, plus high light transmission enhanced aluminum multicoatings on the mirrors, provide a 16% increase in light throughput compared to standard coatings. UHTC multicoatings effectively add the equivalent of more than a quarter of an inch of extra light-gathering aperture to the performance of a scope with standard coatings, but at no increase in size or weight.

  • Excerpts from a review of the original ETX-90 optics: Sky & Telescope magazine said, "The optics in our test telescope were excellent . . . Familiar with how rarely 8-inch and larger telescopes experience moments of good seeing, I was pleasantly surprised by how often the atmosphere served up diffraction-limited conditions for the smaller aperture ETX-90. You don't see more detail with the small scope, but the sharp images are very satisfying and a frequent reminder of the excellent optical quality.
  •  
    "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 26mm (48x) eyepiece, I could easily see the rings' Cassini Division and several bands on the ball of the planet. Even at this modest magnification the moons Titan, Rhea, and Dione were clearly visible, and Tethys became evident when the power was increased to 156x.
    "The bottom line is that the ETX-90 showed me everything I could expect from an instrument of its size."

    While the ETX-90 Portable Observatory’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: Dust covers protect the meniscus corrector lens and seal the Cassegrain focus on the rear cell.

  • Finderscope: The supplied straight-through non-magnifying illuminated red dot finder seems to projects a red dot of light on the sky (not visible in the eyepiece) to show you where the scope is pointing at all times.

  • Star diagonal: Built-in first surface flip-mirror. For astronomical observing, the internal flip-mirror directs the image to 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° viewing angle image-erecting diagonal for upright and right-reading terrestrial viewing.

  • Two eyepieces: One is a 1.25" 26mm Series 4000 Super Plössl (48x). The eyepiece field of view is 1.04 degrees, more than twice the diameter of the full moon. The second eyepiece is a higher power 1.25" 9.7mm Super Plössl (129x) for close-up lunar, planetary, binary star, and globular star cluster views.

The Meade ETX-90 Portable Observatory Telescope’s Mechanics and Electronics . . .

  • Dual fork arm altazimuth mount: The optical tube is aluminum. The rear cell, fork arms, and drive base are durable metal-reinforced injection-molded plastic that helps keep the cost of the ETX-90 so very reasonable. While the molded parts of the ETX-90 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 ETX-90 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 for tracking objects under the control of the supplied AutoStar computer. The motors are powered for up to 20 hours by six AA batteries (not supplied) in a battery holder that fits into an internal battery compartment in the telescope base. An optional #546 AC adapter can power the scope from household AC. The #546 adapter has a clip that connects to the 9V connection in the battery compartment that normally attaches to the battery holder. The battery holder must be unclipped from the scope in order to use the #546.
  • When used in the default altazimuth mode, the supplied AutoStar computer hand control moves the scope in any of four directions (right/left and 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 tracking objects. No manual slow motion controls are provided – or needed, as pushbuttons on the AutoStar hand control will do all the powered slewing and centering you might want. When set up on the supplied tripod for equatorial (polar) operation using the tripod’s built-in equatorial wedge, 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.

  • 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. 
  •  
    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 26mm eyepiece"

  • AutoStar computer operation: The operation of the ETX-90 Portable Observatory is simplicity itself. On-screen operation instructions guide you through setup and use of the AutoStar and a help function is only a keystroke away. Once you mount the scope on its tripod, aim the scope north and level the optical tube. Enter your observing location’s latitude and longitude into the AutoStar computer hand control. This needs only to be done once, as the scope will keep the location in its memory, as well as that of several other favorite observing sites that you can call up at will. Enter the time. The ETX-90 Portable Observatory will orient itself to the sky and quickly slew to the first of two alignment stars. If that star is not precisely centered, a touch or two on the AutoStar hand control directional push buttons quickly centers it. Do the same with the second alignment star the scope moves to and you’re ready to observe. That's it! 
  • It takes only a few minutes to begin observing. For the rest of the evening, a computer in the AutoStar controls the scope’s altitude and azimuth motors to keep you precisely centered on whatever you aim at, for as long as you want to observe.

  • Adjustable height tripod and tripod carry bag: The supplied full-length field tripod provides a rigid mounting platform for virtually any observing application, astronomical or terrestrial, and can be used for either standing or seated observing. The tripod has tubular 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 a little 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. The tripod comes with a soft carrying case.

  • Hard case for scope: A locking hard case with carry handle is provided to transport and protect the ETX-90.

  • AutoStar Software Suite: This extensive software package is included as standard equipment with the ETX-90 Portable Observatory. It is designed to integrate the telescope with your PC or laptop computer for an enhanced range of performance features. The AutoStar Software Suite includes a planetarium program with a database of 19,000,000 stars and deep space objects for display on your computer screen. It includes all the standard planetarium program features for stand-alone use when nights are cloudy.
  •  
    In addition, if you connect the scope to your computer (using the supplied cable), the program lets you click on objects in the sky map 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. 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. You can use it to control your telescope remotely via the Internet. “Talking Telescope" software (included) converts AutoStar text displays to synthesized speech 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 over the internet from Meade’s website.
Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
186x
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

11.7
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

1250mm
Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

f/13.8
Resolution:
This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.3 arc seconds
Aperture:
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
3.5"
Weight:
The weight of this product.
22.4 lbs
Heaviest Single Component:
The weight of the heaviest component in this package.
13.3 lbs
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
Maksutov-Cassegrain
 
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Yes
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Great
Planetary Observation:
Good
Binary and Star Cluster Observation:
Good
Galaxy and Nebula Observation:
Fair
Photography:
Yes
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Yes
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Yes
Planetary Photography:
No
Star Cluster / Nebula / Galaxy Photography:
No
Warranty:
1 year
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1. Jason on 5/15/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I purchased the etx125 version of this scope almost 3 years ago and this has been one of the most versitile grab and go scopes I have used. I can set this up and have it aligned in about 5 min. The tracking is fairly accurate and the go-to features are spot on.
The down side to a scope this size is the lack of light capturing ability with only a 5in collector and its ability to get truly clear images of deep sky objects, however this scope is a real gem when looking at planitary objects. I have been able to see some spectacular lunar and planitary shots with this scope and produces a much better image than my 10" dob. I would highly recommend purchasing the auto focuser from Jim's Telescope co(JMI)as this makes it much easier to use when looking at something directly overhead. Overall for making quick runs to the viewing spot you can't beat this little scope.
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2. DANIEL on 5/1/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Dear astronomics,

The easiest way for me to review your company is to say I have searched the internet and Astronomics offers great service, affordable prices and speedy delivery. I have been an amateur astronomer since I was ten years old (I am now 62).

As I got older I wanted to share my knowledge with my grandchildren, nieces, nephews,friends and the families who often are drawn to the excitement. so as often as I can I set up my scope and the kids are drawn to it like a magnet. Recently the purchase of a solar lens and camera from astronomics allowed me to open a whole new realm of astronomy to these kids. Nothing beats the amazement in their eyes and the good feeling to know that myself and astronomics have renewed the interest in astronomy in these new fresh intellects. If I had an I-Pad I could begin filming some of the amazing views for the kids who can't be available when I have a "scope party" Day or night.

I look forward to upgrading from my Meade ETX 125.to a larger scope and you can be assured Astronomics will be my only choice to purchase a new scope to open even deeper views of our beautiful universe and keep the interest going in these kids.

Thank you for helping me help others,
Daniel Driscoll
1628 Holly Parkway
Williamstown NJ 08094

E-mail: DD734@AOL.COM
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General Accessories
Drive Motors and Drive Accessories (1)
#546 AC Adapter for Meade ETX-60/70/90
by Meade
Quantity:  
$29.95 
  • 90mm f/13.8 Maksutov-Cassegrain optics; UHTC (Ultra High Transmission Coatings) multicoated optics
  • Dual arm fork altazimuth mount with nylon right ascension and declination bearings
  • Electric slow motion controls and locks on both axes
  • Setting circles (3.5" diameter declination, 7" undriven right ascension)
  • On/off switch, 12v input, auxiliary outputs, and computer hand control input in drive base
  • Sidereal rate DC servo-motor drive powered by 6 user-supplied AA batteries
  • Non-magnifying red dot finder
  • 1.25" 26mm Super Plössl eyepiece (48x)
  • 1.25" 9mm Super Plössl eyepiece (129x)
  • Built-in flip-mirror diagonal
  • Dust covers for optical tube
  • Field tripod with built-in equatorial wedge and soft carry bag
  • Hard case for scope
  • AutoStar computer hand control with built-in database of more than 30,000 stars and objects
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Meade - ETX-90 3.5" go-to Mak portable observatory, UHTC, tripod, case, and Autostar computer

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Meade - ETX-90 3.5" go-to Mak portable observatory, UHTC, tripod, case, and Autostar computer
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Our Product #: ETX90PAK
Manufacturer Product #: 3514-04-20
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The fully go-to computerized ETX-90 portable observatory has computer-optimized UHTC multicoated 90mm Maksutov-Cassegrain optics, AutoStar computer control, tripod, tripod carry bag, scope hard case, and two eyepieces – all at a remarkably sensible price . . .





. . . our 34th year