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Celestron Omni XLT 102


The Celestron Omni XLT 102 sits at the border between large and small refractors. While any good small refractor can deliver exquisite views of the moon and planets, a four-inch refractor has the potential to show a myriad of deep space objects.


Item #ProductStock StatusPriceShipping
21088Celestron Omni XLT 102
In Stock - Ships Same Day (business days) This is "live" inventory data. If it says in stock, you can believe it.
$419.00
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Celestron Omni XLT 102 Telescope

The Omni XLT 102 is a good choice for those primarily interested in observing the moon, planets, and some of the brighter deep space objects. As with any telescope, the potential is subject to your local skies. A four-inch refractor reveals the veil nebula under magnitude 5.5 skies, as well as the spiral arms of the Whirlpool Galaxy under magnitude 6.5 skies. Neither of these sights are practical using even an eight-inch telescope under light polluted urban skies with a limiting magnitude of less than four. The f/9.8 optics of this telescope allow it to reach higher magnifications than fast focal ratio refractors of similar aperture. This telescope should easily handle 180-200X magnification, which many of us find to be a sweet spot for serious planetary observation.

The Omni XLT 102 is supplied with Celestron's CG-4 mount. This medium duty German equatorial mount is more than adequate to the task of handling this telescope. When properly polar aligned it will track your target by simply turning the slow motion control on the right-ascension axis.

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Optical Specifications: Celestron Omni XLT 102
Type Achromatic Refractor
Lens Cell Type Air Spaced Doublet
Aperture (mm) 102 mm
Aperture (in.) 4 inches
Focal Length 1000 mm
Focal Ratio f/10
Magnification (w/supplied eyepiece) 40X
Limiting Visual Stellar Magnitude <p><b>Limiting Stellar Magnitude</b><br /> This is a measure of the faintest star that can be seen with a telescope under ideal conditions. We include this figure for the purpose of comparing two telescopes of different apertures using a consistent scale. Many manufactures publish this specification. Unfortunately manufactures use different methods to calculate this figure, rendering the numbers useless for direct head to head comparison of different brands of telescopes. </p> <p>Limiting stellar magnitude is the sum of the naked eye limiting magnitude and the telescopic gain. The naked eye limiting magnitude varies by location due to local light pollution; therefore, it is an assumption. This figure could be 6.5 or higher at some of the darkest locations, but less than 2 in the middle of a large city. Our calculations assume a figure of 5, which one might typically find 30-40 miles from a major urban area. </p> <p>Telescopic gain is a direct function of aperture. No attempt has been made to compensate for the affects of central obstructions or different types of optical coatings.</p> 12.7 Magnitude
Accessories and Features
Included Eyepiece(s) 25mm Plossl
Finder 6x30 Optical
Focuser Two-inch Rack and pinion
Star Diagonal 1.25-inch prism type
Accepts 2" Eyepieces <p><b>Telescope Eyepiece Formats</b><br /> Virtually all telescope eyepieces available today conform to one of two barrel diameter standards: 1.25 or 2 inches. Most amateur astronomers will be perfectly content with 1.25" eyepieces. Two-inch eyepieces have only one inherent advantage. That advantage is a potentially larger field of view, but not every telescope can take advantage of that potential. </p> <p>A Telescope and eyepiece work together to collect parallel light rays over a large area, compress those light rays down into a smaller area, and the re-orient them so that they are nearly parallel once again. Essentially light arriving at a telescope with any given aperture is compressed into a smaller aperture or exit pupil. The ratio of the telescope aperture to eyepiece exit pupil determines the magnification.</p> <p>There are cases at very low magnifications where the eyepiece barrel diameter becomes the constraint on maximum field of view. The eyepiece barrel itself actually blocks some of the available light that the telescope is collecting, thus limiting the field of view. Two-inch eyepieces overcome this constrain by allowing a larger light cone to enter the eyepiece. We must conclude this discussion by restating that 2" eyepieces have no inherent advantage over 1.25" eyepieces other than the potential for a larger field of view when used with a telescope capable of benefiting from that advantage. </p> No
Adaptable for 2" Eyepieces <p><b>Two-inch Eyepiece Upgrade</b><br /> Some telescopes that are factory configured for 1.25" eyepieces can be upgraded to accommodate 2" eyepieces. Other telescopes are designed to handle only 1.25" eyepieces and cannot be upgraded due to their focuser size or other constraints. </p> <p>Sometimes this upgrade is possible but not recommended. This could be due to clearance issues caused by the addition of a larger 2" star diagonal,which in some cases will bottom out on the base of a fork mounted go-to telescope. This is potentially damaging the drive mechanism. In other cases the light cone exiting the telescope may not be large enough to derive any benefit from a 2" eyepiece.</p> Yes
Physical Parameters
Weight, Optical Tube 9.5 Pounds
Mount Weight (including tripod and counterweight) 33.5 Pounds
Weight, Fully Assembled 43 Pounds
Optical Tube Length 39.5 Inches
Eyepiece Calculator
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Exit Pupil: <p>Exit pupil represents the diameter of the column of light exiting the eyepiece. Magnification is simply the ratio of telescope aperture to exit pupil. Fox example, using a telescope with 100mm aperture and an exit pupil of 2mm yields a magnification of 50X.</p> <p>There are both upper and lower limits to the useful range of exit pupils. The typical human eye pupil dilates to a maximum of 7mm when fully dark adapted. This figure decreases with age. Using an exit pupil that is larger than this upper limit simply spills the light onto an area of the eye not capable of receiving data. At the opposite end of the range, a smaller exit pupil means less area on the eye is collecting data. Images brightness decreases with decreasing exit pupil. Deep space objects grow dimmer rapidly as the exit pupil falls below 1 mm. The planets also start to become noticeably dimmer when the exit pupil falls much below 0.5 mm.</p> <p>Our eyepiece calculator provides warnings and error messages based upon the value of the exit pupil. These are intended to be guidelines as opposed to hard rules. There is no harm in violating these gidelines, but your enjoyment of the telescope may be diminished if you do. </p>