PREORDER NOW!!!For the casual or beginning observer the Meade ETX-90AT may be all the telescope ever required. Or, for the advanced astronomer
who already owns a larger instrument, the ETX-90AT is the perfect ultraportable, diffraction-limited field telescope. Observe the
continually changing cloud-belt patterns on the surface of the planet Jupiter; shadows cast on to Jupiter as one of its four
principal satellites transits the planet's disc; the magnificent ring system and satellites of Saturn as well as dusky markings
and the ring-shadow on the surface of Saturn; Moon craters by the hundred, plus lunar rilles, mountain ranges, and fault lines,
all visible in brilliant, high-resolution, high-contrast detail; the variable phases of the planets Mercury and Venus; prominent
features on the surface of Mars. In deep-space the motivated observer will find it difficult to exhaust the quantity of visible
phenomena: the incandescent filamentary structure of the Orion Nebula; the elliptical luminosity of the Andromeda Galaxy with its
brilliant nucleus; the shining orb of the Hercules globular cluster with many of its outermost stars resolvable. These are only a
few of the literally thousands of celestial objects within the view of the Meade ETX -90AT telescope. Star catalogs list
innumerable double and multiple star systems, variable stars, open star clusters, globular clusters, diffuse nebulosities,
planetary nebulae, and spiral galaxies within the grasp of the instrument. The optional Autostar Computer Controller can locate
all of these objects automatically, in seconds.#497 Autostar Computer Controller
One of the most important advances in telescope control in the past 25 years, the Meade #497 Autostar Computer Controller turns
the ETX-90AT, ETX-105AT, or ETX-125AT into an automatic celestial object locating system. Just plug the Autostar into the
telescope's HBX port, do a quick (less than one minute!) telescope alignment, and you're ready to observe any object in the
Autostar's 30,000-object database.Best of all, the Meade Autostar is easy to use. Even the most novice observer will find himself
or herself locating dozens of fascinating celestial objects the very first night out - from commonly-observed objects such as the
rings of Saturn, the satellites of Jupiter, and the Orion Nebula (M42); to more difficult objects such as the Ring Nebula (M57) in
Lyra, the Spiral Galaxy (M33) in Triangulum, and the Sombrero Galaxy (M104) in Virgo; to very obscure objects near the telescope's
threshold of visibility such as the diffuse nebula NGC 6559 in Sagittarius, the galactic star cluster NGC 1778 in Auriga, and the
spiral galaxy NGC 3310 in Ursa Major.
The #497 Autostar Computer Controller is included as standard equipment with ETX-90AT, ETX-105AT, and ETX-125AT Astro
Telescopes.
Any of Autostar's database objects can be called up and entered on the hand controller display in seconds. The observer then
simply presses the GO TO pushbutton and watches as the telescope automatically slews (moves) to the object and places it in the
field of view. The effect of Autostar is to bring objects easily within reach which were previously unreachable for all but the
most dedicated of amateur astronomers.
Includes:
* Maksutov-Cassegrain optical tube assembly (D=90mm, F=1250mm, f/13.8) with EMC super multi-coatings;
* Internal flip-mirror system for either straight-though or 90 degree observing position;
* Fork mount with electric slow-motion controls, setting circles and locks on both axes;
* Electronic control panel;
* 9 (from 2x sidereal to 5 degree/sec) dual-axis motor drive system with #497 Autostar controller;
* Sidereal-rate tracking in equatorial mode with optional table tripod or deluxe field tripod;
* Internal battery compartment accepting eight (user-supplied) AA-size batteries;
* 8 x 21mm erect-image viewfinder;
* Series 4000 Super Plossl 26mm eyepiece (1.25");
* #497 Autostar Hand Controller
* #884 Deluxe Field Tripod
* Operating instructions.
* 15" x 7.3" x 8.5"
* Telescope Net Weight: 9.2 lbs.
* Telescope Shipping Weight: 12.4 lbs.
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An important optional feature to optimize the performance of your Meade telescope.
Image brightness in a telescope is crucially dependent on the reflectivity of the telescope's mirrors and on
the transmission of its lenses. Neither of these processes, mirror-reflectivity or lens-transmission, is,
however, perfect; light loss occurs in each instance where light is reflected or transmitted. Uncoated glass,
for example, reflects about 4% of the light impacting it; in the case of an uncoated lens 4% of the light is
lost at entrance to and at exit from the lens, for a total light loss of about 8%. |
Early reflecting telescopes of the 1700's and 1800's suffered greatly from mirrors of poor reflectivity- reflection losses of 50%
or more were not uncommon. Later, silvered mirrors improved reflectivity, but at high cost and with poor durability. Modern
optical coatings have succeeded in reducing mirror-reflection and lens-transmission losses to acceptable levels at reasonable
cost.
Meade Standard Coatings: The optical surfaces of all Meade telescopes include high-grade optical coatings fully consistent in
quality with the precision of the optical surfaces themselves. These standard-equipment coatings include mirror surfaces of highly
purified aluminum, vacuum-deposited at high temperature and overcoated with silicon monoxide (SiO), and correcting lenses coated
on both sides for high light transmission with magnesium fluoride (MgF2). Meade standard mirror and lens coatings equal or exceed
the reflectivity and transmission, respectively, of virtually any optical coatings currently offered in the commercial telescope
industry.
The Meade UHTC Group: Technologies recently developed at the Meade Irvine coatings facility, however, including installation of
some of the largest and most advanced vacuum coating instrumentation currently available, have permitted the vacuum-deposition of
a series of exotic optical coatings precisely tuned to optimize the visual, photographic, and CCD imaging performance of Meade
telescopes. These specialized, and extremely advantageous, coatings are offered here as the Meade Ultra-High Transmission Coatings
(UHTC) group, a coatings group available optionally on many Meade telescope models.
In Meade catadioptric, or mirror-lens, telescopes (including the ETX-90EC, ETX-105EC and ETX-125EC; LX10, LX90, and LX200GPS
Schmidt-Cassegrains; and LXD55-Series Schmidt-Newtonians) before incoming light is brought to a focus, it passes through, or is
reflected by, four optical surfaces: the front surface of the correcting lens, the rear surface of the correcting lens, the
primary mirror, and the secondary mirror. Each of these four surfaces results in some loss of light, with the level of loss being
dependent on the chemistry of each surface's optical coatings and on the wavelength of light. (Standard aluminum mirror coatings,
for example, typically have their highest reflectivity in the yellow region of the visual spectrum, at a wavelength of about
580nm.)
Mirror Coatings: Meade ETX, Schmidt-Cassegrain, and Schmidt-Newtonian telescopes equipped with the Ultra-High Transmission
Coatings group include primary and secondary mirrors coated with aluminum enhanced with a complex stack of multi-layer coatings of
titanium dioxide (TiO2) and silicon dioxide (SiO2). The thickness of each coating layer precisely controlled to within +/-1% of
optimal thickness. The result is a dramatic increase in mirror reflectivity across the entire visible spectrum; at the important
hydrogen-alpha wavelength of 656nm. - the predominant wavelength of emission nebulae - reflectivity is increased from 89% to over
97%.
Correcting Lens Coatings: Meade telescopes ordered with the UHTC group include, in addition, an exotic and tightly-controlled
series of coatings on both sides of the correcting lens or correcting plate, coatings which include multiple layers of aluminum
oxide (Al2O3), titanium dioxide (TiO2), and magnesium fluoride (MgF2). Per-surface light transmission of the correcting lens is
thereby increased at the yellow wavelength of 580nm., for example, to 99.8%, versus a per-surface transmission of 98.7% for the
standard coating.
The importance of the 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, as demonstrated by the graphs on the facing page,
as well as by the table of the brightest nebular emission lines. At the H-alpha wavelength of 656nm., total transmission increases
from 77% to 93%, an increase of 93/77 or 21% at all three nitrogen-III and sulfur-II wavelengths of 655nm. and 673nm.- prominent
lines in certain galactic nuclei and in supernova remnanats such as the Crab Nebula- transmission increases by 21%; ; at the
helium wavelengths of 588nm. and 469nm. - strong emission lines in hot planetary nebulae - total telescope transmission increases
by 18% and 19%, respectively; at the two nitrogen II lines of 655nm. and 658nm. and at the sulfur II line of 673nm., transmission
is increased by 21%. Averaged over the entire visible spectrum (450nm. to 700nm.), total light transmission to the telescope focus
increases by about 20%.
Observing with the UHTC: Meade ETX, Schmidt-Cassegrain, and Schmidt-Newtonian telescopes equipped with the UHTC present
dramatically enhanced detail on the full range of celestial objects - from emission and planetary nebulae such as M8, M20, and M57
to star clusters and galaxies such as M3, M13, and M101. Observations of the Moon and planets, since they are observed in
reflected (white) sunlight, benefit in image brightness from the full spectrum of increased transmission. The overall effect of
the UHTC is, as it relates to image brightness, to increase the telescope's effective aperture. Image brightness (i.e., the
ability to see faint detail) of the Meade 10" LX200GPS is, for example, effectively increased by about one full inch of aperture.
| Emission Line | Wavelength (nm.) | Transmission: Standard Coatings (%) | Transmission: UHTC Group
(%) | Increase* |
| Hydrogen-alpha (Ha) | 656 | 76.9 | 93.1 | 21% |
| Hydrogen-beta (Hb) | 486 | 75.3 | 85.8 | 14% |
| Oxygen III | 496 | 76.5 | 85.4 | 12% |
| Oxygen III | 501 | 77 | 85.4 | 11% |
| Helium II | 496 | 72.5 | 86.1 | 19% |
| Helium I | 588 | 79.5 | 93.5 | 18% |
| Nitrogen II | 655 | 77 | 93.2 | 21% |
| Nitrogen II | 658 | 76.7 | 92.8 | 21% |
| Sulfer II | 673 | 75.7 | 91.8 | 21% |
* The % increase is obtained by dividing the UHTC-transmission (column 4) by the standard coatings transmission
(column 3).
Effects on CCD Imaging: While the human eye loses sensitivity to light beyond wavelengths of about 700nm., CCD imaging chips
remain sensitive to about 750nm. and longer, wavelengths at which the reflectivity of an aluminum coating is near its lowpoint.
Importantly, however, the UHTC's total light transmission at 750nm. is 83%, vs. 72% for standard coatings, an increase of 83/72,
or 15%.
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