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Celestron Omni XLT 127 Telescope


The Celestron Omni XLT 127 represents an entry level 5-inch Schmidt-Cassegrain telescope on a sturdy German equatorial mount. Schmidt-Cassegrains pack a large aperture into a smaller and lighter package. This is a fine 5-inch telescope for anyone facing size and weight restrictions.


Item #ProductStock StatusPriceShipping
11084Celestron Omni XLT 127
Normally Ships in 7-10 Days
$689.00
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Optical Specifications: Celestron Omni XLT 127
Type Schmidt-Cassegrain
Aperture (mm) 127 mm
Aperture (in.) 5 inches
Focal Length 1250 mm
Focal Ratio f/10
Accessories and Features
Included Eyepiece(s) 25mm Plossl
Finder 6 x 30 Optical
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> Not Recommended
Physical Parameters
Weight, Optical Tube 6.5 Pounds
Weight, Mount 33.5 Pounds
Weight, Fully Assembled 40 Pounds
Optical Tube Length 11 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>