Orion Observer 90mm Equatorial Refractor Telescope

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Orion Observer 90mm Equatorial Refractor Telescope

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This wonderfully capable equatorial refractor telescope gives beginning stargazers an exciting look at solar system favorites and beyond
Its 90mm (3.5") lens optics and 900mm focal length excel for stunning views of the lunar surface, Saturn's rings, and bright deep-sky gems like Great Hercules Cluster
The sturdy EQ3-class equatorial mount and aluminum tripod is a big upgrade from the mounts that comparable telescopes on the market come with
Two quality 1.25" Plossl eyepieces are included: a 25mm for low-power views at 36x, and a 10mm for getting in tight at 90x
Highly portable: the optical tube can be removed from the mount quickly via the dovetail mounting system and carried separately.

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Item # 52988b

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Beginning skywatchers looking for a low maintenance telescope that can serve up vivid, sharp images of the Moon, planets, and brighter deep-space objects need look no further than the Orion Observer 90mm Equatorial Refractor Telescope. A great telescope for the whole family, the Observer 90 EQ's fully antireflection coated 90mm-diameter (3.5") front lens boasts strong magnifying power. With the included 25mm and 10mm Plossl eyepieces you will view distant worlds in high-contrast detail at 36x and 90x! Jupiter's cloud bands are easily discerned, as are all four of its major moons. Saturn's rings, sharp and dazzling. And the lunar surface teems with craters and mountains in rugged relief.

While the Observer 90 EQ telescope excels at lunar and planetary observing, it can also provide great views of many more-distant objects. At 36x the Orion Nebula exhibits the four Trapezium stars as perfect blue pinpoints surrounded by greenish gas. Pop in the 10mm telescope eyepiece to boost the power to 90x and — wow! — The nebulosity spans nearly the entire eyepiece field of view! In the summer sky the Great Hercules Star Cluster (M13) starts to resolve into tiny stellar pinpoints.

The Observer 90 EQ telescope features a 1.25" rack-and-pinion focuser for dialing in the sharpest view. A 90-degree star diagonal inserted in the focuser provides a comfortable viewing angle. The 6x30 crosshair finder scope helps you locate your targets.

The Observer's sturdy equatorial mount can be quickly polar-aligned to allow easy "tracking" of celestial objects as they move slowly across the sky, using just one of the two slow-motion knobs. Use both to center objects in the telescope's field of view. The extendable aluminum telescope tripod provides solid support, and has an accessory tray to keep your extra eyepiece and Barlow within easy reach.

The telescope weighs under 17 lbs. total, including the easily removable counterweight, so it's easy to take outside for impromptu observing sessions.

Warranty

Limited Warranty against defects in materials or workmanship for one year from date of purchase. This warranty is for the benefit of the original retail purchaser only. For complete warranty details contact us at 800-447-1001.

Warning

Please note this product was not designed or intended by the manufacturer for use by a child 12 years of age or younger.

Product Support

Visit our product support section for instruction manuals and more

Specs

Best for viewing

Lunar & planetary
User level

User level

Beginner Level - Suited for a wide range of uses, these products are simple to operate and set up. Some initial assembly may be required depending on the type of product. Optical instruments with this rating will have very good optical and mechanical quality. Great for families, young people, and folks who don't want to mess with equipment and complexity. Beginning level telescopes will show you countless lunar craters, Saturn's rings and a myriad of star clusters and nebulae! Referring to the manual is recommended.

Intermediate Level - These products offer higher performance and more advanced features than Level 1: Beginner models. They typically take a bit longer to learn and need some set-up or adjustments. But anyone with the slightest technical bent will have no problem getting familiar with these models. Referring to the manual is recommended.

Advanced Level - These products provide the best performance but may require more skill to master and appreciate. Optical instruments with this rating have exceptionally fine optics and mechanics. Some are easy to use but might be on the large or heavy side. Some are intended for specialized uses. These products will appeal to the more technically inclined. Referring to the manual is highly recommended.

Beginner
Optical design

Optical design

Reflector telescopes use a pair of large and small mirrors to direct incoming light to the eyepiece. Refractor telescopes refract, or "bend" incoming light to a focus by means of an objective lens. Cassegrain telescopes, such as Maksutov-Cassegrains, "fold" incoming light using two mirrors and a front "corrector" lens.

Refractor
Optical diameter

Optical diameter

For telescopes, the optical diameter (also known as aperture) is the size of a telescope's main light-collecting lens or primary mirror, measured in millimeters or inches. Telescopes with larger optical diameters collect more light, which leads to an increase in brightness and image resolution compared to smaller instruments.

For binoculars, the optical diameter (also known as objective lens diameter) is the size of each of the front-facing objective lenses of a binocular measured in millimeters. Binoculars with larger objective lenses collect more light, which increases image resolution and brightness. Binoculars with larger objective lenses are recommended for low light situations, and binoculars with at least 50mm or larger objective lenses are recommended for pleasing astronomical observations at night.

90mm
Focal length

Focal length

The distance from the center of a curved mirror or lens at which parallel light rays converge to a single point. The focal length is an inherent specification of a mirror or lens and is one of the factors in determining resultant magnification for a telescope (along with the focal length of the eyepiece being used).

900mm
Focal ratio

Focal ratio

The focal ratio of an optical system is the ratio of a telescope's focal length to its aperture. Short focal ratios (f/5, f/4.5) produce wide fields of view and small image scales, while long focal lengths produce narrower fields of views and larger image scales.

f/10.0
Coatings

Coatings

Binocular lenses and prisms are often coated with anti-reflective material to minimize light loss as light travels through the multiple optical surfaces of a typical binocular. Coatings help maximize the amount of light transmitted through each glass surface of a binocular, so as much light as possible reaches the observer's eyes to provide a bright and sharp image.
Good lenses are at least "fully coated," with a single layer of magnesium fluoride coating applied to each air-to-glass lens surface. Multiple layers of coatings are even more effective; the term "multi-coated" means one or more air-to-glass lens surface has multiple coatings. "Fully multi-coated" optics are even better, meaning all lens surfaces have multiple layers of anti-reflective coatings applied for maximum light transmission and optimal image quality.

Fully coated
Optics type

Optics type

Newtonian reflectors will have either a spherical shaped mirror, which is less expensive to produce, or a higher quality parabola, which does not result in spherical aberration. Cassegrain telescopes routinely use spheres in addition to other lenses in the optical path to correct for residual spherical aberration. Refractors use a series of lenses to provide a clear image. Designs range from a standard air-spaced doublet (two lenses in a row) to exotic designs such as oil-spaced triplets and 4-element multi group lenses.

Air-spaced doublet
Glass material

Glass material

Refractors use glass lenses to focus the light, and the glass material plays an important role in the quality of the resulting image. Standard achromatic refractors routinely use Crown and Flint for the two elements, but more expensive apochromatic refractors can use ED (extra low dispersion) glass for one or more of the lenses. Reflector mirrors are made from glass with different levels of thermal expansion. Standard mirrors are made from material such as Soda-Lime Plate glass and BK-7 glass. Glass with Pyrex or other low thermal expansion material will not change shape as dramatically during the cool-down period, resulting in more stable images during this period.

Crown/Flint
Eyepieces

Plossl 25.0mm,10.0mm (1.25")
Magnification with included eyepieces

36x, 90x
Resolving power

Resolving power

The theoretical resolving power of a telescope can be calculated with the following formula: Resolving power (in arc seconds) = 4.56 divided by aperture of telescope (in inches). In metric units, this is: Resolving power (in arc seconds) = 116 divided by aperture of telescope (in millimeters). Note that the formula is independent of the telescope type or model, and is based only upon the aperture of the telescope. So the larger the telescope's aperture, the more it is capable of resolving. This is important to keep in mind when observing astronomical objects which require high resolution for best viewing, such as planets and double stars. However, it is usually atmospheric seeing conditions (not the telescope) which limits the actual resolving power on a given night; rarely is resolution less than one arc-second possible from even the best viewing locations on Earth.

1.29arc*sec
Lowest useful magnification

Lowest useful magnification

Lowest useful magnification is the power at which the exit pupil becomes 7mm in diameter. Powers below this can still be reached with the telescope to give wider fields of view, but the image no longer becomes brighter at a lower power. This is due to the fact that the exit pupil of the telescope (the beam of light exiting the eyepiece) is now larger than the average person's dark adapted pupil, and no more light can fit into the eye.

13x
Highest useful magnification

Highest useful magnification

The highest practical limit is different from the often used "highest theoretical magnification" specification. The "theoretical" limit generally is 50x the aperture of the scope in inches (2x the aperture in mm). So for example, an 80mm refractor is capable of 160x, and a 10" telescope is theoretically capable of 500x magnification. But after approximately 300x, theory breaks down and real world problems take over. The atmosphere above us is constantly in motion, and it will distort the image seen through the telescope. This effect may not be noticeable at lower powers, but at higher powers the atmosphere will dramatically blur the object, reducing the quality of the image. On a good night (a night where the air above is steady and the stars aren't twinkling), the practical upper limit of a large telescope is 300x, even thought the theoretical limit may be much higher. This doesn't mean the scope will never be able to reach those higher "theoretical" powers - there will be that rare night where the atmosphere is perfectly still and the scope can be pushed past it's practical limit, but those nights will be few and far between.

180x
Highest theoretical magnification

180x
Limiting stellar magnitude

Limiting stellar magnitude

The limiting stellar magnitude is a measure of the faintest star you can see through the telescope.

12.5
Optical quality

Optical quality

"Diffraction Limited" means that the limits of image detail are determined by the physical properties of light, and not by optical defects in the telescope.

Diffraction limited
Finder scope

6x30
Focuser

1.25" Rack-and-pinion
Diagonal degrees

1.25" 90° Mirror Star
Secondary mirror obstruction

40mm
Secondary mirror obstruction by diameter

30%
Secondary mirror obstruction by area

22%
Mirror coatings/over-coatings

Aluminum & Silicon Dioxide
Mount type

Equatorial
Dovetail bar system

Dovetail bar system

A universal attachment system for holding the optical tube onto the tripod. A dovetail bar is attached to the tube rings, then it slides onto the mount itself, making for quick assembly and disassembly.

Yes
Motor drive compatibility

Motor drive compatibility

A motor drive automatically moves the telescope in right ascension at the same rate as the east-west drift of the stars so stars can be continuously tracked in the eyepiece without manual adjustment. Motor drives are usually equipped with a hand control that allows the telescope's tracking speed to be slightly increased or decreased, which is particularly critical when taking long-exposure astro-images.

Clock drive sold separately
Setting circles

Yes
Polar-axis scope

Not available
Counterweights

One 4 lb.
Tube material

Aluminum
Tripod material

Aluminum
Counterweight bar length

8 in.
Diameter of counterweight shaft

13mm
Height range of mount

Height range of mount

The height range specification is a measure of the tripod itself - not the eyepiece height. Since telescopes come in all shapes and sizes, the eyepiece height will vary, even when using the same tripod. For an EQ tripod the mount is set up so the counterweight shaft is horizontal, and then the height is measured from the ground to the center of the mounting plate.

37.50 in. - 69.50 in.
Length of optical tube

34.0 in.
Weight, optical tube

4.7 lbs.
Weight, mount/tripod

11.4 lbs.
Weight, fully assembled

16.1 lbs.
Other features

Dual slow-motion cables, Dovetail saddle for easy attach/detach of OTA, Dew shield reduces off-axis glare and dew on lens
Warranty

Warranty

This warranty gives you specific legal rights. It is not intended to remove or restrict your other legal rights under applicable local consumer law; your state or national statutory consumer rights governing the sale of consumer goods remain fully applicable.

One year

In The Box

Optical tube assembly
EQ mount
Aluminum tripod
Accessory tray
6x30 finder scope with bracket
25mm Plossl eyepiece, 1.25"
10mm Plossl eyepiece, 1.25"
Star diagonal, 1.25"
Counterweight
Counterweight shaft
Slow-motion cables (x2)
Tube ring and dovetail mounting bar assembly

Shipping Info

Orders received by 1pm Eastern Standard Time for in-stock items ship the same business day. Order received after noon will ship the next business day. When an item is not in-stock we will ship it as soon as it becomes available. Typically in-stock items will ship first and backordered items will follow as soon as they are available. You have the option in check out to request that your order ship complete, if you'd prefer.

A per-item shipping charge (in addition to the standard shipping and handling charge) applies to this product due to its size and weight. This charge varies based on the shipping method.

Standard Delivery: $0.00
Standard Delivery to Canada: $25.00
3 Day Delivery: $25.00
2 Day Delivery: $25.00
Next Day Delivery: $25.00

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