|
Meade - 8 inch LXD75 SN-8AT with UHTC with 3 Year Sky Assurance
|
$ 1288.99
Reg.$ 1798.99
SAVE $ 510.00 | |
| 0804-75-02_SKY
 |
|
Click here for recommended accessories |
|
|
Premium Meade® LXD75 Optics
Diffraction-Limited Optics
Meade’s Schmidt-Newtonian and Schmidt-Cassegrain optics yield pinpoint stellar images over an
extremely wide field-of-view with only half the coma of standard Newtonians of the same focal
ratio. Optical Tube Construction
Schmidt-Newtonian and Schmidt-Cassegrain optics are mounted in precision-machined aluminum cells,
which are then mounted in sturdy steel tubes that are baked with high-grade textured enamel paint.
The optical tube assembly is closed, reducing air currents inside the tube. This prevents
distortion of an otherwise sharp image. Plus, a closed tube significantly helps keep the optics
clean.
Corrector Lens
Fully corrects for spherical aberration and provides pinpoint star images. Water-white glass is
used in all Schmidt-Newtonian and Schmidt-Cassegrain corrector lenses to maximize light
transmission. The use of water-white glass increases light transmission by more than 10%, as
compared to competitive telescopes using soda-lime glass.
Individually Figured Optics
Schmidt-Newtonian and Schmidt-Cassegrain corrector lenses and mirrors are individually figured to
create a superior optical system that is renowned for its exquisite smoothness and performance.
Pyrex® Primary Mirror
Premium-grade Pyrex mirrors are used in all Schmidt -Newtonian and Schmidt-Cassegrain optical
systems, providing exceptional thermal stability versus competing models using standard plate
glass.
System Highlights
* Sturdy Mount with Heavy-Duty Castings: Designed by Meade’s engineers and manufactured for
high-performance observing and astrophotography.
* Shaft & Bearing System: The sturdy German Equatorial Mount is accurate and precise. The RA
and Dec axes move effortlessly on four high-precision stainless steel ball bearings.
* High-Precision Worm Gears: Located on both axes for smooth tracking and slewing.
* High-Precision Pointing (HPP): For even more-precise pointing, use the HPP function. HPP
puts objects in the center of the field-of-view, which allows you to confirm deep-sky objects at
the faintest limits of the telescope’s capability.
* Periodic Error Correction: Corrects periodic errors on the RA axis over the course of one
or more training periods, thereby minimizing guiding corrections during long-exposure
photography.
* 9-Speed Drive Controls: From a rapid slew rate of 4.5°/sec. to 1x sidereal – it’s all
controlled from the Autostar controller.
* 3-Star Alignment: Ensures precise alignment while eliminating the need for a complicated
optical/mechanical alignment process.
* Heavy-Duty Tripod: Variable-height field tripod with spreader bar brace provides the
stability and vibration damping required for visual observation and astrophotography.
* Illuminated Polar Alignment Viewfinder: For quick, precise polar alignment.
* Power Supply: Powered by 8 D-size batteries. Can also be powered by optional car cigarette
lighter or AC wall adapter.
* Enhancements
New Optical Tube Assemblies
The LXD75 Schmidt-Newtonians are supplied with an upgraded 8x50 viewfinder, and the standard
precision all-metal 1.25”/2” O.D . rack & pinion focuser.
Stable Meade LXD75 German Equatorial Mount
Designed for high-performance observing and astrophotography, the LXD75 Series sets a new Meade
standard in their price class for sturdiness, precision operation and smoothness of movement.
With the LXD75, Meade engineers have created a virtually backlash-free equatorial mount
incorporating heavy-duty castings and four high-precision stainless steel ball bearings in both
RA and Dec axes.
New Design LXD75 Drive System
The reliable LXD75 drive system has enhanced precision alignment of the motor gear assembly for
greatly reduced backlash and tracking smoothness.
New Design Heavy-Duty Tripod
The new, heavy-duty, all-metal field tripod utilizes a locking spreader bar (with three 1.25”
eyepiece holders) to lock each leg in place, virtually eliminating flexure. Each leg has two
anodized aluminum leg extension locks with an internal brake to eliminate slipping of the
internal extending leg. These locks are inward facing so that no accidental bumping of the leg
locks can occur.
Features:
* Autostar Suite
* Available with either: Standard or UHTC (Ultra-High Transmission Coatings Group)
* 2” Focuser: Aluminum rack and pinion focuser allows the user to achieve a precise focus.
* Eyepiece Holder: Accepts both 1.25” & 2” eyepieces. Allows use of all common telescope
accessories and cameras.
* 8x50 Achromatic Viewfinder: Easily locate and center deep-sky objects.
* Made in the U.S.A. and Performance Tested: All Meade Schmidt-Newtonian and Schmidt
-Cassegrain optics are manufactured at Meade’s state-of-the-art facility in Irvine, Calif., then
performance tested on an Interferometer
|
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 (Hß) | 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%.
|
