AstroMaster 70 EQ, 2.8" Equatorial refractor

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The Celestron 70mm AstroMaster equatorial refractor is a very sensibly-priced alternative to a 60mm “toy store” telescope for the beginning astronomer on a budget. It provides you with detailed high-contrast views of the Moon and planets within the solar system, as well as sharp views of binary stars, star clusters, and the brighter nebulas and galaxies outside the solar system.

The AstroMaster 70 has a light grasp 100 times that of the sharpest eye. It can resolve details ten times smaller than you can see clearly with your unaided eye. Combine that light grasp and sharpness with its two eyepieces (a 20mm for 45x magnification and a 10mm for 90x), and you have the ability to see many, many celestial objects and details that are simply invisible to the unaided eye. Some chromatic aberration (a faint halo of violet light around the Moon and planets when observing at night) is visible in the AstroMaster 70, as it is in all achromatic refractor telescopes.

The scope’s rugged and stable CG-2 equatorial mount has manual slow motion controls in both axes. These let you easily locate solar system and deep space objects and manually track them across the sky. The complete AstroMaster 70 EQ comes in a package that weighs only 18 lbs. It’s a telescope you can pick up and carry outside with one hand – a scope almost any young astronomer can set up on their own.

This Telescope’s Optical System . . .

  • Refractor optical tube: 70mm (2.8”) aperture. 900mm focal length f/12.9 achromatic doublet lens with all-glass optics. No plastic lenses.

  • Coated optics: Each air-to-glass surface of the two-element objective lens has a layer of magnesium fluoride antireflection coatings for high light transmission and good contrast.

  • Dovetail mount: A quick-release dovetail bar on the optical tube fits into a dovetail slot on the mount. The optical tube can be installed and locked firmly in place in seconds using a single no-tool knob on the mount.

  • Dew shield: A dew shield (an extension of the optical tube that’s threaded onto the front of the objective lens) slows the formation of dew on the lens in cold weather. This extends your undisturbed observing time. It also improves the contrast when observing objects on the ground during the day.

  • Rack and pinion focuser: The well-made 1.25” focuser has dual focusing knobs for precise image control with either hand. The good-sized focus knobs are easy to operate, even while wearing gloves or mittens in cold weather.

  • Star diagonal: The 90° viewing angle 1.25” star diagonal (eyepiece holder) allows comfortable viewing when looking overhead at the sky. It provides erect mirror image views (objects are reversed left for right).

  • Two eyepieces: You get a high power 1.25” 10mm (90x) eyepiece and a low power 1.25” 20mm (45x) with a 1.1° field of view (over twice the diameter of the full Moon). Both eyepieces have antireflection coatings on their lens surfaces for sharp images and good contrast.

  • Red dot finder: A straight-through red dot illuminated finder allows easy non-magnified views of the sky and ground, with a projected red dot of light showing exactly where the scope is pointed at all times.

This Telescope’s Mount . . .

  • Equatorial mount: The AstroMaster’s sturdy CG-2 equatorial mount is designed for astronomical observing. By aligning the mount on the north celestial pole, you only need to turn one slow motion control knob to follow planets and stars as they travel across the sky. Two counterweights on the opposite side of the mount from the telescope balance the weight of the optical tube and make it easy to move the scope effortlessly from one part of the sky to another. No tools are required to adjust the position of the counterweights to quickly and precisely balance the optical tube. A micrometer control lets you adjust the altitude of the scope mount for fast alignment on the north celestial pole with no tools required.

  • Dovetail tube mount: The optical tube is fitted with a dovetail slide bar that fits into a quick-release dovetail groove on the top of the mount. Installing the optical tube on the mount is quick and easy, even in the dark. The optical tube locks securely in place with no tools needed.

  • Setting circles: Setting circles (graduated scales marked in either hours and minutes or degrees) are provided in both right ascension (the east/west position of objects in the sky measured in hours and minutes) and declination (the north/south position measured in degrees). These allow you to align the scope on the approximate position of an object in the sky by using its r. a. and dec coordinates from a star chart – before you search for it in the red dot finder and eyepiece. Setting circles can reduce the time it takes for you to find the fainter and more difficult deep space objects.

  • Manual slow motion controls: There are two slow motion control knobs conveniently positioned on the mount so they are easy to reach while observing. One controls the scope’s motion in right ascension (the east/west direction in the sky). Turning this knob enables you to follow the motion of celestial objects as they travel from east to west across the heavens. The second controls the scope’s motion in declination (the north/south direction in the sky). Turning this knob enables you to correct for any north/south drift a celestial object may take as it drifts across the sky, due to an improper alignment of the scope on the north celestial pole when you first set it up. The two controls combine to give you complete access to any part of the sky. They give you the ability to star hop from a known object to any other object by using a star chart. They let you center objects in the field of view, and track them effortlessly with only an occasional quick turn of the r. a. knob.

  • Tripod: The very rigid tripod has 1.25” diameter stainless steel legs for vibration-free observing. The legs easily adjust in length to put the eyepiece at the most comfortable height for virtually any observer, young or old. The no-tool lock knobs that adjust the leg height of the tripod are on the inside of the legs so they won’t snag on clothing in the dark, a thoughtful touch that’s sure to be appreciated. The tripod includes an accessory shelf with cutouts to hold three eyepieces. A lip on the shelf keeps accessories from falling off during use.

  • Software: The scope comes with TheSky Level 1 sky-charting CD-ROM that has a database of 10,000 stars and objects it can plot and display on your Windows-based computer screen. That’s enough solar system and deep space detail to keep you busy observing for years, yet not so much that you’re overwhelmed by charts showing much more detail than your scope can usefully reveal. Custom sky chart printing lets you print out eyepiece finder charts to use with your telescope to help you locate and identify the planets and many famous and faint deep space nebulas, galaxies, and star clusters by star-hopping from object to object using your scope’s pan handle control. There are 75 full color images of well-known celestial objects to help you identify them through your scope.

  • Two year warranty: As an expression of Celestron’s confidence in the quality of their products, the AstroMaster is protected by Celestron’s two-year limited warranty against flaws in materials and workmanship.
Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
150x
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

11.7
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

900mm
Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

f/12.9
Resolution:
This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.65 arc seconds
Aperture:
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
2.8"
Weight:
The weight of this product.
18 lbs.
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
Refractor
 
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
No
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Good
Planetary Observation:
Fair
Binary and Star Cluster Observation:
Fair
Galaxy and Nebula Observation:
Fair
Photography:
Yes
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
No
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Yes
Planetary Photography:
No
Star Cluster / Nebula / Galaxy Photography:
No
Warranty:
2 years
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  • 70mm aperture achromatic refractor optical tube with 1.25” rack and pinion focuser
  • CG2 equatorial mount with dovetail bar quick release tube mount system, altitude adjustment micrometer control, setting circles, manual slow-motion controls, and locks on both axes
  • 10mm (90X) and 9 20mm (45X) eyepieces
  • Non-magnifying straight-through red dot finder
  • Adjustable height stainless steel tripod with accessory tray
  • Operating instructions
  • TheSky Level 1 CD-ROM star-charting software.
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Celestron - AstroMaster 70 EQ, 2.8" Equatorial refractor

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Celestron - AstroMaster 70 EQ, 2.8" Equatorial refractorFull-length image of scope on tripod.Close-up of the mount showing counterweights, slow motion controls, altitude adjustment for polar alignment, setting circles, and dovetail mount.Close-up of the red dot finderr, focuser, star diagonal, and eyepiece.
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Our Product #: AM70E
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For no more than the price of a “toy store” 60mm telescope, the AstroMaster 70 EQ equatorial refractor provides you with enough crisp and detailed images of the Moon, the planets, and many of the brighter deep space objects to keep you happily observing for years to come . . .





. . . our 34th year