Celestron OMNI XLT 102 manual Aligning the Finderscope, Calculating Magnification

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Aligning the Finderscope

Accurate alignment of the finder makes it easy to find objects with the telescope, especially celestial objects. To make aligning the finder as easy as possible, this procedure should be done in the daytime when it is easy to find and identify objects. The finderscope has a spring-loaded adjustment screw that puts pressure on the finderscope while the remaining screws are used to adjust the finder horizontally and vertically. To align the finder:

1Choose a target that is in excess of one mile away. This eliminates any possible parallax effect between the telescope and finder.

2Release the R.A. and DEC clamps and point the telescope at your target.

3Center your target in the main optics of the telescope. You may have to move the telescope slightly to center it.

4Adjust the screw on the finder bracket that is on the right (when looking through the finder) until the cross hairs are centered horizontally on the target seen through the telescope.

5Adjust the screw on the top of the finder bracket until the cross hairs are centered vertically on the target seen through the telescope.

Image orientation through the finder is inverted (i.e., upside down and backwards left-to-right). This is normal for most astronomical finderscopes. Because of this, it may take a few minutes to familiarize yourself with the directional change each screw makes on the finder.

Calculating Magnification

You can change the power of your telescope just by changing the eyepiece (ocular). To determine the magnification of your telescope, simply divide the focal length of the telescope by the focal length of the eyepiece used. In equation format, the formula looks like this:

Focal Length of Telescope (mm)

Magnification = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

Focal Length of Eyepiece (mm)

Let’s say, for example, you are using the 25mm eyepiece that came with your telescope. To determine the magnification you simply divide the focal length of your telescope (the Omni XLT 102 for this example has a focal length of 1000mm) by the focal length of the eyepiece, 25mm. Dividing 1000 by 25 yields a magnification of 40 power.

Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The general rule is that 60 power can be used for every inch of aperture. For example, the Omni XLT 102 is 4 inches in diameter. Multiplying 4 by 60 gives a maximum useful magnification of 240 power. Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 80 to 140 times for the Omni XLT 102 telescope. You can determine the magnification for your telescope the same way.

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Contents Omni XLT Series Telescopes Table of Contents Astrophotography Page Omni XLT 102 Refractor Omni XLT 150 Newtonian Omni XLT 127 Schmidt-Cassegrain Setting up the Tripod Attaching the Equatorial Mount Attaching the Center Leg Brace Installing the Counterweight BarAttaching the Slow Motion Control Knobs Cables Installing the CounterweightsAttaching the Telescope Tube to the Mount Installing the Visual Back Installing the FinderscopeInstalling the Eyepieces Installing the Star DiagonalBalancing the Mount in R.A Moving the Telescope ManuallyBalancing the Mount in DEC Adjusting the MountAdjusting the Mount in Azimuth Adjusting the Mount in AltitudePage Page Image Orientation FocusingCalculating Magnification Aligning the FinderscopeGeneral Observing Hints Determining Field of ViewCelestial Coordinate System Motion of the Stars Pointing at Polaris Latitude ScaleFinding the North Celestial Pole Polar Alignment with the Latitude Scale Polar Alignment in the Southern HemisphereFinding the South Celestial Pole SCP Pointing at Sigma OctantisDeclination Drift Method of Polar Alignment Aligning the R.A. Setting Circle 11 Vernier Scale Using the R.A. Vernier ScaleLunar Observing Hints Observing the MoonObserving the Planets Planetary Observing HintsSolar Observing Hints Observing the SunObserving Deep Sky Objects Seeing ConditionsSeeing Using the Lens Cap Aperture Stop with Refractor TelescopesPiggyback Photography Using Digital Cameras Full Eyepiece Projection for a Schmidt-CassegrainLong Exposure Prime Focus Photography Planetary and Lunar Photography with Special Imagers Terrestrial Photography CCD Imaging for Deep Sky ObjectsMetering Reducing VibrationCollimation of Refractors Care and Cleaning of the OpticsTwo 2 turns Collimation of a Schmidt-CassegrainCollimated telescope Should appear Symmetrical with Aligning the Secondary Mirror Collimation of a NewtonianBoth mirrors aligned with your eye looking into the focuser Night Time Star Collimating As a Series 1 # Page Page Appendix a Technical Specifications Appendix B Glossary of Terms Page Page Page Page Page Page Page Page Celestron Two Year Warranty
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