Celestron AstroMaster Telescope User Manual

Critical Safety Warnings ⚠️

NEVER look at the Sun directly with the naked eye or through the telescope (unless you have a specially designed solar filter). Such observation can lead to complete and irreversible loss of vision.

NEVER use the telescope for solar projection onto a screen. The heat accumulated in the optical system can damage the telescope and accessories.

NEVER use eyepiece solar filters or Herschel wedges. The large amount of heat focused at the focal point can damage the telescope. Furthermore, eyepiece filters can crack under heat, risking vision loss. The only safe way to observe the Sun is by using objective filters (e.g., Baader film).

Do not leave the telescope unattended in the presence of individuals unfamiliar with these safety rules.

Telescope Components

Diagram shows numbered parts:

• 1. Optical Tube
• 2. Star Pointer Finder
• 3. Eyepiece
• 4. Diagonal (90-degree)
• 5. Focus Knob
• 6. Handle
• 7. Tripod
• 8. Accessory Tray
• 9. Tripod Height Adjustment
• 10. Achromatic Objective Lens
• 11. Mounting Rail Socket
• 12. Azimuth Head

Telescope Assembly

Assemble the telescope for the first time at home to familiarize yourself with the parts. Assembly under the night sky can be more challenging.

Box Contents

Each AstroMaster telescope is delivered in one box containing:

• Optical tube with attached Star Pointer finder.
• Alt-azimuth mount with attached handle.
• 10mm 1.25" Eyepiece.
• 20mm 1.25" Eyepiece.
• 1.25" Diagonal.

You can also download the Starry Night sky learning software from www.celestron.com.

Tripod Setup

Diagram shows tripod unfolding and accessory tray installation.

1. Remove the tripod from the box. It comes pre-assembled.
2. Point the tripod legs downwards and extend them to their maximum height. Press the central spreader to unfold the legs outwards.
3. Install the accessory tray onto the leg spreader.
4. Place the accessory tray in the center of the spreader, aligning the cutouts with the mountings on the spreader.
5. Rotate the tray so its ends slide under the corresponding arms of the spreader. The tray should lock securely in place. The tripod is now fully assembled.
6. Tripod height can be adjusted from 61cm to 104cm. Loosen the handle screws on the legs, slide the legs to the desired position, and retighten the screws.
7. The tripod is most stable with the legs extended the least.

Aiming the Telescope

AstroMaster telescopes can be easily directed to any point in the sky.

• Vertical Adjustment (Altitude): Use the long, comfortable handle located on the mount head.
• Horizontal Adjustment (Azimuth): Use the same handle and a locking screw. The handle can rotate on its longitudinal axis. To lock the telescope's altitude, turn the handle counter-clockwise. Loosening the handle allows for smooth, delicate rotation.

Connecting the Tube to the Mount

The optical tube mounts onto the mount via a special guide using a "dovetail" rail. The rail is attached directly to the telescope tube. Ensure both axes are locked before mounting the optical tube.

Diagram shows inserting the dovetail rail into the mount head.

To mount the tube:

1. Remove any protective paper covering the telescope tube.
2. Loosen the large locking screw and the smaller safety screw (located at a 45-degree angle) in the guide. Ensure their tips do not protrude inside the guide.
3. Insert the mounting rail into the guide.
4. Tighten the locking screw to press the rail against the opposite edge of the guide, securing the tube.
5. Tighten the safety screw so its tip rests against the mounting rail.

Installing the Diagonal and Eyepieces

The included diagonal uses a glass prism to provide an upright, terrestrial image (mirror-reversed left-to-right). It also improves viewing comfort by allowing observation from the side, which is useful for high-altitude objects. The diagonal can be rotated to any comfortable position.

Installation procedure:

1. Insert the metal barrel of the diagonal into the 1.25" eyepiece holder. Ensure the two locking screws on the end of the holder are not screwed inwards. Tighten the screws after the diagonal is in place.
2. Insert the metal barrel of the eyepiece into the free end of the diagonal. Tighten the eyepiece locking screws.
3. Eyepieces can be replaced using the method described in step 2.

Focusing

To achieve a sharp image, turn the focus knobs located on the eyepiece holder. Turning clockwise focuses on more distant objects; turning counter-clockwise focuses on closer objects.

Note: If you wear corrective lenses (especially glasses), you may need to remove them for observation. Observing without glasses is generally more comfortable, and the necessary correction can be made using the focus knob. The only exception is astigmatism, which the telescope's optics cannot correct.

Using the StarPointer Finderscope

The StarPointer is a simple device for aiming the telescope. It projects a red illuminated dot into the field of view, similar to a laser pointer. It consists of two transparent plates with the illuminated dot, powered by LEDs, making it safe for the eyes. It uses a 3V CR1620 battery.

Alignment Procedure: The StarPointer must be aligned with the telescope's optical axis before first use. This is done using the adjustment screws on its edges. Alignment is best performed at night. During the day, the red dot may be difficult to see unless aimed at a dark object.

1. Turn on the StarPointer's illumination using the switch at its base.
2. Find a bright star or planet. Aim the telescope at it using the lowest magnification eyepiece and center the object in the field of view.
3. Look through the StarPointer window with both eyes. You should see the star. If the StarPointer is perfectly aligned, the red dot will precisely cover the star. If not, the star will appear next to the dot.
4. Use the two adjustment screws to position the red dot so it exactly covers the chosen star.
5. The StarPointer is now ready for use. Always turn it off after finding your object to significantly extend battery and LED life.

Diagram shows StarPointer controls: Elevation adjustment knob (Up/Down), Power switch (ON/OFF), Azimuth adjustment knob (Left/Right), Battery compartment.

Battery Installation: Your battery may already be installed. If not, it's supplied separately. Open the battery cover using a coin or screwdriver. Insert the battery with the positive (+) terminal facing inwards. It's a 3V CR1620 battery.

Image Orientation

Image orientation depends on the diagonal used. A 90-degree diagonal with a prism provides an upright image, but it is mirror-reversed (left-to-right). Viewing directly without a diagonal results in a completely inverted image. The prism diagonal supplied with AstroMaster refractors provides a correct, upright, terrestrial image.

Astronomical Guide

Key Optical Parameters

Aperture (Diameter): Generally, the larger the telescope's aperture, the better the images. A 130mm telescope will see much more than a 70mm one, and a 200mm telescope is a powerful instrument for observing distant galaxies.

Mount Types:

• Alt-azimuth Mount: Allows vertical (altitude) and horizontal (azimuth) movement. Convenient for nature observation, economical, durable, and reliable. Operation is simple and intuitive.
• Paralactic (Equatorial) Mount: One axis is aligned with Earth's axis. This allows tracking celestial objects by moving only one axis, matching their apparent motion across the sky. It's well-suited for sky observation but impractical for terrestrial viewing.

What Can You See?

Don't expect Hubble-quality colorful images of nebulae. Human eyes have limitations. However, even small telescopes clearly show lunar craters, planet disks, and Saturn's rings. A 130mm telescope can reveal cloud bands on Jupiter or polar caps on Mars. A 200mm telescope under dark skies can show spiral arms in the brightest galaxies.

Observing the Sun

Observing sunspots is easy with a solar filter made from AstroSolar film (by Baader Planetarium). Safety is paramount. The Sun is a powerful light source; unfiltered observation through a telescope or binoculars is dangerous and can cause permanent vision damage. Always use a front-mounted solar filter.

Calculating Magnification

Magnification = Telescope Focal Length / Eyepiece Focal Length.

Example: 800mm telescope focal length / 10mm eyepiece focal length = 80x magnification.

Practical Magnification Limit: Earth's atmosphere causes turbulence, degrading image sharpness at high magnifications. While telescopes are theoretically capable of very high magnifications, practical limits are often imposed by atmospheric conditions. A common guideline for maximum useful magnification is 2x the aperture diameter in millimeters for refractors and 1.5x for reflectors. For detailed planet observation, 150-200x is often sufficient.

Calculating Field of View (FOV)

True FOV = Eyepiece Apparent FOV / Magnification.

Example: 52° eyepiece FOV / 80x magnification = 0.65° (39 arcminutes). The Moon's diameter is about 0.5°.

Higher magnification results in a smaller FOV, making it harder to find objects. Start with lower magnifications.

Exit Pupil

The exit pupil is analogous to the human eye's pupil and affects image brightness and sharpness. The human pupil dilates to about 7mm in darkness. Exit Pupil = Telescope Aperture (mm) / Magnification.

Example: A 200mm f/5 telescope with a 30mm eyepiece gives 33x magnification and a 6mm exit pupil. A 25mm eyepiece (40x mag) gives a 5mm exit pupil, suitable for most adapted eyes. For planets, aim for ~1mm exit pupil; for nebulae and galaxies, 2-4mm is good.

Photography and Computer Connection

Most telescopes can be adapted for photography. Even inexpensive models allow lunar photography at higher magnifications than telephoto lenses. Mounts with precise drives enable nebulae photography with long exposures.

Cameras can connect via USB to a computer for observation on a monitor, image saving, and processing. Higher-quality 16-bit cameras are available for advanced users.

Magnification Myths and Color Vision

Beware of small telescopes advertised with extremely high magnifications (500x+); they produce poor quality images. The practical limit is around 2x aperture diameter (mm). Exceeding this results in dark, blurry images.

Maximum magnification is the highest that shows increased detail without significant quality loss. It's generally 2x aperture diameter (mm), but atmospheric conditions dictate the actual usable magnification.

Color is limited in visual observation. Only the brightest objects like planets and stars show distinct colors. Nebulae appear gray because the eye's light-sensitive rods are colorblind at low light levels. Mars appears orange; the Orion Nebula (M42) appears gray.

Sky Observations

Atmospheric Conditions

Seeing: Refers to atmospheric stability. Turbulence causes stars to twinkle or "boil." Good seeing means stable star images.

Transparency: Refers to air clarity. Water vapor or dust scatters light.

Choosing a Viewing Location

Ideal locations are far from artificial light pollution and air pollution. Higher elevations are better. Ensure a clear view, especially towards the south (in the Northern Hemisphere). The zenith offers the shortest path through the atmosphere. Avoid observing near buildings or trees that can cause air turbulence.

NEVER observe through windows or doors, as glass distorts images. Open windows can also cause turbulence from escaping warm air. Always observe outdoors.

Choosing a Viewing Time

Stable, clear air is best. Gaps between clouds can provide good viewing. Avoid observing immediately after sunset when the cooling ground causes air movement. Early morning hours are also good. Objects are best viewed when they cross the celestial meridian (highest point in the sky), minimizing atmospheric distortion. Observations near the horizon pass through a thicker, more polluted layer of atmosphere.

Telescope Cooling and Eye Adaptation

Telescope Cooling: Allow the telescope to reach ambient temperature before observing (approx. 2 minutes per cm of aperture) to minimize internal air currents. Use this time to align with Polaris.

Eye Adaptation: Protect your eyes from light (except red light) for about 30 minutes before observing to maximize pupil dilation. Observe with both eyes for comfort. For faint objects, use "averted vision" (looking slightly away from the object) as peripheral vision is more sensitive to low light.

What and How to Observe

Aim for specific targets. Randomly pointing the telescope may yield nothing interesting, especially under light-polluted skies.

The Moon

The Moon is an excellent first target. Its details are visible in any telescope. Use the lowest magnification eyepiece (e.g., 25mm) to find it, then switch to higher magnifications to observe details. Craters are most dramatic near the terminator (the line between light and dark). First and last quarter phases are best for observing craters due to long shadows. The full Moon is less detailed due to the lack of shadows. Earthshine (light on the dark side) is visible a few days before/after the new moon. A Moon filter reduces brightness and improves comfort.

Planets

• Mercury: Closest to the Sun, difficult to observe. Visible shortly after sunset or before sunrise. Use colored filters (red, orange, yellow) to improve contrast. Shows phases.
• Venus: The brightest planet. Shows phases like the Moon. Its apparent size changes significantly with its phase. Use short focal length eyepieces and polarizing filters.
• Mars: The "Red Planet." Visible details and polar caps are seen when it's close to Earth. Use high magnification and colored filters (green for polar caps, orange for surface features) to enhance contrast.
• Jupiter: Shows distinct bands and its four largest moons (Galilean moons). Larger telescopes may reveal the Great Red Spot and finer band details. Moon shadows can be seen crossing Jupiter's disk.
• Saturn: Visible rings are seen even in small telescopes as "ears." Larger telescopes reveal the rings distinctly, and potentially the Cassini Division. Titan, its largest moon, is visible.
• Uranus & Neptune: Gas giants, distant and difficult to observe. Uranus appears as a small, grayish disk. Neptune is even fainter and harder to spot.
• Pluto: A dwarf planet, visible only in larger telescopes with precise star charts, appearing as a very faint star.

Deep Sky Objects (DSOs)

Most DSOs require dark skies away from city lights.

• Open Clusters: Often spectacular. Examples: Chi and H Persei.
• Globular Clusters: Millions of stars. Examples: M13, M3, M5, M92, M15. Larger telescopes resolve individual stars on the cluster edges.
• Nebulae (Emission & Reflection): Large, subtle objects. Require dark skies and low magnification. Orion Nebula (M42) is an exception. Nebulae filters (e.g., Baader UHC-S) improve contrast and visibility.
• Galaxies: Distant star systems. Nearest is Andromeda (M31). Requires wide field of view. M51 (Whirlpool Galaxy) shows its spiral structure in medium telescopes.
• Planetary Nebulae: Star remnants. Often small and require high magnification. M57 (Ring Nebula) appears as a small disk or ring.

Beginner Tips:

• Most objects appear gray due to low-light color vision limitations.
• Stars appear as points; telescopes reveal fainter ones.
• Always start with the longest focal length eyepiece (lowest magnification) to find objects, then increase magnification.
• Telescopes are robust; problems are usually finding objects or using too high magnification.

Equipping Your Telescope

You may wish to expand your setup with additional accessories.

Eyepieces

Eyepieces are crucial for image quality. They are characterized by focal length (magnification), apparent field of view (FOV), optical design, barrel size (1.25" or 2"), and eye relief (comfort).

Common designs include Kellner, Orthoscopic, Plössl, and Lanthanum eyepieces, each offering different performance characteristics and FOV.

Barlow Lenses

A Barlow lens multiplies the magnification of any eyepiece by 2x, 2.5x, 3x, 4x, or 5x. This effectively doubles your usable magnification range, though it reduces image brightness and FOV.

Filters

Filters screw into eyepieces to improve image quality. They include nebulae filters (to enhance faint DSOs by blocking light pollution) and color filters (for planetary observation to increase contrast).

Maintenance

Telescope Cleaning

Protect optics from dirt. Clean only when necessary.

• Refractor Objectives: Use a microfiber cloth and lens cleaning fluid. Remove dust first with a soft brush or blower bulb to prevent scratching.
• Newtonian Mirrors: Clean gently with a soft brush or compressed air for dust. Use fluid and cloth for stubborn dirt. Collimation is required after cleaning.
• Eyepieces: Use a brush for dust. Clean lenses with a soft pad or cloth and fluid (do not spray directly). Do not disassemble eyepieces.

Collimation

Collimation is the process of aligning optical surfaces. Newtonians are sensitive to it. Laser collimators are the most convenient tool. Adjust the secondary mirror first to center the laser beam on the primary mirror, then adjust the primary mirror to send the beam back to the center of the collimator's screen.

Simple Astrophotography

Afocal Projection: Attach a camera (even a smartphone) behind the eyepiece. Use a camera adapter for stability. Image quality is limited by the camera's optics.

Eyepiece Projection: Use a camera without its lens, or a CCD camera, placed behind the eyepiece. The effective focal length can be adjusted by changing the distance between the eyepiece and the camera sensor. This method allows high magnification but can suffer from vignetting.

Important Notes

Final Safety Reminder: NEVER look at the Sun directly through the telescope. Use only a front-mounted solar filter. Cover or remove the finder scope during solar observation. Never use an eyepiece solar filter or project the Sun's image onto a surface, as heat will damage the telescope.

Accessories Overview

Lens Pen (Catalog No: 93575): For cleaning optics.

Moon Filter 1.25" (Catalog No: SW-5600): Reduces moon brightness, increases contrast.

Rotating Star Chart (Catalog No: DO-6800): Essential for beginners to identify constellations and objects.

First Astronomical Observations (Catalog No: DO-6803): Beginner-friendly guide.

Medium Cover (Catalog No: DO-6921): For telescope transport and storage (fits AstroMaster 70AZ, 90AZ).

Color Filters: For observing Solar System objects (green, light red, dark blue).

Accessory Kit for AstroMaster Telescopes (Catalog No: 94307): Includes eyepieces, Barlow lens, filters, microfiber cloth.

Importer: Delta Optical G.Matosek, H.Matosek Sp.j. Nowe Osiny, ul. Piłkna 1, 05-300 Mińsk Mazowiecki, Poland www.deltaoptical.pl