Meade Ultra High Transmission Coatings (UHTC) Group
An important optional feature to optimize the performance of your Meade telescope. What is it and is it worth it?
As you may have noticed you have a choice to make when buying many of the popular Meade telescopes. Standard Coatings or UHTC Coatings. The price difference on the same telescope can be between 50 and 350 dollars more for UHTC Coatings depending on the model telescope. Is it really worth it? YES! Our sales history shows UHTC outsells the Standard Coatings models about 20:1. Is this a sales pitch? Yes it is. We want you to purchase the UHTC Coatings option - we want you to see as much as possible - we want you to get the most from your new telescope. If you have read our article, " How To Select Your First Telescope" or are a seasoned amateur astronomer, you know that the function of a telescope is to gather light. Telescopes have lenses and or mirrors that cause the telescope to naturally loose light through reflectivity and transmission. Better lens coatings make a difference - a noticeable difference. For visual observation, objects such as star clusters will be brighter and show more detail. Deep space nebule are already faint in telescopes, your UHTC coated telescope will allow you to see them better. Planetary detail on Jupiter will yield a higher contrast image and more red details. A simple Google search for "Meade UHTC Coatings" and you can read many users who praise the UHTC group as a "no brainer".
If you have any thought of doing astrophotography with your new Meade telescope, the UHTC again will make a substantial difference. More detail with less exposure time. Better resolution and higher contrast.
You can read technical babble about UHTC (dont worry, we provided it below). You can read about nanometers and emission line information for % increase on each - if you want (yes, its all down below) but to keep it simple, Meade telescopes with UHTC perform better. UHTC Coatings is equivalent to adding 1/4 to 1 inch of aperture depending on the size of the telescope. For example, image brightness of the 10 inch LX200 GPS effectively increased by about 0.75 inch of aperture.
Here is some more information on UHTC Coatings for your reading pleasure.
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 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.
|Each time light encounters a mirror (above) or lens (below) surface, some light is lost. In the case of a lens, light is lost both at entrance to and at exit from the lens.|
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, or virtually any optical coatings currently offered in the commercial telescope industry.
The Meade UHTC Group: Technologies recently developed at Meade Irvine coatings facility, however, including installation of some of the largest 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 performace 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 ETX90, ETX105, and ETX125; LXD75, LX90, LX200, LX200R and RCX400) before incoming light is broght 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.
Mirror Coatings: Meade ETX, Schmidt-Cassegrain, and Schmidt-Newtonian telescopes equipped with the Ultra-High Transmission Coatings group include primary and secondary mirros coated with aluminum enhanced with a complex stack of multi-layer coatings of titanium dioxide (TiO2) and silicon dioxide (Si02). The thickness of each coating layer is precisely controlled to within 1% of optimal thickness. The result is a dramatic increase in mirror reflectivity across the entire visible spectrum.
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 (AI2O3), titanium dioxide (TiO2), and magnesium fluoride (MgF2). Per-serface 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. At the H-a wavelengh of 656nm, total transmission increases from 76.7% to 88.5%, an increase of 15.4%. At the helium wavelengths of 588nm. and 469nm - stron emission lines in hot planetary nebule - 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 visuble spectrum (450nm to 700nm) total light transmission to the telescope focus increased by about 15%.
Observing with the UHTC Coatings: Meade ETX, Schmidt-Cassegrain, and Schmidt-Newtonian telescopes equipped with the UHTC present dramatically brighter images 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.
|Emission Line||Wavelength (nm)||Transmission: Standard Coatings (%)||Transmission UHTC Group (%)||Increase|
The overall effect of the UHTC is, as it relates to image brightness, to increase the telescope's effective aperture. Image brighness of the Meade 10" LX200GPS is, for example, effectively increased by about 0.75 inch of aperture.
Ordering the UHTC Coatings: The Meade Ultra-High Transmission Coatings group, if desired, must be specified at the time of telescope purchase. The UHTC Coatings can not be retrofitted. The UHTC Coatings are available for many Meade telescopes such as the Meade ETX, LX90GPS, LX200 GPS, LX200R GPS, and RCX400.