Celestron C4-R 102mm Refractor Telescope

!9# Celestron C4-R 102mm Refractor Telescope

Brand : Celestron | Rate : | Price :
Post Date : Oct 28, 2011 07:40:07 | N/A

Celestron C4-R 102mm Refractor Telescope

The Celestron C102HD telescope is regarded as a major bargain for good reason. Instead of computerized bells and whistles, you get the solid optical performance of a full sized four-inch achromatic refractor combined with a serviceable German Equatorial mount. Experienced observers frequently recommend the C102HD to beginning astronomers for one simple reason: it delivers great views of the planets.

How great are the views? In side by side tests, the C102HD consistently showed better contrast and more detail on Jupiter and Saturn than my five inch Schmidt-Cassegrain. On a night when my C5 showed five or six cloud belts across the face of Jupiter, the C102HD showed seven. On Saturn, when I push the magnification to 200X, the Cassini division is crisp, I see cloud belts on the planet; I see shading in the A and B rings, and even glimpse the Crepe ring. When looking at the star Epsilon Lyrae, the famous double-double, the C102HD showed me four crisp bright beads of light, without the bright diffraction rings and scattered light that I see in my C5.

One drawback: the CG-4 equatorial mount included with the C102HD is only barely adequate to support a forty-inch plus telescope. I found that it was better to set up on grass or gravel and leave the tripod about a foot short of full extension--this significantly reduces the vibration problems that otherwise trouble this mount.

What accessories would I recommend? Adding a CG4 motor drive significantly increased my viewing pleasure by allowing the telescope to track for long periods without my touching the controls. As with any equatorial mount, you need to point the Polar axis at the North Star, Polaris, for the tracking to work properly (don't worry, this is all explained in the manual). As for eyepieces, the included 20mm plossl eyepiece gives a magnification of 50X and a one degree true field of view. You'll want a 32mm eyepiece to take in the full view of star clusters like the Pleiades and the Double Cluster in Perseus. The Ultima 7.5mm is ideal for high power views of Jupiter and Saturn. I usually suggest a good star chart with any telescope, but for viewing the planets, a subscription to Sky and Telescope magazine might be even more useful; the planets, after all, move from one month to the next! --Jeff Phillips

Pros:

• Solid optical performer
• Great views of the planets

Con:

• Barely adequate mount

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Celestron 31057 Omni XLT ? 150

!9# Celestron 31057 Omni XLT ? 150

Brand : Celestron | Rate : | Price : $429.00
Post Date : Oct 19, 2011 16:16:39 | Usually ships in 1-2 business days

A premium optical system to explore the universe... The Omni XLT family of telescopes was designed to offer a selection of models with the quality optics and stable platform that serious amateurs can appreciate. The new Omni XLT Series features refractor, reflector and Schmidt-Cassegrain optical designs coupled with the new Omni CG-4 heavy-duty German Equatorial mount and sturdy tripod featuring 1.75" stainless steel legs and center tray for superior rigidity and vibration dampening. Along with the stable platform of the CG-4 mount the Omni XLT series features high quality optics. Using aspheric shaping technology in conjunction with hand-figuring the optics the Omni XLT presents an image with virtually no spherical abberation. Celestron also added the famous StarBright XLT coating system to further enhance light transmission. With superior optics and a stable platform the Omni XLT series is a great choice for astrophotography. Use the optional dual-axis motor drive (#93522) and polar axis finder (#94221) to track objects for long exposure photography. Four aperatures are available in the Omni XLT series, 102mm 120mm 127mm and 150mm, all with Starbright XLT Coatings. Locate and identify thousands of celestial objects on your laptop or PC with "The Sky" Level 1 software included FREE with every Omni XLT model. The series features a Tall finderscope mount for easier viewing through finderscope. Machined focus knobs for fine tuning fo

• High quality optics start with each lens and/or mirror being hand selected so only the finest grade of optical glass is used
• StarBright XLT coatings provide maximized light transmission
• 25mm multi-coated eyepiece, 20mm eye relief, 50 deg FOV
• CG-4 German Equatorial Mount with setting circles and slow motion controls to accurately locate and track sky objects
• Ball bearings in both axis of the mount for smooth performance

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How Newton's Telescope Changed the World

!9# How Newton's Telescope Changed the World

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Sir Isaac Newton is often considered the greatest astronomer and mathematician, in order to live forever. There are a lot of validity of this statement. This article looks at his famous reflector telescope and describes some of his discoveries.

A reflector telescope is one that uses a mirror rather than lenses to bend light and magnify images. Reflector telescopes, because they are easier and can be made much larger in size refractors, are an invention that changed astronomy andour understanding of the universe. The largest refracting telescope in the world is forty inches in diameter and reflector telescopes dwarf this comparison. There are currently several reflector type regions are over 400 cm in diameter.

Why a reflector is better than a refractor

If you are using a prism or a rainbow, you can understand why reflectors are superior to refractors. When light passes through glass the different bands (orColor) on the past at various angles and this causes aberrations or problems in the images. This is called chromatic aberration and gives us a distorted view of what we see through a lens. Make time to do Newton glass lens was very primitive, and the problems of chromatic aberration have not been exceeded. Today we can lentils, which have almost no chromatic aberration, but we can not be very large. If a lens to be really big, it will be very difficult and hisown weight will distort the lens and ruin the image.
 
Newton's telescope solved these problems. A mirror doesn't pass light through it. It simply bounces all the light off the surface. There is no chromatic aberration at all. And because you only need to bounce light off the surface you can place the whole mirror on a supporting structure or base which takes a lot of the weight off the mirror. This way you can build much larger mirrors without any distortion.
 
It is commonly thought that Newton invented the first reflector telescope but it isn't true. Credit for making the first reflector goes to and Italian Monk, Physicist, and Astronomer named Niccolo Zucchi. He published a book on Optics in the 1650's and it is this book that inspired Sir Isaac Newton to build his own telescope. Zucchi created his first reflector around 1616 while Newton completed his first (and famous) telescope in 1670. But while Zucchi did make some new discoveries with his telescope it didn't work well and was difficult to make and to use. It was Newton's telescope that worked really well and that brought the art and science of reflectors into the world of science.
 
The real Genius of Newton's Telescope
 
All of that stuff is remarkable but there is something much more important in Newton's Astronomy and in his telescope. He didn't after all, discover moons around Jupiter like Galileo did, or plot the return of a comet like Halley did. But what he did do was tie in Mathematics, Astronomy, and our understanding of the universe using his telescope and his theory of universal gravitation.  He proved mathematically that gravitation was a two way operation and that while the earth pulled on a falling apple so the apple too pulled on the earth. This was clearly seen, calculated, and confirmed in the motions of heavenly bodies which was refined and made possible by the new science of reflector telescopes which we can credit to Newton. 
 
Sir Isaac and his telescope carried on with the work of Copernicus and Galileo by furthering our understanding of the universe we live in and helping us to realize there are laws that govern the whole of the universe.  And this rule holds true for falling apples and for planets revolving around stars.
 
The actual telescope that Newton built still survives today and is in the care of the Royal Society of London. They keep it on display in London and sometimes it travels the world as part of an exhibit.

How Newton's Telescope Changed the World

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