Celestron 4" Omni XLT 102 Equatorial Refractor with Starbright XLT Optical Mount

This Celestron Omni XLT 102 refractor puts good fully Starbright XLT multicoated achromatic optics on a solid German equatorial mount to provide an excellent mix of performance, portability, and features at a price that's surprisingly low.

The Celestron Omni XLT 102 refractor combines quality optics with a solid German equatorial mount - at a remarkably sensible price for a scope of its quality. It provides an excellent mix of performance, portability, stability, and features that any serious backyard astronomer can appreciate.

For the observer whose interests are the brighter solar system and deep space objects, the Omni XLT 102 has a lot to offer. It is exceptional for observing within the solar system. Its views of subtle lunar and planetary details are sharp and contrasty, bringing the planets to vivid life in the eyepiece.

It has a sensibly large aperture and diffraction-free images that make it surprisingly good for much deep space observing, as well. Binary stars and globular star clusters are particularly well-resolved and vivid, with the contrasting colors of many binary systems showing nicely. The brighter nebulas and galaxies stand out against a darker sky background than is possible in a comparably-priced reflector with its light-scattering diagonal mirror.

This Telescope's Optical System . . .

Refractor optics: 4" (102mm) aperture, 1000mm focal length, f/9.8 achromatic doublet lens using aspheric shaping technology for images that have virtually no spherical aberration. The lens cell is fully collimatable for optimum sharpness. The optical tube length is a very manageable 39.5".

Starbright XLT multicoated optics: Fully coated on all air-to-glass surfaces with multiple layers of magnesium fluoride and hafnium dioxide antireflection coatings for the highest possible light transmission and contrast. They are the same coatings used on Celestron's largest most expensive optical systems.

Lens cap/aperture stop: A protective lens cap is provided to cover the objective lens of the telescope and keep it dust-free when the scope is not in use. This lens cap has a built-in aperture stop in the center. When observing the Moon and planets, leaving the lens cap on the telescope with the aperture stop removed will reduce the scope's chromatic aberration (the faint halo of violet light or "spurious color" visible around very bright objects in all achromatic refractor telescopes). The scope's resolution will be slightly reduced, but eliminating the spurious color provides a generally more pleasing image for most observers. The lens cap should always be completely removed when observing faint deep sky objects such as nebulas and galaxies, where aperture (light-gathering) is essential and chromatic aberration is not an issue.

Dew shield: Slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. Also improves visual and photographic contrast by shielding the lens from off-axis ambient light (the neighbor's yard light, moonlight, etc.)

Rack and pinion focuser: 2" focuser, with 1.25" eyepiece adapter. Dual focusing knobs with rubber gripping surfaces for precise image control with either hand. The large focus knobs are easy to operate, even while wearing gloves or mittens in cold weather. The eyepiece holder has built-in T-threads for attaching an optional T-ring and camera for prime focus photography.

Star diagonal: 90° viewing angle prism-type 1.25" star diagonal.

Eyepiece: Fully multicoated low power 1.25" 25mm (40x) eyepiece with a 1.25° field of view (two and a half times the diameter of the full Moon).

Finderscope: 6 x 30mm straight-through achromatic design, with a wide 7° field of view. Focuses by loosening the trim ring behind the objective lens cell, screwing the lens cell in or out to focus, and tightening the trim ring to lock in the correct focus.

This Telescope's Mount . . .

CG-4 German equatorial mount: The mount has setting circles in both right ascension and declination, worm gear drives and manual slow motion controls in both axes, a latitude scale and fine adjustment controls in both altitude and azimuth, two counterweights totaling 11 pounds so you can easily balance virtually any accessory load, and more. An optional dual axis DC drive/drive corrector is available for no-hands tracking of celestial objects and photography. It is not possible to upgrade to a computerized go-to drive system. For more details, click on the link in the support tab above.

Adjustable height tripod: The tripod has 1.75" diameter steel legs with a center leg brace for rigidity. It adjusts over a height range from 33" to 47". Vibration damping characteristics are excellent. The center leg brace is drilled to form a convenient accessory tray that holds 1.25" and 2" eyepiece to keep them up out of the dew-soaked grass.

Dovetail tube mount: The scope's optical tube rings are connected to a mounting plate that slips into a dovetail groove on the mount's equatorial head. Setup and takedown times are exceptionally fast, as a single large hand-tighten knob holds the optical tube in place. A second lock knob prevents the tube from sliding off the mount should the hand-tighten knob accidentally loosen while observing.

Two-year warranty: All Celestron telescopes have a two-year warranty.

With a relatively short 1000mm focal length and a light grasp 212 times that of the sharpest dark-adapted eye, the scope is capable of producing surprisingly bright wide-field images of the faint fuzzies outside the solar system - nebulas, galaxies, open star clusters, and more.

But those objects requiring high power and high contrast - globular clusters, close binary star pairs, lunar and planetary images, etc. - are where this achromatic scope shines. Using optional eyepieces and/or a Barlow to boost the magnification, you can see subtle solar system details that are virtually invisible in smaller aperture scopes. You can study lunar craters, rilles, mountain ranges, and low contrast lunar ray detail. With reasonable seeing conditions, detail in Jupiter's cloud belts and the Great Red Spot (actually closer in color to the Faint Pink Spot at this point in time) are visible, as are dusky markings on the face of Saturn and Cassini's division in Saturn's brilliant rings. Chromatic aberration is present in the scope when viewing very bright objects, as it is in all achromatic refractor telescopes, but using the lens cap/aperture stop mentioned above will reduce its visibility.

Optically and mechanically refined, and very reasonable in cost for a 4" refractor, this Celestron Omni XLT 102 has enough optical performance to keep you busy for the rest of your life.