Celestron XLT series Instruction Manual
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Celestron XLT series Instruction Manual

Omni xlt series telescopes
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Summary of Contents for Celestron XLT series

  • Page 1 ● ● ● ● ● ● ● ●...

  • Page 2: Table Of Contents

    Attaching the Center Leg Brace ... 10 Installing the Counterweight Bar... 10 Installing the Counterweights... 11 Attaching the Slow Motion Knobs ... 11 Attaching the Telescope Tube to the Mount... 12 Installing the Finderscope... 13 Installing the Visual Back... 13 Installing the Star Diagonal ... 14 Installing the Eyepieces ...
  • Page 3 Collimation of Refractors ... 39 Collimation of a Schmidt-Cassegrain... 40 Collimation of a Newtonian ... 42 OPTIONAL ACCESSORIES... 46 APPENDIX A TECHNICAL SPECIFICATIONS ... 49 APPENDIX B - GLOSSARY OF TERMS... 50 SKY MAPS... 53 CELESTRON TWO YEAR WARRANTY ... 59...

  • Page 4: Introduction

    This instruction manual covers all the different models of the Omni XLT telescopes. No matter at what level you are starting out, the Omni XLT Series telescopes will unfold for you and your friends all the wonders of the Universe.
  • Page 5 Figure 1-1 Omni XLT 102 Refractor Optical Tube Tube Rings Finderscope Eyepiece Equatorial Mount Latitude Adjustment Screw (Omni XLT 120 Refractor similar) 1.75" Steel Tripod Accessory Tray/ Leg Brace Counterweights Counterweight Bar Dovetail Slide Bar Objective Lens Shade...
  • Page 6 Figure 1-2 Omni XLT 150 Newtonian Finderscope Finderscope Bracket Focuser Eyepiece Tube Rings Equatorial Mount 1.75" Steel Tripod Accessory Tray/ Leg Brace Counterweights Counterweight Bar Dovetail Slide Bar Optical Tube...
  • Page 7 Figure 1-3 Omni XLT 127 Schmidt-Cassegrain Optical Tube Finderscope Finderscope Bracket Equatorial Mount Latitude Scale Accessory Tray/ Leg Brace 1.75" Steel Tripod Counterweights Counterweight Bar Declination Setting Circle Dovetail Slide Bar Schmidt Corrector Lens...

  • Page 8: Assembly

    Omni telescope models and the optical tubes have some differences which will be noted. Your Omni telescope should be set up indoor the first time so that it is easy to identify the various parts and familiarize yourself with the correct assembly procedure before attempting it outdoor.

  • Page 9: Attaching The Equatorial Mount

    The equatorial mount allows you to tilt the telescope’s axis of rotation so that you can track the stars as they move across the sky. The Omni mount is a German equatorial mount that attaches to the tripod head. On one side of the tripod head there is a metal alignment peg for aligning the mount.

  • Page 10: Attaching The Center Leg Brace

    Thread the accessory tray knob onto the central rod and tighten. o properly balance the telescope, the mount comes with a counterweight bar and two counterweights. To install e counterweight bar: . Remove the counterweight safety screw from the counterweight bar (at the opposite end of the threaded end).

  • Page 11: Installing The Counterweights

    Since the fully assembled telescope can be quite heavy, position the wards north before the tube assembly and counterweights are attached. This will make the polar lignment procedure much easier. Each Omni mount comes with two counterweights (One weights lbs. and the other weights 4 lbs.) To install the ounterweight(s): rient the mount so that the counterweight bar points toward the ground.

  • Page 12: Attaching The Telescope Tube To The Mount

    . Put the polar axis cap over the polar axis. It is held into place by a tension fit. he telescope optical tube attaches to the mount via a dovetail slide bar mounting bracket. For the refractors and the Newtonian, the mounting bracket is the long bracket...

  • Page 13: Installing The Finderscope

    Toward the rear of the t nt of the telescope tube (Newtonian), there is a small bracket with a set screw in it. This is where the finderscope bracket will be mounted. To install the find...

  • Page 14: Installing The Star Diagonal

    Refractors – To use the star diagonal on refractor telescopes, it is inserted into the 1 ¼” eyepiece adapter. The eyep iece, or ocular as it is also called, is an optical element that magnifies the image focused by the telescope. Without the eyepiece it would be impossible to use the telescope visually.

  • Page 15: Moving The Telescope Manually

    — GRADUALLY — to see which way the telescope “rolls.” 3. Loosen the counterweight locking screw on the counterweight. Move the counterweights to a point where they balance the telescope (i.e., it remains stationary when the R.A. clamp is released).

  • Page 16: Balancing The Mount In Dec

    In order for a motor drive to track accurately, the telescope’s axis of rotation must be parallel to the Earth’s axis o rotation, a process known as polar alignment. Polar alignment is achie...

  • Page 17: Adjusting The Mount In Altitude

    Screw imuth Adjustment For rough adjustments in azimuth, simply pick up the telescope and tripod and move it. For fine adjustments in azimuth: 1. Turn the azimuth adjustment knobs located on either side of the azimuth housing (see Fig 2-14). While standing behind the telescope, the knobs are on the front of the mount.

  • Page 18: Telescope Basics

    A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused. ome tele opes, known as re fractors, use lenses. Other chmidt- ssegrai elescop e uses both mirrors and len...
  • Page 19 The Schmidt-Cassegrain optical system (or Schmidt-Cass for short) uses a combination of mirrors and lenses and s referred as a compound or catadioptric telescope. This unique design offers large-diameter optics while maintaining very short lengths, making them extremely portable. The Schmidt-Cassegrain system consists of a zero power corrector plate, a spherica primary mirror, and a secondary mirror.

  • Page 20: Image Orientation

    When using the star diagonal with fractors and Schmidt-Cassegrains, the image is right-side-up, but reversed from left-to-right (i.e., mirror image). If inserting e eyepiece directly into the focuser of a refractor or the visual back of the Schmidt-Cassegrain (i.e., without the star diagonal), e image is upside-down and reversed from left-to-right (i.e., inverted).

  • Page 21: Aligning The Finderscope

    DEC clamps and point the telescope at your target. Center your target in the main optics of the telescope. You may have to move the telescope slightly to center it. Adjust 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.

  • Page 22: Determining Field Of View

    , multiply the angular field of 1.25 with our example of one thousand yards. The apparent field of each eyepiece that Celestron manufactures is found in the Celestron Accessory Catalog (# 93685). When working with any optical instrument, there •...

  • Page 23: Astronomy Basics

    Up to this point, this manual covered the assembly and basic operation of your telescope. However, to understand your telescope more thoroughl y, you need to know a little abou astronomy in general and includes information on the nigh To help find objects in the sky, astronomers use a celestial coordinate system that is similar to our geographical coordinate system here on Earth.

  • Page 24: Motion Of The Stars

    The d aily motion of the Sun across the sky is familiar to even the m st casual observer. This daily trek is not the Sun oving as early astronomers thought, but the result of the Earth's rotation. The Earth's rotation also causes the stars to o the same, scribing out a large circle as the Earth completes one rotation.

  • Page 25: Latitude Scale

    DEC clutch knob and move the telescope so that the tube is parallel to the polar axis. When this is done, e declination setting circle will read +90°. If the declination setting circle is not aligned, move the telescope so that e tube is parallel to the polar axis.

  • Page 26: Finding The North Celestial Pole

    For example, in the northern hemisphere all stars move around the north celestial pole. When the telescope's polar axis is pointed at the celestial pole, it is pa to the Earth's rotational axis.

  • Page 27: Declination Drift Method Of Polar Alignment

    So, repeat the process again to improve the accuracy checking both es for minimal drift. Once the drift has been eliminated, the telescope is very accurately aligned. You can now do ime focus deep-sky astrophotography for long periods.

  • Page 28: Aligning The R.a. Setting Circle

    NOTE: Because the R.A. setting circle does NOT move as the telescope moves in R.A., the setting circle must be aligned each time you want to use it to find an object. This holds true even if you are using an optional motor drive.

  • Page 29: Using The R.a. Vernier Scale

    R.A. setting circle. Remember between the 18 h 50 m mark and the 19 h 0 5. Look through the telescope and the Ring Nebula should be within the field o power eyepiece (assuming you have already set the DEC).

  • Page 30: Celestial Observing

    With your telescope set up, you are ready to use it for observing. This section covers visual observing hints for both lar system and deep sky objects as well as general observing conditions which will affect your ability to observe.

  • Page 31: Observing The Sun

    Sun is so bright, special precautions must be taken when observing our star so as not to damage your eyes or your lescope. ever project an image of the Sun through the telescope. Because of the folded optical design, tremendous heat build- up will result inside the optical tube. This can damage the telescope and/or any accessories attached to the telescope.

  • Page 32: Seeing

    Filters are commonly used to bring ou t particular planetary detail, such as the polar caps on Mars or the bands and nes around Jupiter. The use of Celestron's Refractor Filter (# 94121) reduces the effect of chromatic aberration as well as improves contrast and re solution.

  • Page 33: Astrophotography

    The camera must have interchangeable lenses so you can attach it to the telescope and so you can use a varie lenses for piggyback photography. If you can't find a new camera, you can purchase a used camera body that 00-percent functional.

  • Page 34: Short Exposure Prime Focus Photography For Refractors & Newtonians

    Mount your camera body onto the T-Ring Use a T-Adapter ( # 93633-A) which threads on to the back of the telescope. The T-Ring threads onto the T-Adapter and then mount your camera body onto the T-Ring like you would any other lens.

  • Page 35: Eyepiece Projection For A Schmidt-Cassegrain

    Advance the film and card should be h eld a few inches in front of the telescope, and not touching it. It is easier if you use two people for this process; one to r elease the camera shutter and one to hold the card.

  • Page 36: Long Exposure Prime Focus Photography

    Most of these objects cover large angular areas and fit nicely into the prime focus field of your telescope. The brightn requires long exposure times and, as a result, are rather difficult.

  • Page 37: Planetary And Lunar Photography With Special Imagers

    For this purpose, Celestron offers the Micro Guide Eyepiece (# 94171) Here is a brief summary of the technique. Note: Digital Cameras – follow the camera instructions on foc Polar align the telescope. For more information on manual.

  • Page 38: Ccd Imaging For Deep Sky Objects

    Several books have been written on teleph oto lens for terrestrial (land) photography. Your telescope is in essence a R cameras are mounted directly to the telescope (using the built-in T- ersal Digital Camera Adapter (# 93626).

  • Page 39: Telescope Maintenance

    This will remove the moisture from the telescope tube. To minimize the need to clean your telescope, replace all lens covers once you have finished using it. Since the cells are NOT seale d, th e covers should be placed over the openings when not in use.

  • Page 40: Collimation Of A Schmidt-Cassegrain

    Pick a bright star and center it in the field of the telescope. Study the image of the star while racking it in and out of focus using an eyepiece that yields 30 to 60 power for every inch of aperture. If an unsymmetrical necessary.
  • Page 41 Before you begin the collimation process, be sure that your telescope is in thermal equilibrium with the surroundings. Allow 45 minutes for the telescope to reach equilibrium if you move between large temperature extremes. To verify collimation, view a star near the zenith. Use a medium to high power ocular — 12mm to 6mm focal length. It is important to center a star in the center of the field to judge collimation.

  • Page 42: Collimation Of A Newtonian

    Newtonian Coll ima on Tool (#94183) offered by Celestron. To collimate the telescope without the Collimation Tool, read the g section on night time star collimation. For very precise collimation, the optional Collimation Eyepiece followin 1 ¼”...

  • Page 44: Night Time Star Collimating

    The telescope should be set up at night and a star's image should be studied at medium to high power (30-60 power per inch of aperture). If a non-symmetrical focus pattern is present, then it may be possible to correct this by re-collimating only the primary mirror.
  • Page 45 IMPORTANT: After making the first, or each adjustment, it is necessary to re-aim the telescope tube to re center the star again in the center of the field of view. The star image can then be judged for symmetry by going just inside and outside of exact focus and noting the star's pattern.

  • Page 46: Optional Accessories

    Barlow Lens - A Barlow lens is a negative lens that increases the focal length of a telescope. Used with any eyepiece, it doubles the magnification of that eyepiece. Celestron offers two Barlow lens in the 1-1/4" size. The 2x Ultima Barlow (# 93506) is a compact triplet design that is fully multicoated for maximum light transmission and parfocal when used with the Ultima eyepieces.
  • Page 47 18%. Motor Drive, Dual Axis (# 93522) - This dual axis motor drive, with drive corrector capabilities, is designed for Celestron's Omni CG-4 mounts. It precisely controls the telescope's tracking speed during long, timed exposures of celestial objects, roducing the best possible image sharpness.
  • Page 48 Sky Map (# 93722) - Celestron Sky Maps are the ideal teaching guide for learning the night sky. You wouldn’t set off on a road trip without a road map, and you don’t need to try to navigate the night sky without a map either.

  • Page 49: Appendix A Technical Specifications

    Omni XLT Series ptical Design Aperture Focal Length Focal Ratio ptical Coatings indersc Star Diagonal Eyepiece – (std) MC 50deg FOV Mount - Equatorial T ripod Legs ounterweights Highest Useful Magnification Lowest Useful Magnification imiting Stellar Magnit Resolution: Raleigh -arc seconds...

  • Page 50: Appendix B - Glossary Of Terms

    Sun against the stars". Equatorial mount A telescope mounting in which the instrument is set upon an axis which is parallel to the axis of the Earth; the angle of the axis must be equal to the observer's latitude.
  • Page 51 Reflector A telescope in which the light is collected by means of a mirror. nd the point at which the image of an object at infinity is d by the aperture of the mirror or lens is termed the focal the light-year equals a distance of 9.46 X 1 trillion km (5.87 X 1...
  • Page 52 It was invented in 1930 by Bernhard Sidereal Rate This is the angular speed at which the Earth is rotating. Telescope tracking motors drive the telescope at this rate. The rate is 15 arc seconds per second or 15 degrees per hour. Terminator boundary Universe The totality of astronomical things, events, relations and energies capable of being described objectively.
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  • Page 59: Celestron Two Year Warranty

    Celestron, is found to be defective in materials or workmanship. As a condition to the obligation of Celestron to repair or replace such product, the product must be returned to Celestron together with proof-of-purchase satisfactory to Celestron.
  • Page 60 Celestron 5 Columbia Street Torr nce, CA 90503 U.S.A. Tel. (310) 328-9560 310) 212-5835 Web site at http//www.celestron.com Copy right 2007 Celestron All rights reserved. (Products or instructions may change with out notice or obligation.) tem # 21088-INST ted in China $10.00...

This manual is also suitable for:

Omni xlt 102Omni xlt 120Omni xlt 150Omni xlt 127

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