Celestron AstroMaster Series Telescopes

Introduction

Congratulations on your purchase of an AstroMaster Series telescope. This manual covers two models: the 90mm refractor and the 130mm Newtonian, both mounted on the CG-3 German Equatorial Mount. The AstroMaster Series is built with high-quality materials for stability and durability, offering a lifetime of astronomical pleasure with minimal maintenance.

Designed for first-time buyers, these telescopes offer exceptional value with a compact, portable design and ample optical performance to introduce newcomers to amateur astronomy.

AstroMaster telescopes come with a two-year limited warranty. For details, visit www.celestron.com.

Standard Features:

• All coated glass optical elements for clear, crisp images.
• Smooth, rigid equatorial mount with setting circles in both axes.
• Preassembled steel leg tripod with 1.25" legs for a stable platform.
• Quick and easy no-tool setup.
• Includes "The Sky" Level 1 astronomy software CD-ROM for sky education and printable maps.
• All models can be used terrestrially as well as astronomically with included accessories.

Read this manual thoroughly before your first observing session to familiarize yourself with the telescope's operation. This manual provides detailed information, reference material, and helpful hints for an enjoyable observing experience.

Warning

• Never look directly at the sun with the naked eye or telescope (unless using a proper solar filter). Permanent eye damage may result.
• Never use the telescope to project an image of the sun onto any surface. Internal heat can damage the telescope and accessories.
• Never use an eyepiece solar filter or Herschel wedge. Internal heat can cause them to crack or break, allowing unfiltered sunlight.
• Do not leave the telescope unsupervised, especially with children or individuals unfamiliar with its operation.

Assembly

Set up your telescope indoors first to easily identify parts and learn the assembly procedure before going outdoors.

Each AstroMaster package includes: optical tube with attached sky pointer and tube rings (130 EQ only), CG-3 equatorial mount, counterweight bar, two 3.7 lb (1.7kg) counterweights, R.A. & Dec. slow-motion cables, a 10mm eyepiece (1.25"), a 20mm eyepiece (1.25", erect image for 130EQ), an erect image diagonal (1.25" for 90EQ), and "The Sky" Level 1 CD-ROM.

Setting up the Tripod

1. Remove the tripod from the box. It comes preassembled for easy setup.
2. Stand the tripod upright, pull the legs apart until fully extended, and push down slightly on the leg brace. The top of the tripod is the tripod head.
3. Install the tripod accessory tray onto the tripod leg brace.
4. Insert the tray's cut-out (flat side down) into the center of the tripod leg brace and push down. The tray's ears should align as shown in the diagram.
5. Rotate the tray until its ears lock under the leg brace support of each leg. The tripod is now assembled.
6. Extend the tripod legs to your desired height. The height ranges from 24" (61cm) to 41" (104cm). Unlock the leg lock knob at the bottom of each leg, extend, and then securely lock the knob.
7. The tripod is most rigid and stable at its lowest height.

Diagram Description: Figures 2-1 through 2-8 illustrate the tripod setup process, showing the tripod, its leg brace, the accessory tray, and the locking mechanism for extending the legs.

Attaching the Equatorial Mount

The equatorial mount allows you to tilt the telescope's axis of rotation to track stars. The AstroMaster uses a German equatorial mount (CG-3).

1. Remove the equatorial mount from the box. It will have a small latitude adjustment screw attached. The large latitude adjustment screw is threaded into its hole.
2. Align the mount with the tripod head's knob with bolt. Push the mount's flat portion into the center hole of the tripod head until flush.
3. Reach under the tripod head and turn the knob to thread it into the bottom of the mount until tight. The completed assembly is shown in the diagram.

Diagram Description: Figures 2-9, 2-10, and 2-11 show the equatorial mount, its latitude adjustment screw, and how it attaches to the tripod head.

Installing the Counterweight Bar & Counterweights

Proper balance is achieved with the counterweight bar and two counterweights.

1. Remove the counterweight safety screw (orange) from the counterweight bar by unthreading it counterclockwise.
2. Install the counterweight bar's large threads into the mount's dec.axis hole until tight.
3. Orient the mount so the counterweight bar points downward.
4. Loosen the locking knob on each counterweight so the threads do not protrude through the center hole.
5. Slide one counterweight onto the bar about halfway and tighten its locking knob.
6. Slide the second counterweight onto the bar flush against the first and lock it securely.
7. Replace and securely thread the safety screw.

Diagram Description: Figures 2-12, 2-13, and 2-14 illustrate the counterweight bar, its safety screw, and the counterweights being attached to the mount.

Attaching the Slow Motion Cables

Two slow motion control cables are provided for fine pointing adjustments in R.A. and Declination.

1. Locate the two cables with knobs. Ensure the screw on each cable end does not protrude.
2. Slide one cable onto an R.A. shaft (either side works). Tighten the screw to secure it.
3. The DEC slow motion cable attaches similarly to the R.A. shaft, located near the top of the mount.

Diagram Description: Figures 2-15 and 2-16 show the R.A. and Dec. shafts on the mount and the slow motion cables with their knobs attached.

Attaching the Telescope Tube to the Mount

The telescope tube attaches via a dovetail slide bar mounting bracket.

1. Remove protective paper from the optical tube. (For 114EQ Newtonian, remove tube rings first.)
2. Loosen the mounting knob and safety screw on the dovetail mounting platform so they do not protrude.
3. Slide the dovetail mounting bar into the recess on the mounting platform.
4. Tighten the mounting knob to secure the telescope.
5. Hand-tighten the mounting platform safety screw until its tip touches the bracket.

Note: Only loosen R.A. and DEC knobs on the telescope tube or mount.

Diagram Description: Figures 2-17 and 2-18 show close-ups of the mount's lock knobs and the dovetail mounting platform with its knob and safety screw.

Installing the Diagonal & Eyepieces (refractor)

The diagonal diverts light at a right angle for more comfortable viewing and corrects the image to be right-side-up and left-to-right correct. It can be rotated for optimal positioning.

1. Insert the diagonal's small barrel into the 1.25" eyepiece adapter of the refractor's focuser. Ensure thumbscrews do not protrude into the focuser tube. Remove the plug cap from the adapter.
2. Insert an eyepiece into the diagonal and tighten the thumbscrew, ensuring it doesn't protrude into the diagonal.
3. Eyepieces can be changed by reversing this procedure.

Diagram Description: Figure 2-19 shows the diagonal being inserted into the focuser tube of a refractor telescope.

Installing the Eyepieces on the Newtonians

Eyepieces magnify the image. Longer focal length eyepieces provide lower magnification.

1. Ensure focuser thumbscrews are not protruding. Remove the focuser's plug cap.
2. Insert the eyepiece's chrome barrel into the focuser tube and tighten the thumbscrews.
3. The 20mm eyepiece is an erecting eyepiece, providing a right-side-up and left-to-right correct image, useful for terrestrial viewing.
4. Eyepieces can be changed by reversing this procedure.

Diagram Description: Figure 2-20 shows an eyepiece being inserted into the focuser tube of a Newtonian telescope.

Telescope Basics

Telescopes collect and focus light. Refractors use lenses, while reflectors (Newtonians) use mirrors.

The refractor, developed in the 1600s, uses a lens to bend light. Early single-element lenses caused chromatic aberration (color fringing). Achromat lenses, with two elements, correct this by focusing different wavelengths of light at the same point.

The Newtonian reflector uses a concave primary mirror at the back of the tube. Light is directed to a focal point. A flat secondary mirror intercepts the light and directs it out the side of the tube to the eyepiece for easier viewing. Newtonian reflectors offer more light-gathering power for their cost, allowing for longer focal lengths in a compact design. They require more care due to the exposed primary mirror.

Diagram Description: Figure 3-1 illustrates the light path in a refractor telescope, showing light passing through a lens. Figure 3-2 illustrates the light path in a Newtonian telescope, showing light reflecting off two mirrors before exiting the focuser.

Image Orientation

Image orientation depends on the eyepiece setup. With a refractor and erect image diagonal, the image is right-side-up and correctly oriented left-to-right. Without the diagonal, the image is inverted. Newtonian reflectors produce a right-side-up image that may be rotated; the supplied erect image eyepiece corrects this.

Diagram Description: Figure 3-3 shows three license plates demonstrating different image orientations: normal, reversed left-to-right (as with a refractor's star diagonal), and inverted (as with a refractor's eyepiece directly in the focuser or a Newtonian without an erecting eyepiece).

Focusing

To focus, turn the focus knob below the eyepiece holder. Clockwise moves focus for distant objects; counterclockwise for closer objects.

Note: Remove glasses if you wear them for observing. Always wear corrective lenses when using a camera for sharp focus. If you have astigmatism, wear corrective lenses at all times.

Aligning the Finderscope

The Star Pointer finderscope is a zero-magnification tool that projects a red dot onto the night sky, aiding in pointing the telescope. It uses a coated glass window and an LED.

To align the Star Pointer:

1. Turn the Star Pointer switch to the "on" position.
2. Center a bright star or planet in a low-power eyepiece of the main telescope.
3. Look through the Star Pointer's window with both eyes open. The red dot should overlap the star.
4. If misaligned, adjust the Star Pointer's screws until the red dot is directly over the star.
5. Turn the Star Pointer off after finding an object to conserve battery life.

Note: The battery is usually pre-installed. If not, open the compartment with a coin or screwdriver and insert a 3-volt lithium battery (#CR1620) with the '+' sign facing out.

Diagram Description: Figure 3-4 shows the Star Pointer with its battery compartment and switch. Figure 3-5 is a close-up of the Star Pointer lens.

Calculating Magnification

Magnification = Focal Length of Telescope (mm) / Focal Length of Eyepiece (mm).

For example, using a 20mm eyepiece with a 1000mm focal length telescope yields 50x magnification (1000mm / 20mm = 50x).

The highest useful magnification is generally limited by aperture. A rule of thumb is 60x per inch of aperture. For the AstroMaster 90EQ (3.5" aperture), this is 210x. Most observing is done at 20-35x per inch.

Determining Field of View

True Field = Apparent Field of Eyepiece / Magnification.

Using the previous example (50x magnification, 50° apparent field of view), the true field is 1.0° (50° / 50x = 1.0°). To convert degrees to feet at 1,000 yards, multiply by 52.5 (1.0° x 52.5 = 53 feet).

General Observing Hints

• Never look through window glass, as its imperfections can affect focus and cause double images.
• Avoid observing over objects producing heat waves (e.g., asphalt, rooftops) as they distort images.
• Hazy skies, fog, or mist reduce detail, especially for terrestrial viewing.
• If wearing corrective lenses (glasses), remove them for eyepiece viewing. Always wear them for camera use to ensure sharp focus. If you have astigmatism, wear them at all times.

Astronomy Basics

To understand your telescope better, this section covers observational astronomy, the night sky, and polar alignment.

The Celestial Coordinate System

Astronomers use a celestial coordinate system similar to Earth's geographical system, with poles, lines of longitude (Right Ascension - R.A.), and latitude (Declination - DEC), and an equator.

• Declination (DEC): Similar to Earth's latitude, measured in degrees north (+) or south (-) of the celestial equator.
• Right Ascension (R.A.): Similar to Earth's longitude, measured in hours, minutes, and seconds, starting from a point in Pisces (0 hours).

Diagram Description: Figure 4-1 shows the celestial sphere, illustrating the celestial equator, poles, and lines of R.A. and DEC.

Motion of the Stars

The apparent daily motion of the Sun and stars is due to Earth's rotation. Stars near the celestial equator form the largest circles, rising in the east and setting in the west. Stars closer to the celestial poles form smaller circles. Circumpolar stars are always visible, never rising or setting. Timed exposures can reveal these circular paths.

Polar Alignment with Latitude Scale

Polar alignment makes the telescope's axis of rotation parallel to Earth's axis for accurate tracking. This is achieved by adjusting the mount's altitude.

To align using the latitude scale:

1. Point the mount's polar axis due north (use a landmark).
2. Level the tripod.
3. Adjust the mount in altitude until the latitude indicator matches your geographic latitude. This sets the angle of the polar axis.

This method can be done in daylight and helps limit tracking corrections.

Diagram Description: Figure 4-3 shows a close-up of the mount's latitude adjustment mechanism.

Pointing at Polaris

Polaris (the North Star) is very close to the North Celestial Pole. Pointing the telescope's polar axis at Polaris provides alignment within one degree. This must be done at night.

1. Set the polar axis pointing north.
2. Loosen the Dec. clutch knob and align the telescope tube parallel to the polar axis (Declination setting circle should read +90°).
3. Adjust mount altitude and azimuth until Polaris is visible in the finder.

Remember: Do not move the telescope itself, only the polar axis. The telescope is used to view the direction of the polar axis.

Finding the North Celestial Pole

In the northern hemisphere, Polaris is the end star in the Little Dipper's handle. The Big Dipper's pointer stars can help locate Polaris if the Little Dipper is hard to find. Cassiopeia is on the opposite side of the pole.

Diagram Description: Figure 4-4 shows the changing position of the Big Dipper. Figure 4-5 shows the Big Dipper, Little Dipper, Polaris, and Cassiopeia, indicating the North Celestial Pole (N.C.P.).

Aligning the Setting Circles

Setting circles help find objects using their celestial coordinates. The R.A. circle needs alignment.

To align the R.A. setting circle:

1. Locate a bright star near the celestial equator.
2. Center the star in the finderscope, then in the main telescope.
3. Look up the star's coordinates.
4. Rotate the R.A. setting circle until the correct coordinate aligns with the R.A. indicator.

Note: The R.A. setting circle does not move with the telescope's R.A. movement, so it must be aligned each time you use it, or you can use the coordinates of an object you are currently observing.

To find an object using aligned circles:

1. Select an object and look up its coordinates.
2. Move the telescope in Declination until the indicator matches the object's DEC coordinate. Lock the Dec. knob.
3. Move the telescope in R.A. until the indicator matches the object's R.A. coordinate. Lock the R.A. knob.
4. Center the object in the finderscope, then view it in the main optics.

Diagram Description: Figure 4-6 illustrates aligning the equatorial mount to the polar axis. Figure 4-7 shows close-ups of the R.A. and Dec. setting circles.

Celestial Observing

This section provides tips for observing solar system and deep sky objects, and discusses observing conditions.

Observing the Moon

Full moon is bright but offers little contrast. Partial phases (first or third quarter) reveal more detail due to long shadows. Use higher magnification eyepieces for closer views.

Lunar Observing Hints: Yellow filters improve contrast; neutral density or polarizing filters reduce brightness and glare.

Observing the Planets

Observe Venus's phases, Mars's surface and polar caps, Jupiter's cloud belts and Red Spot, and Saturn's rings. You can also see Jupiter's moons.

Planetary Observing Hints: Atmospheric conditions are key. Avoid observing planets low on the horizon or over heat sources. Celestron eyepiece filters can enhance planetary detail.

Observing the Sun

Solar observation is rewarding but requires caution. Use a solar filter to reduce the Sun's intensity and view sunspots and faculae.

• Best times are early morning or late afternoon when the air is cooler.
• To center the Sun without looking through the eyepiece, watch the telescope tube's shadow until it forms a circle.

Observing Deep Sky Objects

Deep-sky objects include star clusters, nebulae, galaxies, etc. They are often faint and best viewed under dark skies. Light pollution reduces contrast and makes nebulae difficult to see. Light Pollution Reduction (LPR) filters can help.

Seeing Conditions

Viewing conditions affect image quality and include transparency, sky illumination, and seeing (atmospheric stability).

• Transparency: Clarity of the atmosphere, affected by clouds and particles. Hazy skies reduce contrast.
• Sky Illumination: Moon, airglow, and light pollution reduce contrast for deep sky objects.
• Seeing: Atmospheric turbulence bends light, causing blurred images. Good seeing provides sharp detail; poor seeing results in blurred stars and objects.

Diagram Description: Figure 5-1 shows drawings illustrating different seeing conditions, from poor (blurred star) to excellent (sharp star).

Astrophotography

The AstroMaster series is designed for visual observing, but can be used for photography.

You will need a digital camera or 35mm SLR camera. Use a Universal Digital Camera Adapter (#93626) for digital cameras or a T-Ring and T-Adapter (#93625) for SLR cameras.

Short Exposure Prime Focus Photography

Attach your camera to the telescope. Polar align and use the optional motor drive for tracking. Image the Moon and planets, experimenting with settings and exposure times. Photograph from a dark sky site.

Piggyback Photography

(130EQ models only) Attach your camera with its normal lens on top of the telescope to capture constellations or large nebulae. Polar align and use the motor drive for tracking.

Diagram Description: Figure 6-1 shows a camera mounted piggyback on a telescope.

Planetary & Lunar Photography with Special Imagers

Special cameras like Celestron's NexImage (#93712) simplify capturing detailed planetary and lunar images.

CCD Imaging for Deep Sky Objects

Specialized CCD cameras allow amateurs to capture fantastic deep sky images, with technology continually improving.

Terrestrial Photography

Your telescope can serve as an excellent telephoto lens for terrestrial photography of landscapes, wildlife, and nature. Experiment with focus and settings.

Telescope Maintenance

Proper maintenance ensures optimal performance.

Care and Cleaning of the Optics

Dust or moisture may accumulate on lenses or mirrors. Clean with care to avoid damage.

• For dust, use a brush or pressurized air. Then, use an optical cleaning solution and soft tissue, wiping from the center outwards. Do not rub in circles.
• Cleaning solutions can be commercial or a mix of isopropyl alcohol and distilled water (60:40 ratio), or diluted dish soap.
• For dew, use a hairdryer on low setting or point the telescope downwards until it evaporates.
• If moisture condenses inside, remove accessories and point the telescope down in a dust-free environment.
• Always replace lens covers when not in use to prevent dust entry.

Internal adjustments and cleaning should only be performed by Celestron repair services.

Collimation of a Newtonian

Collimation (aligning optics) optimizes performance and corrects aberrations. It involves adjusting the primary and secondary mirrors.

Aligning the Secondary Mirror: Use the optional Newtonian Collimation Tool (#94183) or Collimation Eyepiece (#94182). Rack the focuser in completely. Look through the focuser at the secondary mirror's reflection of the primary mirror. Adjust secondary mirror screws to center the primary mirror's periphery in the view. Do not adjust the center screw of the secondary mirror support.

Diagram Description: Diagrams show views through the focuser during secondary mirror alignment, illustrating concentric mirror reflections. Figure 7-1 shows the rear cell of a Newtonian with collimation screws.

Night Time Star Collimating

After daytime collimation, fine-tune using a bright star at medium to high power (30-60x per inch of aperture).

Procedure:

1. Point at a stationary star like Polaris.
2. Locate collimation screws on the rear cell of the telescope tube. Loosen the small locking screws.
3. Turn one large collimation screw at a time, observing the star's image in the focuser. Adjust until the star appears as a sharp pinpoint.
4. If the star image flares or is irregular, adjust screws to move the image towards the flare direction.
5. Tighten the small locking screws when satisfied.

IMPORTANT: Re-aim the telescope after each adjustment. The star image should appear symmetrical. It may take adjusting two screws simultaneously.

Diagram Description: Figure 7-2 shows examples of star patterns indicating collimation status. Figure 7-3 shows a correctly collimated star pattern.

Optional Accessories

Enhance your viewing experience with these accessories:

• Sky Maps (#93722): Guide for learning the night sky.
• Omni Plossl Eyepieces: Economical eyepieces offering sharp views in various focal lengths (4mm to 40mm).
• Omni Barlow Lens (93326): Doubles magnification.
• Moon Filter (#94119-A): Reduces moon brightness and improves contrast.
• UHC/LPR Filter (#94123): Enhances deep sky viewing from light-polluted areas.
• Flashlight, Night Vision (#93588): Red LED flashlight to preserve night vision.
• Collimation Tool (#94183): For Newtonian collimation.
• Collimation Eyepiece (1.25", #94182): For precise Newtonian collimation.
• Digital Camera Adapter (Universal #93626): For afocal photography with digital cameras.
• T-Adapter (Universal 1.25", #93625): For attaching 35mm SLR cameras.
• Motor Drive: Compensates for Earth's rotation for smoother tracking.

AstroMaster Specifications

Note: Specifications are subject to change without notice or obligation.

Contact Information

Celestron
2835 Columbia Street
Torrance, CA 90503 U.S.A.
Tel: (310) 328-9560
Fax: (310) 212-5835
Website: www.celestron.com

Copyright 2007 Celestron. All rights reserved.

(Products or instructions may change without notice or obligation.)

Item #: 21064-INST
Printed in China