Universe Today

Are you curious about telescope optics? Then you've come to the right place. Telescope optics doesn't necessarily mean the physical lenses and mirrors that comprise the instrument, but the behavior and properties of light coming into them! Are you ready to learn more? Then let's go….

Telescope Optics – The Refractor Telescope: In a simple telescope optics world, the refractor telescope consists of a single objective lens and eyepiece lens. These sets of convex lenses, which cause incoming parallel light rays to converge, produce a virtual image one focal length from the lens, on the same side of the lens that the parallel rays are approaching on. Add another converging lens and the result is magnification. This process also causes diffraction – where interference in the incoming light waves is easily observed. Diffraction reduces the instrument's ability to resolve differentiating light sources. The refractor telescope optic design also causes dispersion – a scattering of the incoming light waves.

Telescope Optics – The Reflector Telescope: When it comes to reflections, there are two types:specular reflection and diffuse reflection. In the case of telescope optics, the reflection of starlight is specular. When gathering light, the direction of the reflected ray is determined by the angle the incident ray. For example, if the incoming starlight should hit a flat plane, it would be redirected in exactly the same manner in the way it came. However, a curved mirror can produce a magnified image! For telescope optics to work in a reflector, the primary mirror surface is parabolic – redirecting the collected incoming light rays back to a focal point. It is here that specular reflection comes into play again – for the next focal point is a flat mirror called a secondary The light rays are then redirected back to a simple set of lens – the eyepiece – which work on the same principle as the refractor and produce magnification.

Telescope Optics – The Telescope Eyepiece: All telescope optics share a common end factor – the eyepiece. In itself, the telescope eyepiece acts like a miniature refractor telescope. It consists of a variety of interior lens designs – from simple to very complex. Each set of interior lenses refracts the incoming light to produce a virtual image. The shape of these lenses, concave, convex, planoconcave, etc. determine the amount of "field" which can be observed as final result at a focal point located just outside the final lens. The telescope eyepiece can also produce optical effects such as interior reflections and dispersion, resulting in multiple images and unwanted colors.

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Would you like to learn more about how a telescope comes to focus? What exactly is a telescope focuser? How does a telescope focuser work? What different types of telescope focusers are there? Are some types of telescope focusers better than others for certain applications? If you have questions, then you've come to the right place! While all telescopes are equipped with an exterior knob-controlled focuser (the interior workings are referred to as a telescope draw tube), not all are exactly alike. Let's take a brief look at the telescope focuser, what it is and what it does…

Telescope Focuser: Rack and Pinion Focuser – The most common telescope focuser of all is the rack and pinion focuser. It gets its name from the rack of small gear teeth which run along the spine of the drawtube which move it in and out using pinion gears connected to the focus knob. This "in and out" motion is what brings the eyepiece to the focal point. As we know, different eyepieces have different focal points, so there's definitely a need for traveling distance! A well-built rack and pinion focuser will last the lifetime of the telescope, but some applications require an even finer focus than ordinary focusers will allow – like planetary viewing and astrophotography. This is where the Telescope Microfocuser comes into action. Using the same principle as the rack and pinion, the microfocuser has an additional set of even smaller teeth on the rack to allow even for finer adjustment. These systems don't replace the standard coarse focus, just simply add another alternative.

Telescope Focuser: Crayford Focuser – Some telescopes use a system called the Crayford focuser. Unlike the rack and pinion, the Crayford is a totally different design that doesn't use gears to move the drawtube – it works on roller bearings! The tube is moved by a roller and is carried along by user adjustable pressure bearings. The system was meant to eliminate backlash that can sometimes be found in inferior rack and pinion models. Like the microfocuser, the Crayford also has two "speeds" – one for coarse adjustment and the other for fine focus. Designed for both Schmidt Cassegrain styles and reflectors/refractors these superior design focusers run the gambit on versatility. Able to be controlled digitally, sense and account for temperature differences, carry unbelievable weight loads and even focus right down in the "nano" level.

Telescope Focuser: Helical Focuser – A helical focuser works on a rotating principle much like the focusing mechanism for a camera lens. The focuser is threaded to provide the rotary motion which then converts to linear motion. This means you just twist the focuser and the eyepiece moves up and down. While this design is simple, it is not always convenient, because when accessories (such as a diagonal) are attached to the eyepiece, they will also rotate as the telescope is focused.

Telescope Focuser: Electric and Motorized Telescope Focusers – This brings us right into the Electric Focusers and Motorized Telescope Focusers category. Now we're talking technical… and we're also talking about add-on equipment that can virutally eliminate vibration caused by touching the focuser knob. Of course, these are also variable speeds and can include hand-controllers… But bear in mind they are not the whole focusing system! Rather than physical move the focuser via a knob, electric and motorized focusers use a keypad that adjust the focus incrementally with variable speeds that are user defined.

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Refractor, reflector, Schmidt Cassegrain, radio telescope and more… They are all telescopes, but how does a telescope work? Let's find out…

How Does A Telescope Work – The Electromagnetic Spectrum: First and foremost we need to begin our discussion on how a telescope works by learning about exactly what a telescope collects – the electromagnetic spectrum. We often believe that a telescope can only study light waves, but there's far more there than meets the eye. The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation: radio, microwave through far infrared, near infrared, visible, ultra-violet, x-rays, gamma rays and high energy gamma rays. The behavior of the electromagnetic spectrum depends on its wavelength and telescopes are designed to pick up on certain wavelengths. The light we see with our eyes is really a very small portion of the electromagnetic spectrum! Electromagnetic radiation with a wavelength between 380 nm and 760 nm (790–400 terahertz) is detected by the human eye and perceived as visible light. Even though infrared and ultraviolet are also called "light" their wavelength is just outside human perception.

How Does A Telescope Work – Collecting The Waves: How does a telescope work? By collecting the incoming waves of the electromagnetic spectrum. Remember, a telescope does not have to collect visible light to be considered a telescope! Most telescope's primary collection surfaces are parabolic, because the nature of the shape amplifies the wave by directing it back to a focal point. Paraboloid reflectors can be commonly observed throughout much of the world in microwave and satellite dish antennas – and one need not look any closer than the primary mirror of a reflector telescope to see another parabola! Once the incoming waves have been refectled to a focal point, they are then gathered for study. In the case of radio equipment, this is the feed horn which then amplifies the focalized radio waves for study. For a telescope, the light waves at the focal point are then amplified again by the telescope eyepiece. Like the parabola bending the light waves, a lensed refractor telescope bends incoming light rays to a focal point as well. Gamma rays, X-rays, infrared and ultra violet… They are all collected with a stylized sensor and returned to be amplified and studied.

How Does A Telescope Work – Concentrate and Study: Once the the electromagnetic spectrum is gathered and sent to a focal point, it's time to study! For frequencies we cannot see, the collection device send the information back in various forms where it is then analyzed by a computer program. In an optical telescope, visible light waves are further magnified by telescope optics called the the eyepiece where they are examined by the human eye. Almost as soon as the photographic process was discovered, it was turned towards collecting photons. Astronomers quickly caught on to using photography as a research tool and today's modern charge coupled devices – CCD – combined with adaptive optics can reveal extremely faint details with a clarity that nearly rivals a space telescope!

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The Meade ETX-80 Telescope is one of the most popular beginner telescopes of all time. For the beginning or intermediate observer the Meade Autostar "Go To" controller and motorized mount supplied with the ETX 80 is a revelation that permits the observation of hundreds of objects the very first clear night out. Thanks to its wide-ranging capabilities, the ETX 89 equipped with Autostar is also a respected tool in the arsenal of an experienced observer as well. Let's take a look at its features…

ETX 80 – Set Up and Alignment: The Meade ETX-80 has a simple and straightforward set up procedure. The tripod comes with a level and it is easy to adjust the height for user comfort. Next you simply attach the motorized alt-az mount and insert the optical tube. Once ready, it's time to use the Autostar computer telescope system and do an alignment process. A provided compass will also help you to find north! Just enter the date, time and location into the keypad and the telescope will then slew to a bright star. Align the star in the center of the eyepiece and press enter. After your choice of alignment procedures, your ETX 89 telescope will be ready to take you on a tour of the universe.

ETX 80 – Touring the Night Sky: The ETX 80 computer system with integrated, factory-calibrated time chip, permits the automatic location of over 1400 celestial objects. Just enter the object you wish to observe onto the AutoStar display, and press GO TO. Autostar's celestial object database includes more than 1400 astronomical objects, any of which may be entered on to the Autostar display; alternately, the Right Ascension and Declination of any object in the sky may be input to the Autostar display. In either case when the observer presses GO TO, the telescope automatically moves to the object at 4.5°/sec. on both telescope axes, and places the object in the telescopic field of view. Autostar's database for Meade DS-2000 telescopes includes the following celestial objects: 66 named objects (e.g., the Orion Nebula), 74 galaxies, 31 diffuse nebulae, 19 planetary nebulae, 135 star clusters, 109 objects from the Caldwell Catalog of the best objects for small telescopes, 110 Messier (M) objects; the complete Messier catalog, 943 stars from the Smithsonian Astrophysical Observatory (SAO) catalog, including 395 double stars, 189 variable stars, and other stars of special note, 50 Earth-orbiting satellites, 26 asteroids, including all of the brightest asteroids, 15 periodic comets, 8 major planets, from Mercury to Pluto for 1586 objects, total. However, the user must remember that you are working with an 80mm light gathering source and the huge database just isn't possible in optics not much larger than average binoculars. Do not be discouraged, however… For a great many of these objects can be seen and you will soon learn the limitations of your telescope and your skies.

ETX 80 – Telescope Mechanics and Extras: The Meade ETX-80 comes equipped with a 9.7mm and 26mm Plossl eyepiece, a built-in Barlow lens (which doubles the power the eyepiece), a compass and an erecting prism for terrestrial use. The computer control panel of the AutoStar features an auxiliary input port and on/off LED, a built-in timer and a reminder alarm for use with astrophotography applications. The controller also features Digital Readouts of telescope position, continuously in Right Ascension and Declination with precise sidereal-rate tracking. Once and object is located the mount will track it automatically on both telescope axes, simultaneously, keeping it centered in the eyepiece field. You can also choose to manually use pushbuttons to move the telescope on either or both axes, simultaneously, at any of nine drive speeds, from very slow 2x sidereal to fast 4.5°/second.

The ETX 80 offers a fairly fast focal ratio of f/5 at a 400mm (15.75") focal length for pleasing, wide field views. The optical tube dimensions are 3.6" dia x 14.5" and it can deliver up to 275X in practical magnification. The ETX 80 telescope requires six AA batteries to operate which hold an expected life of about 20 hours. The battery compartment is internal to prevent cordwrap and is also AC adaptable and capable of using a car battery adapter. When cared for properly, this is an excellent travel scope, outreach tool and first telescope for more advanced users.

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Are you curious about reflecting telescopes? A reflecting telescope is any telescope that uses a mirror as its primary light gathering source. The body of the telescope may be a solid tube, or it may be fashioned from truss tubes to hold the secondary mirror at the right distance. A reflecting telescope can also be combined with lenses to form a hybrid! Let's take a general look at each style…

Reflecting Telescope – The Newtonian Reflector: This type of reflecting telescope is named after its inventor, Sir Isaac Newton, and it is the most commonly used of all. Sometimes called a Newtonian telescope, it consists of a simple parabolic mirror which redirects the incoming light to a focal point on a secondary mirror. The telescope eyepiece is then aimed at the secondary mirror, much like a microscope, to magnify the image. This simplistic design is free of chromatic aberration and offers a shorter focal ratio – allowing for much wider apparent fields of view. The reflecting telescope by nature is far less expensive to produce with less surfaces to grind – making it "affordable aperture".

Reflecting Telescope – The Truss Tube Reflector: This type of reflecting telescope works on exactly the same principle as the Newtonian reflector, but instead of using a solid telescope tube as a body, a truss tube assembly holds the secondary mirror at the proper distant to achieve a focal point. The advantage to this design is that very large telescopes can be dis-assembled for easier transport. A special fabric shield, called a light shroud, can be stretched over the framework to help keep out stray light and protect the mirror surface from ambient dust.

Reflecting Telescope – The Dobsonian Reflector: This type of reflecting telescope works on the same physical principles as most reflectors, but has a unique alt-azimuth mount. The optical tube assembly is usually made from a lightweight material, such as sono-tube cardboard or aluminum. Instead of an equatorial mount, the telescope body has two side bearings which fit into a cutout on a rocker box assembly allowing it to move freely up and down. The rocker box bases swivels 360 degrees, which provides lateral movement. When balanced correctly, the dobsonian reflecting telescope is very easy to use. By not having an expensive and heavy equatorial mount, larger aperture also becomes more cost efficient.

Reflecting Telescope – The Schmidt Cassegrain Reflector: This type of reflecting telescope is a hybrid of both lenses and mirrors. The primary light gathering source is parabolic primary mirror which redirects the light to a hyperbolic secondary mirror held in place by a lens arrangment which covers the end of the telescope tube. The light is then redirected back through a hole in the primary mirror to the eyepiece located at the back of the telescope. This reflecting telescope design "folds" the light path, allow for longer focal ratios and higher magnification. Astrographs, Ritchey-Chretien and Dall-Kirkham are also variations on the Schmidt-Cassegrain reflecting telescope design.

Reflecting Telescope – The Radio Telescope: Who said a reflecting telescope could only collect light waves? That's only part of the electromagnetic spectrum! The radio telescope is also a form of a reflecting telescope because it collects radio waves in a parabolic dish and refocuses them to a collection point.

Reflecting Telescope – Space Telescopes: The most famous of all reflecting telescopes is the Hubble Space Telescope. It uses its huge primary mirror to gather the electromagnetic spectrum far above Earth and our blocking atmosphere. Optically, the HST is a Cassegrain reflector of Ritchey-Chretien design and the information it processes is collected in a charge coupled device (CCD). Astronomical data taken with the CCDs are then calibrated for astronomical analysis.

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Have you ever wondered what it would be like to look through a telescope, but don't have one? Are you curious if there is such a thing as an online telescope? The answer is yes. If you have a computer, you can use it to virtually look through the eyepiece of a telescope… and even aim it at the objects of your choice!

One of the most exciting concepts to come about in a long time is the SLOOH Space Camera. Here's an opportunity to look through a variety of online telescopes located around the world and take a look at space from the comfort of your home. It's not difficult and you don't need complicated instructions to use it. SLOOH’s patented instant-imaging technology and user-friendly interface let's astronomers of all ages and skill levels remotely control a real telescope!All you need is a Mac or PC computer and Internet browser to explore the deepest reaches of space. To use the Slooh online telescope you must become a member of the Club, which includes mission cards, activity books, and online gift certificates. Once enrolled, you can articipate in group missions or control the online telescopes yourself. Says PC Magazine: "Would-be astronomers can gaze at live images of the night sky, but in the comfort of their homes. Kids – even big ones will marvel when they see the Andromeda Galaxy and other distant objects slowly materialize on their computer screens."

If you're a bit more advanced and would like to try your hand at astrophotograpy with an online telescope, then check out Global Rent-A-Scope. GRAS also has a variety of telescopes positioned in observatories around the world, and you can view live images as they are being created by remote astrophographers. Because taking images of the sky can involve very costly equipment and years of practice, how cool would it be just to tap into an on-line telescope and begin imaging? Now it's as easy as taking lessons and renting the equipment – and you don't even need clear skies or a special place to go. It's as close as your PC!

Another type of opportunity to enjoy an online telescope in a different format is the WorldWide Telescope. While this online telescope doesn't offer "live" views, the WorldWide Telescope (WWT) will allow your computer to act as a virtual telescope by displaying images from the foremost ground and space-based telescopes. You can even take a tour of all the most incredible places in space narrated by a real astronomer! This online telescope can provide views in multiple wavelength. Imagine seeing an x-ray view of a supernova and fading into visible light! Now you can take a look with H-alpha to view star-forming regions and examine high energy radiation coming from nearby stars in the Milky Way. Are you skies clouded out? No more. With the WorldWide Telescope you can view the Moon and planets anytime, from any location on Earth and any time in the past or future!

Would you like to use an online telescope to look at our nearest star? Then take a look at Eyes On The Skies. This simple and easy to use website offers "live" views of our Sun with an online telescope. This is the home of the internet-accessible robotic solar telescope, built by Tri-Valley Stargazers member Mike Rushford. Of course, you can only control the online solar telescope if the skies are sunny in Livermore California, USA!

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Have you ever wondered how to make telescope? You can make a telescope using ordinary household items and you can also make a telescope that competes with a manufactured model for only a few hundred dollars. To begin, all you need to do is understand the principles of what makes a telescope work. Let's start off simple…

How To Make A Telescope From Household Items: For this simple telescope, you will need some aluminum foil and one magifying lens. The lens doesn't need to be anything more complex than an ordinary toy magnifying glass. Instead of needing an optical tube assembly, your arms will become the telescope body and the magnifying glass will act as the telescope's objective lens. First we'll create an "eyepiece" by puncturing a hole in a tiny piece of foil. Begin by holding your pinhole eyepiece against your eye and look at a brightly lit scene. Now, put the magnifying lens against it and move slowly outward. You'll know when it's working! Try different distances and see where the image appears right side up – or upside down. Then try putting the pinhole eyepiece in front of the lens and you'll be surprised! The pin hole in the foil removes image blur. To make a more precise pinhole, layer the foil when puncturing and choose the best. Small holes seem to provide the best image, but experiment with them all. It's hard to believe you could make a telescope so simply, but it's true. The pinhole projector, minus the lens, has been in use for centuries and was the basis for one of the very first solar telescopes. However, remember your simple science principles and what happens when you focus the sun's rays through a magnifying glass. Your retina will burn far more quickly than any piece of paper! Never focus any kind of optical aid towards the Sun without a proper solar safety filter.

How To Make A Telescope – A Simple Refractor Telescope: Now let's add another toy magnifying glass lens (so we have one large and one small), a manila file folder and two cardboard tubes, with one that will fit inside the other. First let's determine the focal length of our lenses. You can do this easily by shining a flashlight into the lens and measure the distance inches from the lens to where it projects a small, bright point. Add the focal length of the two lenses together, divide by two and add one more inch. Cut both of your cardboard tubes to that length. Using the manila file folder, cut out two circles the same diameter as the cardboard tubes and cut a circle in the middle slightly smaller than the diameter of the two lenses. Run a bead of glue around the center hole and center your lens to be glued in place. When it is thoroughly dry, run a bead of glue around one end of both cardboard tubes and set your "lens cells" into place. When your glue as set, just slide the open end of the smaller tube into the open end of the larger tube and you have made your own simple refractor telescope! You can adjust the "focus" by the amount of slide.

How To Make A Telescope – The Telescope Kit: If you're interested in doing a classroom project there are many fine companies that offer inexpensive refractor telescope "kits". These kits can be as simple as the cardboard tube style which we have just explored, to elaborate models which replicate antique historical telescopes. A great project for your astronomy club or students is the Galileoscope, a replica of the "telescope that started it all".

How To Make A Telescope – The Dobsonian Reflector: If you find yourself fascinated with how to make a telescope and want to have a genuine astronomical instrument, you might be interested in getting some plans from the man himself – John Dobson. As the founder of the San Francisco Sidewalk Astronomers, John offers his Build Your Own Dobsonian Telescope Plans freely and all it takes is a little knowledge and the right parts. If you have a question about telescope making, or are looking for innovative design ideas, there are plenty of resources available such as the Amateur Telescope Maker webpages.

Have fun learning how to make a telescope!

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I've had a couple of readers write me, wondering what was going on with all the Celestron telescope reviews. Are we sponsored by Celestron, or something? Nope. Let me just make this clear. We don't get any money from any of the telescope manufacturers, or any kind of sponsorship at all. If and when we do, I'll let you know.

So far, Celestron, Vixen and Sky Watcher are the only telescope manufacturers willing to send out a telescope for us to review, and then willing to pay for the return shipping to take it back off our hands again. If I have to pay to receive a telescope, or ship it back, we can't afford to review it on Universe Today.

I know that really sets the bar pretty low. Universe Today received almost 2 million visitors last month, with 50,000 people subscribed to the RSS feed and daily email newsletter. Many of them are very interested in owning a telescope and would love to read about all the telescopes on the market. But I'm honestly exhausted trying to justify this to the manufacturers.

But so we're clear, we're not paid to give Celestron good reviews. If Tammy comes across as kind of enthusiastic in her reviews, well… that's Tammy; she's an enthusiastic force of nature. The manufacturers pay to ship the telescopes to and from our reviewers (well, Tammy), and then I pay Tammy for her reviews. If the telescope companies advertise on Universe Today, through Google, or through direct advertising, it doesn't influence what Tammy has to say about them.

And if you're a telescope manufacturer who wants to join this elite club of companies getting reviews on Universe Today, you just need to pay for the shipping. And if you want to advertise on Universe Today, just drop me an email.

P.S. I picked up a Celestron First Scope for the, uh, kids, and I really like it. Thanks to Tammy for the review, and thanks to the IYA for helping get it built.

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This artist's conception shows the newly discovered super-Earth GJ 1214b, which orbits a red dwarf star 40 light-years from our Earth. Credit: Credit: David A. Aguilar, CfA

More exoplanets this week! Today astronomers announced the discovery of so called super-Earth around a nearby, low-mass star, GJ1214. The newly discovered planet has a mass about six times that of Earth and 2.7 times its radius, falling in between the size of Earth and the ice giants of the Solar System, Uranus and Neptune. But this latest exoplanet, GJ1214b, has something else, too: an atmosphere about 200 km thick. "This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it," said David Charbonneau, lead author of a paper in Nature reporting the discovery, "but these conditions are still very interesting, as they could allow for some complex chemistry to take place."
Read more…

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Like many descriptors associated with telescopes, the term "dobsonian reflector" doesn't refer to the type of telescope – but rather the type of telescope mount. Often lovingly referred to as just "Dob", this simple alt-azimuth design cabinet mount was first conceived by amateur astronomer, John Dobson. His name is attached to the Dobsonian reflector telescope, a design for Newtonian reflectors based on low-cost materials.

The Dobsonian reflector is based on the idea that a telescope can be inexpensive and easy to use. It doesn't matter if it is made of cardboard, plywood, or even plastic pipe. The Dobsonian reflector is nothing more than a well-spaced set of mirrors in an optical tube assembly and mounted on a rocker box with side bearings – which in turn is set on a spinning base like a lazy susan. When the weight is balanced correctly on the side bearings, the dob telescope becomes incredibly easy to use with nothing more than up and down and side to side movements. Unlike the equatorial mount, there are no gears to strip and nothing complicated. While the design may seem at first to have some drawbacks, it didn't take long before talented amateur telescope makers were soon adding setting circles and encoders to the arrangements to allow for alternative aiming methods as well!

In the late 1980's the Dobsonian reflector design soon hit the telescope manufacturing business and became instantly popular. With less moving parts, the simple alt-az cabinet was very cost effective to manufacture and the major companies offered ever larger mirrors and prices backyard astronomers could afford. While even a refractor telescope can be mounted in a dobsonian cabinet, the Dobsonian reflector has endured because of affordable aperture. With time, the design even evolved to include truss-tubes and off-axis models.

Because of simple freedom of choice to use whatever materials are handy and affordable, the Dobsonian reflector "light bucket" is one of the most popular telescopes today!

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When it comes to Meade telescopes, it's important to understand that certain designations may not apply to the telescope type itself – but the mount type. This is the case with the Meade LXD75 series of telescopes. First let's take a look at what the Meade LXD75 is…

Meade LXD75 Mount – The Meade LXD75 is a German Equatorial Telescope Mount with an on-board weight capacity of up to 30 pounds. It is a shaft and bearing system which moves on four high-precision stainless steel ball bearings. Worm gears are located on both axes for smooth tracking and slewing – either via a remote system or physical slow motion controls. The Meade LXD75 mount utilizes an electronic High Precision Pointing 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 – also known as PEC – corrects periodic drive errors on the RA axis over the course of one or more training periods, thereby minimizing guiding corrections during long-exposure photography. The AutoStar hand control provides 9 different slew (movement) speeds, with a rapid slew rate of 4.5º/sec. to 1x sidereal. The AutoStar unit provided with the Meade LXD75 will help you quickly find and GoTo over 30,000 objects, such as planets, stars, galaxies, nebulae, and comets. The Meade LXD75 AutoStar is pre-programmed with several guided tours, including the popular Tonight's Best. Just Input date, time and location, then let AutoStar take you on a guided tour of the best objects in the sky for that particular night. The AutoStar controller provided with the LXD75 can be updated – simply log on to Meade.com to download software upgrades, guided tours, and timely objects like comets – all for free. Keep your Meade AutoStar up-to-date and your telescope will grow with you for years to come. Meade LXD75 also comes with a polar alignment scope and variable-height, heavy-duty field tripod with spreader bar brace provides the stability and vibration damping required for visual observation and astrophotography. It is powered by eight (8) D-size batteries, but can be adapted to other sources by optional car accessory plug or AC wall adapter.

Now let's take a very brief look at the various Meade LXD75 telescope models:

Meade LXD75 ACF-8AT Telescope – This is a less costly alternative to other Meade ACF telescopes. Meade Advanced Coma Free (ACF) optics are mounted in precision-machined aluminum cells and mounted in sturdy steel tubes which 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. The corrector lens fully corrects for spherical aberration and provides pinpoint star images. Water white glass is used in all corrector lenses to maximize light transmission. The use of water white glass results in an increase of light transmission in excess of 10%, as compared to competing telescopes using soda lime glass.

Meade LXD75 SC-8AT – This telescope offers Meade Schmidt-Cassegrain optics on the portable LXD75 mount. Focal length of 2000mm, focal ratio of f/10, with Ultra-High Transmission Coatings (UHTC) for maximum image brightness, sharpness, contrast, and coma-free flat fields. Schmidt-Cassegrain optics are mounted in precision-machined aluminum cells and mounted in sturdy steel tubes which 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. 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.

Meade LXD75 SN-6, SN-8 and SN-10 – 6", 8" and 10" Schmidt-Newtonian Telescope – The Schmidt-Newtonian is a unique design for both observing and astrophotography. Employing Meade corrector lens technology, Schmidt-Newtonians have just 1/2 the coma of standard Newtonians (coma is a fuzzy-star aberration that occurs in standard Newtonian and Dobsonian reflectors). These scopes are versatile, portable, and high-tech. Schmidt-Newtonians have extremely fast, well corrected f/Ratios for short photographic exposure times and wide fields-of-view. Available in 6", 8" and 10" aperture sizes with premium-grade Pyrex mirrors, well corrected f/Ratios, individually figured corrector plates and ultra-high transmission coatings all add up to a superior optical system.

Meade LXD75 AR-5 and AR-6, 5" and 6" Refractor Telescope – This classic achromatic refractor telescope design is also the most expensive per inch of aperture. However, refractor telescopes are known to provide incomparable resolution in high-contrast images of the Moon, planets, and deep space objects. Less expensive than an apochromat, the 2-element Meade LXD75 AR refractor is an excellent choice for any astronomer who’s looking for the crisp resolution of a refractor at a reasonably affordable price. Achromatic precision lens, well corrected f/Ratios and individually figured optics all add up to a superior optical system.

Meade LXD75 N6-AT Reflector Telescope – The 6" Newtonian Reflector is like a little brother to the Meade LightBridge Dobsonians. It shares many of the same practical benefits, such as an inexpensive Newtonian design. However, unlike a Dobsonian, the Meade LXD75 Newtonian has a Deluxe AutoStar controller and motorized drives that will automatically GoTo and track over 30,000 celestial objects. The scope has enough aperture to offer a serious step up from the average starter scope, remain lightweight, portable, and relatively inexpensive.

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The Meade ETX-125PE eliminates the beginning astronomer's two biggest challenges to enjoying the night sky – aligning their telescope and finding objects. According to Meade telescopes: "Just because a star may be millions of years old, doesn't mean it should take you that long to find it." Let's take a closer look at the Meade ETX-125PE telescope…

Meade ETX-125PE Premier Edition Telescope – The high-tech electronics that come with your Meade ETX-125PE Premier Edition Telescope automatically levels your telescope, points it North and sets the time. All you will need to do is just enter your location or zip code. After your Meade ETX 125PE completes its automatic alignment procedure it will head towards the first alignment star. Use the included wide-field SmartFinder to center the red dot over the alignment stars for accuracy. It's that easy. The ETX(R) (short for Everyone's Telescope) optics rival most expensive telescopes, and with computerized star-finding capabilities, and decent mount, the Meade ETX-125PE is a splendid entry-level telescope.

Meade ETX-125PE Premier Edition Telescope Maksutov-Cassegrain optical design out-performs many telescopes of larger apertures. Sky & Telescope said, "(ETX) stellar diffraction patterns were virtually textbook perfect." The compound optical design includes primary mirrors larger than the telescope's listed aperture to capture more light and a Flip-Mirror System that permits viewing either straight through or at a 90° position, and allows camera attachment with optional T-adapter. UHTC, Meade's exotic multi-layer optical coatings, optimize light transmission and image brightness is increased by 15% over standard coatings. Objects appear significantly brighter.

The Meade ETX-125PE is completely computerized and includes Deluxe AutoStar Controller with 30,000 object database. The precisely engineered high-torque motors included with the Meade ETX-125PE telescopes permit electronic operation in either altazimuth or equatorial mode. Control your Meade ETX with your choice of nine different speeds and included planetarium software can also control your Meade ETX from your PC (Windows(R) compatible). Adjustable, rigid tripod makes a great platform for any application – from daytime observing to beginning astrophotography. The Deluxe Field Tripod works in either altazimuth or equatorial mode and is fully adjustable adjustable to match any height adult or child. Additional items include Motorized Dual-Axis Drive System, Automatic Alignment and Smart Finder,Eyepiece, Planetarium Software, Training DVD, Tripod Carry Case and more.

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The word "refractor" means a telescope whose principal focusing element is a lens. A refractor telescope is a type of optical telescope which is also referred to as a refracting telescope. Its curved primary – or largest – lens gathers light, bends it, and sends it back to a focal point where it is further modified by the use of an another set of lenses called the eyepiece. The curvature and size of the primary lens dictates the amount of distance needed to achieve the focal point. The larger it becomes, the longer it must become… and early refractor telescopes were huge affairs! Let's take a look at the refractor's history…

Refractor History – The refracting design was first used in spyglasses, then later in astronomical telescopes and telephoto camera lenses. These first spyglasses were designed by two men – Hans Lippershey and Zacharias Janssen. Of course, this type of technology has great military implications and it wasn't long before several countries were putting their best opticians to work designing refractors for themselves. Thankfully Galileo Galilei heard about this new combination of lenses and what they could do – and independently designed his own refractor. While it only magnified the image about 30 times, rather than turn it towards incoming enemies, Galileo turned it towards the night sky and created the first astronomical telescope. By changing the convex, concave structure of the lens arrangements, other refractor telescopes were also developed, including the Keplerian telescope.

Refractor Design – While the refractor delivered incredibly sharp images, it wouldn't be long until problems developed. In all image respects, the more light gathered means better views – and larger optics were needed to gather that light. Beginning glass-making processes were primitive and large lenses meant the introduction of air bubbles and defects. What's worse, passing the electromagnetic spectrum through glass also meant the loss of some wavelengths and huge lenses bowed to the weight of gravity – further distorting the images. As time went on, astronomical refractor telescope designs changed as additives were combined with the lens elements to create ever better and more pure lenses. Opticians learned to combine lenses to reduce the focal length and compensate for optical errors. However, the refractor could never escape the weight of gravity! To this date, the largest achromatic refractor ever put into astronomical use is the 40-inch (1.02 m) Refractor, at Yerkes Observatory.

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Are you ready to learn more about the reflecting telescope? Then let's start by taking a look at what each word means. To "reflect" is to to cast back (light, heat, sound, etc.) from a surface. It also means to give back or show an image. The word "telescope" refers to an instrument designed for the observation of remote objects by the collection of electromagnetic radiation – radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Therefore, taken in a literal sense, a reflecting telescope is a tool which returns information and images across a full spectrum. It consists of one or more curved mirrors which gather and refocus the spectrum to a single point for study.

Reflecting Telescope History – The first reflecting telescopes appeared sometime during the 17th century. Although the principle behind using a curved mirror as a lens was known some 600 years earlier, it was difficult to produce parabolic mirrors that returned a satisfactory image. In the mid-1600s, James Gregory published his ideas for a reflecting telescope, but it would be a decade later before Robert Hooke would construct the first working model of the Gregorian reflector. During this time, Sir Isaac Newton also built his first speculum mirror reflecting telescope and his optical design has endured the test of time.

Reflecting Telescope Types – Through our history, we have learned of two reflecting telescope types – the Gregorian and Newtonian reflectors. As time passed, optical perfection increased and designs expanded to perfect the returned image as well. These "newer model" reflecting telescopes include the Cassegrain telescope, the Ritchey-Chretien telescope, the Dall-Kirkham Cassegrain telescope, the Herschelian telescope, the Schiefspiegler telescope, Nasmyth telescope and the Yolo-style reflector. There are even reflecting telescopes that have a liquid primary light gathering source!

Reflecting Telescope Uses – While the original intent of the reflecting telescope was to gather, focus and magnify visible light for study, the beauty behind the design is that it is able to gather the virtual electromagnetic spectrum. Almost all of the major telescopes used in astronomy research are reflectors – even the Hubble Space Telescope! Why a reflecting telescope instead of a glass element refractor? Because certain wavelengths are absorbed when passing through glass elements and astronomers want to study all the wavelengths to get the most and best possible information. Even a radio telescope is a type of reflecting telescope!

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The Meade LX90 is one of Meade Telescope's most popular designs. With its great combination of highly usable electronic features, solid and relatively light weight mount, and very reasonable cost, goes to the next level with larger optical systems. However, did you know the Meade LX90 comes in two very different designs? Then let's take a look…

Meade LX90 ACF (Advanced Coma-Free) Telescope – The Meade LX-90 ACF series has a flat, coma-free field similar to that of designs used in most professional observatory telescopes and the Hubble Space Telescope, but at a down-to-Earth price. Its coma-free field is well suited for astrophotography and the large aperture size gathers enough light to keep visual observers happy for a life-time. Standard equipment includes a GPS (Global Positioning Satellite) receiver, proprietary LNT (Level North Technology), and AutoAlign software embedded in the AutoStar computer. This makes for a telescope that's incredibly simple to set up and to use. The Meade LX90-ACF Advanced Coma-Free Telescope new optical design reduces the astigmatism and eliminates diffraction spikes that delivers coma-free pinpoint star images and flatter field that discerning astrophotographers and most professional observatories expect. The Meade LX90 ACF is the perfect platform for the demanding visual observer and imaging enthusiast with telescopes available in apertures of 8 inches, 10 inches, and 12 inches.

Meade LX90 SC (Schmidt-Cassegrain) Telescope – The Meade LX90-SC Telescope comes with classic Schmidt-Cassegrain optics resulting in a high quality, yet more economical, telescope package. The addition of UHTC (Ultra-High Transmission) coatings provide outstanding visual performance and clear, bright images from an over-sized primary mirror with diffraction limited optics. This additional 1/4" yields a wider, fully illuminated field-of-view, and allows you to see the light other telescopes leave behind. All Meade LX90 models feature the solid and stable LX90 aluminum double fork mount, advanced Meade 497 AutoStar computer system with over 30,000 object library, multiple guided tours, High Precision Pointing capability, heavy duty tripod and Meade SmartDrive with Permanent Periodic Error Correction. What's more, you get a 1.25" diagonal prism, Series 4000 26mm 5-Element Plossl eyepiece, and Meade AutoStar® Suite Astronomer Edition Software for PC. The telescope also includes two separate viewfinders: an easy to use zero magnification red dot viewfinder controlled via the keypad with adjustable brightness and blink functions, and additionally a conventional 8×50 optical viewfinder with quick release bracket. The Meade LX90 is the perfect platform for the demanding visual observer and imaging enthusiast!

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