As any telescope aficionado will tell you, the virtue of refractors lies in their pristine image quality. The only challenge to owning a refractor has always been the price: refractors cost more per inch of aperture than any other telescope design. That's still true, but steady advances in precision lens manufacturing technology are bringing those prices down.
Way down, in the case of our remarkable Orion AstroView 90mm Equatorial Refractor Telescope. This impressive 90mm refractor telescope is priced to please, without compromising the quality of the optics, equatorial mount or standard accessories, we might add. This is a soundly constructed, great performing telescope that any new backyard astronomer or experienced stargazer will appreciate from the first night out.
The Orion AstroView 90mm EQ Refractor is a planetary power-performer with its 90mm aperture and 910mm focal length. Views of the planets and Moon through the f/10 AstroView 90 telescope are nothing short of spectacular. When aimed at our nearest neighbor in space, the Moon, the AstroView 90 yields tack-sharp views of the rocky lunar surface with craters and mountainous regions visible in crisp, high-contrast detail. You'll find yourself transfixed by the rugged relief of the Moon's surface as shadows along the terminator enchant your eyes. On a reasonably clear evening, Jupiter's cloud banding becomes starkly visible in the AstroView 90mm EQ, as do all four of its major Galilean moons. Depending on the time of year, the Orion AstroView 90mm EQ Refractor can also provide the whole family with jaw-dropping views of Saturn and its stunning rings, not to mention glimpses of big Saturnian moon Titan.
With 90mm of aperture, the AstroView 90mm Equatorial Refractor Telescope can also provide great views of many deep-sky phenomena. With the 25mm Plossl eyepiece installed in the telescope to provide 36x power magnification, our namesake deep-sky object, the Orion Nebula, exhibits the four Trapezium stars as perfect blue pinpoints surrounded by a pretty patch of greenish gas. If you pop in the included 10mm eyepiece to bump up the power to 91x magnification - Wow! - the nebula will appear sprout cloudy wings, which span nearly the entire eyepiece field of view!
The AstroView 90mm refractor is supported by the substantial Orion EQ-2 equatorial mount, which allows for easy manual tracking of celestial objects as they appear to migrate across the night sky. An occasional tweak of the equatorial mount's R.A. (Right Ascension) slow-motion cable will keep any object centered in the telescope eyepiece. You can also use an optional electronic motor drive for more automated, hands-free tracking of any centered object (drives sold separately). An adjustable tripod lets you set the telescope to a comfortable height for a long night of solo stargazing, or you can change the height throughout the evening for a night of family fun with the stars. There's even a handy accessory tray that fits onto the tripod for convenient storage of gear while you're out in the field.
The Orion AstroView 90mm Equatorial Refractor Telescope will provide you and your family with many evenings of heavenly browsing at an unbelievably low price. The telescope comes fully equipped with a 6x30 achromatic finder scope, two fully coated 1.25" Sirius Plössl telescope eyepieces (25mm and 10mm), a 90° mirror star diagonal, dust cap, and 1/4"-20 adapter on one of the tube rings for piggyback camera attachment. The assembled telescope weighs just 23.7 lbs. total, so it's easy to take outside for impromptu observing sessions.
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 800-676-1343.
Please note this product was not designed or intended by the manufacturer for use by a child 12 years of age or younger.
Visit our product support section for instruction manuals and more
Best for viewing
Lunar & planetary
Best for imaging
Lunar & planetary
Finder scope magnification
Finder scope lens diameter
Sirius Plossl 25.0mm, 10.0mm
Magnification with included eyepieces
Highest theoretical magnification
1.25" 90° Mirror Star
Clock drive sold separately
One 4.8 lb.
Counterweight bar length
Diameter of counterweight shaft
Length of optical tube
Weight, optical tube
Weight, fully assembled
In the Box
Orion 90mm f/10.1 refractor telescope Optical Tube Assembly (OTA)
25mm Orion Sirius Plössl telescope eyepiece (1.25")
10mm Orion Sirius Plössl telescope eyepiece (1.25")
90º Mirror star diagonal (1.25")
Orion Equatorial mount
Orion 6x30 finder scope
Finder scope bracket with O-ring
Tripod accessory tray
Slow-motion control cables
Accessory tray bracket
Flat-head screwdriver key
Starry Night Special Edition astronomy software
Orders received by noon Pacific Time for in-stock items ship the same business day. Orders 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
3 Day Delivery: 54.00
2 Day Delivery: 54.00
Next Day Delivery: $63.00
How do I align a finder scope?
Before you use the finder scope, it must be precisely aligned with the telescope so they both point to exactly the same spot. Alignment is easiest to do in daylight, rather than at night under the stars. First, insert a low power telescope eyepiece (a 25mm eyepiece will work great) into the telescope’s focuser. Then point the telescope at a discrete object such as the top of a telephone pole or a street sign that is at least a quarter-mile away. Position the telescope so the target object appears in the very center of the field of view when you look into the eyepiece. Now look through the finder scope. Is the object centered on the finder scope’s crosshairs? If not, hopefully it will be visible somewhere in the field of view, so only small turns of the finder scope bracket’s alignment thumb screws will be needed. Otherwise you’ll have to make larger turns to the alignment thumb screws to redirect the aim of the finder scope. Use the alignment thumb screws to center the object on the crosshairs of the finder scope. Then look again into the telescope’s eyepiece and see if it is still centered there too. If it isn’t, repeat the entire process, making sure not to move the telescope while adjusting the alignment of the finder scope. Finder scopes can come out of alignment during transport or when removed from the telescope, so check its alignment before each observing session.
How do I focus the finder scope?
If, when looking through the finder scope, you notice that the image is fuzzy, you will need to focus the finder scope for your eyes. Different finder scopes focus differently; most Orion finder scopes include a lock ring near the objective and focus as follows:
1. Loosen the lock ring that is located behind the finder’s objective lens cell
2. Screw the objective lens cell in or out until the image appears sharp.
3. Tighten the lock ring behind the lens cell. If there is no lock ring the finder scope is focused by rotating the eyepiece.
Once the finder scope is now focused it should not need focusing again for your eyes..
Can the finder scope crosshairs be adjusted?
Yes, but before taking this on, regardless of the orientation, the intersection of the crosshairs marks the center and that’s what important. However, should you feel the need to change the orientation of the finder scope’s crosshairs; you can do so by carefully rotating the finder scope in its bracket. Loosen the adjustment screws or pull on the tensioner (depending on the model) and rotate the finder scope tube in the bracket until the crosshairs are oriented the way you want. You should not need to rotate the finder scope tube more than 1/4 of a turn. For right-angle finder scopes, unthread the eyepiece to re-orient the crosshairs; gently turn the eyepiece until the crosshairs are oriented as you wish. You should not need to rotate the eyepiece more than 1/4 of a turn to do this. This may leave you with a loose eyepiece. If so, you can add an o-ring or shim to tighten it at the new orientation.
How do I calculate the magnification (power) of a telescope?
To calculate the magnification, or power, of a telescope with an eyepiece, simply divide the focal length of the telescope by the focal length of the eyepiece. Magnification = telescope focal length ÷ eyepiece focal length. For example, the Orion Astroview 90mm EQ Refractor, which has a focal length of 910mm, used in combination with the supplied 25mm eyepiece, yields a power of: 910 ÷ 25 = 36x.
It is desirable to have a range of telescope eyepieces of different focal lengths to allow viewing over a range of magnifications. It is not uncommon for an observer to own five or more eyepieces. Orion offers many different eyepieces of varying focal lengths.
Every telescope has a theoretical limit of power of about 50x per inch of aperture (i.e. 180x for the Astroview 90mm). Atmospheric conditions will limit the usefullness of magnification and cause views to become blurred. Claims of higher power by some telescope manufacturers are a misleading advertising gimmick and should be dismissed. Keep in mind that at higher powers, an image will always be dimmer and less sharp (this is a fundamental law of optics). With every doubling of magnification you lose half the image brightness and three-fourths of the image sharpness. The steadiness of the air (the “seeing”) can also limit how much magnification an image can tolerate. Always start viewing with your lowest-power (longest focal length) eyepiece in the telescope. It’s best to begin observing with the lowest-power eyepiece, because it will typically provide the widest true field of view, which will make finding and centering objects much easier After you have located and centered an object, you can try switching to a higher-power eyepiece to ferret out more detail, if atmospheric conditions permit. If the image you see is not crisp and steady, reduce the magnification by switching to a longer focal length eyepiece. As a general rule, a small but well-resolved image will show more detail and provide a more enjoyable view than a dim and fuzzy, over-magnified image.
What are practical focal lengths to have for eyepieces for my telescope?
To determine what telescope eyepieces you need to get powers in a particular range with your telescope, see our Learning Center article: How to choose Telescope Eyepieces
Why do Orion telescopes have less power than the telescope at department stores?
Advertising claims for high magnification of 400X, 600X, etc., are very misleading. The practical limit is 50X per inch of aperture, or 120X for a typical 60mm telescope. Higher powers are useless, and serve only to fool the unwary into thinking that magnification is somehow related to quality of performance. It is not.
How do I get started with astronomical viewing?
When choosing a location for nighttime stargazing, make it as far away from city lights as possible. Light-polluted skies greatly reduce what can be seen with the telescope. Also, give your eyes at least 20 minutes to dark-adapt to the night sky. You’ll be surprised at how many more stars you will see! Use a red flashlight, to see what you’re doing at the telescope, or to read star charts. Red light will not spoil your dark-adapted night vision as readily as white light will. To find celestial objects with your telescope, you first need to become reasonably familiar with the night sky. Unless you know how to recognize the constellation Orion, for instance, you won’t have much luck locating the Orion Nebula. A simple planisphere, or star wheel, can be a valuable tool for learning the constellations and seeing which ones are visible in the sky on a given night. A good star chart or atlas, like the Orion DeepMap 600, can come in handy for helping locate interesting objects among the dizzying multitude of stars overhead. Except for the Moon and the brighter planets, it is pretty time-consuming and frustrating to hunt for objects randomly, without knowing where to look. It is best to have specific targets in mind before you begin looking through the eyepiece. Practice makes perfect. After a few nights, this will begin to “click” and star-hopping will become easier.
Why would I want a manual scope when I can get a Go-To scope?
For the novice stargazer, buying a computer-controlled telescope with a small aperture puts a lot of money into the mechanical and database components of the telescope to locate objects that you can’t see with the optics of the telescope. Someone who is inexperienced with astronomy and night sky will spend their time pouring over instruction manuals and text scrolling across a screen instead of exploring the night sky, studying the stars and their patterns and learning how to locate to binary stars and nebula. Our advise . . . go for bigger aperture.
What causes dim or distorted images?
Too much magnification
Keep in mind that at higher powers, an image will always be dimmer and less sharp (this is a fundamental law of optics). The steadiness of the air, the seeing, can also limit how much magnification an image can tolerate. Always start viewing with your lowest-power (longest focal length) eyepiece in the telescope. It’s best to begin observing with the lowest-power eyepiece, because it will typically provide the widest true field of view, which will make finding and centering objects much easier After you have located and centered an object, you can try switching to a higher-power eyepiece to ferret out more detail, if atmospheric conditions permit. If the image you see is not crisp and steady, reduce the magnification by switching to a longer focal length telescope eyepiece. As a general rule, a small but well-resolved image will show more detail and provide a more enjoyable view than a dim and fuzzy, over-magnified image. As a rule of thumb, it is not recommended to exceed 2x per mm of aperture.
Atmospheric conditions aren’t optimal.
Atmospheric conditions vary significantly from night to night, even hour to hour . “Seeing” refers to the steadiness of the Earth’s atmosphere at a given time. In conditions of poor seeing, atmospheric turbulence causes objects viewed through the telescope to “boil.” If, when you look up at the sky with just your eyes, the stars are twinkling noticeably, the seeing is bad and you will be limited to viewing with low powers (bad seeing affects images at high powers more severely). Seeing is best overhead, worst at the horizon. Also, seeing generally gets better after midnight, when much of the heat absorbed by the Earth during the day has radiated off into space. It’s best, although perhaps less convenient, to escape the light-polluted city sky in favor of darker country skies.
Viewing through a glass window open or closed.
Avoid observing from indoors through an open (or closed) window, because the temperature difference between the indoor and outdoor air, reflections and imperfections in the glass, will cause image blurring and distortion.
Telescope not at thermal equilibrium.
All optical instruments need time to reach “thermal equilibrium.” The bigger the instrument and the larger the temperature change, the more time is needed. Allow at least a half-hour for your telescope to cool to the temperature outdoors. In very cold climates (below freezing), it is essential to store the telescope as cold as possible. If it has to adjust to more than a 40 degrees temperature change, allow at least one hour. Time to adjust varies depending on the scope type and aperture.
Make sure you are not looking over buildings, pavement, or any other source of heat, which will radiate away at night, causing “heat wave” disturbances that will distort the image you see through the telescope.
Does the atmosphere play a role in how good the quality of the image will be?
Atmospheric conditions play a huge part in quality of viewing. In conditions of good “seeing”, star twinkling is minimal and objects appear steady in the eyepiece. Seeing is best over-head, worst at the horizon. Also, seeing generally gets better after midnight, when much of the heat absorbed by the Earth during the day has radiated off into space. Typically, seeing conditions will be better at sites that have an altitude over about 3000 feet. Altitude helps because it decreases the amount of distortion causing atmosphere you are looking through. A good way to judge if the seeing is good or not is to look at bright stars about 40 degrees above the horizon. If the stars appear to “twinkle”, the atmosphere is significantly distorting the incoming light, and views at high magnifications will not appear sharp. If the stars appear steady and do not twinkle, seeing conditions are probably good and higher magnifications will be possible. Also, seeing conditions are typically poor during the day. This is because the heat from the Sun warms the air and causes turbulence. Good “transparency” is especially important for observing faint objects. It simply means the air is free of moisture, smoke, and dust. These tend to scatter light, which reduces an object’s brightness. One good way to tell if conditions are good is by how many stars you can see with your naked eye. If you cannot see stars of magnitude 3.5 or dimmer then conditions are poor. Magnitude is a measure of how bright a star is, the brighter a star is, the lower its magnitude will be. A good star to remember for this is Megrez (mag. 3.4), which is the star in the “Big Dipper” connecting the handle to the “dipper”. If you cannot see Megrez, then you have fog, haze, clouds, smog, light pollution or other conditions that are hindering your viewing. Another hint: Good seeing can vary minute to minute. Watch the planets for a while to pick-up those moments of good seeing.
How long will it take my eyes to dark adapt?
Do not expect to go from a lighted house into the darkness of the outdoors at night and immediately see faint nebulas, galaxies, and star clusters—or even very many stars, for that matter. Your eyes take about 30 minutes to reach perhaps 80 percent of their full dark-adapted sensitivity. Many observers notice improvements after several hours of total darkness. As your eyes become dark-adapted, more stars will glimmer into view and you will be able to see fainter details in objects you view in your telescope. So give yourself at least a little while to get used to the dark before you begin observing. To see what you are doing in the darkness, use a red light flashlight rather than a white light. Red light does not spoil your eyes’ dark adaptation like white light does. A flashlight with a red LED light is ideal, or you can cover the front of a regular flashlight with red cellophane or paper. Beware, too, that nearby porch and streetlights and automobile headlights will spoil your night vision. Your eyes can take at least 1/2 hour to re-adjust.
How do I see the best detail on the surface of the Moon?
The Moon, with its rocky, cratered surface, is one of the easiest and most interesting subjects to observe with your telescope. The myriad craters, rilles, and jagged mountain formations offer endless fascination. The best time to observe the Moon is during a partial phase, that is, when the Moon is not full. During partial phases, shadows cast by crater walls and mountain peaks along the border between the dark and light portions of the lunar disk highlight the surface relief. A full Moon is too bright and devoid of surface shadows to yield a pleasing view. Try using an Orion Moon filter to dim the Moon when it is too bright; it simply threads onto the bottom of the eyepiece, you’ll see much more detail.
How do I best view Deep-Sky Objects?
Most deep-sky objects are very faint, so it is important that you find an observing site well away from light pollution. Take plenty of time to let your eyes adjust to the darkness. Don’t expect these objects to appear like the photographs you see in books and magazines; most will look like dim gray “ghosts.” (Our eyes are not sensitive enough to see color in deep-sky objects except in few of the brightest ones.) But as you become more experienced and your observing skills improve, you will be able to coax out more and more intricate details. And definitely use your low-power telescope eyepieces to get a wide field-of-view for the largest of the deep-sky objects.
What will the planets look like through the telescope?
The planets don’t stay put like stars do (they don’t have fixed R.A. and Dec. coordinates), so you will need to refer to the Orion Star Chart on our website. Venus, Mars, Jupiter, and Saturn are among the brightest objects in the sky after the Sun and the Moon. All four of these planets are not normally visible in the sky at one time, but chances are one or two of them will be.
JUPITER: The largest planetJupiter, is a great subject to observe. You can see the disk of the giant planet and watch the ever-changing positions of its four largest moons, Io, Callisto, Europa, and Ganymede. If atmospheric conditions are good, you may be able to resolve thin cloud bands on the planet’s disk.
SATURN: The ringed planet is a breathtaking sight when it is well positioned. The tilt angle of the rings varies over a period of many years; sometimes they are seen edge-on, while at other times they are broadside and look like giant “ears” on each side of Saturn’s disk. A steady atmosphere (good seeing) is necessary for a good view. You may probably see a tiny, bright “star” close by; that’s Saturn’s brightest moon, Titan.
VENUS: At its brightest, Venus is the most luminous object in the sky, excluding the Sun and the Moon. It is so bright that sometimes it is visible to the naked eye during full daylight! Ironically, Venus appears as a thin crescent, not a full disk, when at its peak brightness. Because it is so close to the Sun, it never wanders too far from the morning or evening horizon. No surface markings can be seen on Venus, which is always shrouded in dense clouds. Sometimes using a color filter will lessen the glare of Venus and help you see the crescent.
MARS: If atmospheric conditions are good, you may be able to see some subtle surface detail on the Red Planet, possibly even the polar ice cap. Mars makes a close approach to Earth every two years; during those approaches its disk is larger and thus more favorable for viewing. For more detailed information on this topic see our Learning Center article: What Will You See Through a Telescope
How do I find Deep-sky Objects: Starhopping
Starhopping, as it is called by astronomers, is perhaps the simplest way to hunt down objects to view in the night sky. It entails first pointing the telescope at a star close to the object you wish to observe, and then progressing to other stars closer and closer to the object until it is in the field of view of the eyepiece. It is a very intuitive technique that has been employed for hundreds of years by professional and amateur astronomers alike. Keep in mind, as with any new task, that starhopping may seem challenging at first, but will become easier over time and with practice. To starhop, only a minimal amount of additional equipment is necessary. A star chart or atlas that shows stars to at least magnitude 5 is required. Select one that shows the positions of many deep-sky objects, so you will have a lot of options to choose from. If you do not know the positions of the constellations in the night sky, you will need to get a planisphere to identify them. Start by choosing bright objects to view. The brightness of an object is measured by its visual magnitude; the brighter an object, the lower its magnitude. Choose an object with a visual magnitude of 9 or lower. Many beginners start with the Messier objects, which represent some of the best and brightest deep-sky objects, first catalogued about 200 years ago by the French astronomer Charles Messier. Determine in which constellation the object lies. Now, find the constellation in the sky. If you do not recognize the constellation on sight, consult a planisphere. The planisphere gives an all-sky view and shows which constellations are visible on a given night at a given time. Now look at your star chart and find the brightest star in the constellation that is near the object that you are trying to find. Using the finder scope, point the telescope at this star and center it on the crosshairs Next, look again at the star chart and find another suitably bright star near the bright star currently centered in the finder. Keep in mind that the field of view of the finder scope is between 5-deg - 7-deg, so you should choose a star that is no more than 7-deg from the first star, if possible. Move the telescope slightly, until the telescope is centered on the new star. Continue using stars as guideposts in this way until you are the approximate position of the object you are trying to find. Look in the telescope’s eyepiece, and the object should be somewhere within the field of view. If it’s not, sweep the telescope carefully around the immediate vicinity until the object is found. If you have trouble finding the object, start the starhop again from the brightest star near the object you wish to view. This time, be sure the stars indicated on the star chart are in fact the stars you are centering in the finder scope and telescope eyepiece. Remember the telescope and the finder scope will give you inverted images (unless you are using a correct image finder scope), keep this in mind when you are starhopping from star to star. Observing Hint: Always use your lowest powered eyepiece in your telescope when starhopping . This will give you the widest possible field of view.
Can I wear my glasses when using a telescope?
If you wear eyeglasses, you may be able to keep them on while you observe, if your telescope eyepieces have enough “eye relief” to allow you to see the whole field of view. You can find out by looking through the eyepiece first with your glasses on and then with them off, and see if the glasses restrict the view to only a portion of the full field. If they do, you can easily observe with your glasses off by just refocusing the telescope the needed amount. If your eyes are astigmatic, images will probably appear the best with glasses on. This is because a telescope’s focuser can accommodate for nearsightedness or farsightedness, but not astigmatism. If you have to wear your glasses while observing and cannot see the entire field of view, you may want to purchase additional eyepieces that have longer eye relief.
What eyepiece should I use for terrestrial viewing?
For land viewing, it’s best to stick with low power eyepieces that yield a magnification under 100x. At higher powers, images rapidly lose sharpness and clarity due to “heat waves” caused by Sun-heated air. Remember to aim well clear of the Sun, unless the front of the telescope is fitted with a professionally made solar filter and the finder scope is removed or covered with foil or some other completely opaque material. Many Orion telescopes are capable of focusing on objects that are quite close, so you can view fine details of objects that are nearby. Try focusing on a flower or insect at close distance to enter a normally unseen microscopic world. Check the specifications on the product web page or instruction manual for your Orion scope. Observing hint: If the object is too close to focus. You may be able to use an extension tube that allows the eyepiece to move further back as you focus closer. Try lifting the eyepiece out of the holder as you look. If it focuses in about an inch or two, you can purchase an eyepiece extension tube. For more detailed information on this topic see our Learning Center article: Choosing Eyepieces
Is there an eyepiece available that will rotate the image so that it can be used for scenic viewing?
We carry correct-image prism diagonals which provide right-side up non-reversed images in refractor and cassegrain telescopes. It is not possible to correct the image orientation in a reflector telescope.
How do I clean any of the optical lenses?
Any quality optical lens cleaning tissue and optical lens cleaning fluid specifically designed for multi-coated optics can be used to clean the exposed lenses of your eyepieces or finder scope. Never use regular glass cleaner or cleaning fluid designed for eyeglasses. Before cleaning with fluid and tissue, blow any loose particles off the lens with a blower bulb or compressed air. Then apply some cleaning fluid to a tissue, never directly on the optics. Wipe the lens gently in a circular motion, then remove any excess fluid with a fresh lens tissue. Oily finger-prints and smudges may be removed using this method. Use caution; rubbing too hard may scratch the lens. On larger lenses, clean only a small area at a time, using a fresh lens tissue on each area. Never reuse tissues.
Does my telescope require time to cool down?
As a general rule, telescopes should be allowed to cool down (or warm up) before they are used. If you bring optics from a warm air to cold air (or vice versa) without giving it time to reach thermal equilibrium, your telescope will give you distorted views. Allow your telescope 30 minutes to an hour to reach the temperature of the outdoors before using. When brining your telescope from cool temperatures to warm temperatures, leave any protective caps off until the telescope has warmed-up to prevent condensation. Storing your telescope in the garage or shed where the temperature is closer to the outside temperature will reduce cool down times.
How do I polar align my equatorial mount?
For Northern Hemisphere observers, approximate polar alignment is achieved by pointing the mount’s R.A. axis at the North Star, or Polaris. It lies within 1-deg of the north celestial pole (NCP), which is an extension of the Earth’s rotational axis out into space. Stars in the Northern Hemisphere appear to revolve around Polaris. To find Polaris in the sky, look north and locate the pattern of the Big Dipper. The two stars at the end of the “bowl” of the Big Dipper point right to Polaris. Observers in the Southern Hemisphere aren’t so fortunate to have a bright star so near the south celestial pole (SCP). The star Sigma Octantis lies about 1-deg from the SCP, but it is barely visible with the naked eye (magnitude 5.5). For general visual observation, an approximate polar alignment is sufficient: 1. Level the equatorial mount by adjusting the length of the three tripod legs. 2. Loosen one of the latitude adjusting T-bolts and tighten the other to tilt the mount until the pointer on the latitude scale is set at the latitude of your observing site. This may vary depending on the mount, some have one bolt and a tightening screw instead. If you don’t know your latitude, consult a geographical atlas to find it. For example, if your latitude is 35-deg North, set the pointer to +35. The latitude setting should not have to be adjusted again unless you move to a different viewing location some distance away. 3. Loosen the Dec. lock lever and rotate the telescope optical tube until it is parallel with the R.A. axis. The pointer on the Dec. setting circle should read 90-deg. Retighten the Dec. lock lever. 4. Move the tripod so the telescope tube (and R.A. axis) points roughly at Polaris. If you cannot see Polaris directly from your observing site, consult a compass and rotate the tripod so the telescope points north. Using a compass is a less desirable option, a compass points about 16-deg away from true north and requires you to compensate foe accurate polar alignment. The equatorial mount is now approximately polar-aligned for casual observing. More precise polar alignment is required for astrophotography and for use of the manual setting circles. From this point on in your observing session, you should not make any further adjustments to the latitude of the mount, nor should you move the tripod. Doing so will undo the polar alignment. The telescope should be moved only about its R.A. and Dec. axes.
How do I point the telescope using my Equatorial Mount?
Beginners occasionally experience some confusion about how to point the telescope overhead or in other directions.
At the zenith:
You want to view an object that is directly overhead, at the zenith. DO NOT make any adjustment to the latitude adjustment T-bolts. That will spoil the mount’s polar alignment. Remember, once the mount is polar aligned, the telescope should be moved only on the R.A. and Dec. axes. To point the scope overhead, first loosen the R.A. lock lever and rotate the telescope on the R.A. axis until the counterweight shaft is horizontal (parallel to the ground). Then loosen the Dec. lock lever and rotate the telescope until it is pointing straight overhead. The counterweight shaft is still horizontal. Then retighten both lock levers.
Directly north at an object that is nearer to the horizon than Polaris:
You can’t do it with the counterweight down. You have to rotate the scope in R.A. so that the counterweight shaft is positioned horizontally. Then rotate the scope in Dec. so it points to where you want it near the horizon.
The counterweight shaft should again be horizontal. Then you simply rotate the scope on the Dec. axis until it points in the south direction.
East or west:
To point the telescope to the east or west, or in other directions, you rotate the telescope on its R.A. and Dec. axes. Depending on the altitude of the object you want to observe, the counterweight shaft will be oriented somewhere between vertical and horizontal.
Another hint: On some smaller scopes the RA slow-motion shaft can get in the way of some orientations. If this occurs, simply remove the slow-motion knobs and re-attach to the other side of the RA axis.
How do I track Celestial Objects with an Equatorial Mount?
When you observe a celestial object through the telescope, you’ll see it drift slowly across the field of view. To keep it in the field, if your equatorial mount is polar-aligned, just turn the R.A. slow-motion control. The Dec. slow-motion control is not needed for tracking, but may be required to center the object. Objects will appear to move faster at higher magnifications, because the field of view is narrower. A DC motor drive system can be mounted on all Orion equatorial mounts to provide hands-free tracking. Motor drive systems are typically offered as an optional accessory. Objects will then remain stationary in the field of view without any manual adjustment of the R.A. slow-motion control. A dual-axis motor drive is necessary for astrophotography.
How do I drive my Telescope?
One of the benefits of a telescope on an equatorial mount is that it can accept an electronic motor drive to “track” the motion of the stars.
Without a drive an object will drift out of the field of view (due to the earth’s rotation). And, while every equatorial mount come with “slow motion” control controls that allow you to reposition the scope by hand to keep objects in view, an electronic drive does this automatically by exactly countering the rate of Earth’s rotation. It lets you observe that planet or nebula continuously without having to manually tweak the telescope’s potion again and again.
There are two basic types of electronic drive systems; single axis and dual axis. A single axis drive is a single motor that couples to the R.A. axis of the equatorial mount and drives the scope from East to West to provides basic star tracking. For general astronomical observing, a single axis drive is usually sufficient.
A dual axis drive motorizes both axes of motion of the equatorial mount. It provides the basic tracking function as well as fine control of the telescope position in any direction. A dual axis system comes in especially handy for observing as high powers and is a must for long-term astrophotography.
So, why not let your telescope do the driving!
What are the Setting Circles and how do I use them?
The setting circles on an equatorial mount enable you to locate celestial objects by their “celestial coordinates”. Every object resides in a specific location on the “celestial sphere”. That location is denoted by two numbers: its right ascension (R.A.) and declination (Dec.). In the same way, every location on Earth can be described by its longitude and latitude. R.A. is similar to longitude on Earth, and Dec. is similar to latitude. The R.A. and Dec. values for celestial objects can be found in any star atlas or star catalog. The R.A. setting circle is scaled in hours, from 1 through 24, with small marks in between representing 10 minute increments (there are 60 minutes in 1 hour of R.A.). The upper set of numbers apply to viewing in the Northern Hemisphere, while the numbers below them apply to viewing in the Southern Hemisphere. The Dec. setting circle is scaled in degrees, with each mark representing 2-deg increments. Values of Dec. coordinates range from +90-deg to -90-deg. The 0-deg mark indicates the celestial equator. When the telescope is pointed north of the celestial equator, values of the Dec. setting circle are positive, while when the telescope is pointed south of the celestial equator, values of the Dec. setting circle are negative. So, the coordinates for the Orion Nebula listed in a star atlas will look like this: R.A. 5h 35.4m Dec. -5-deg 27’ That’s 5 hours and 35.4 minutes in right ascension, and -5 degrees and 27 arc-minutes in declination (there are 60 arc-minutes in 1 degree of declination). Before you can use the setting circles to locate objects, the mount must be well polar aligned, and the R.A. setting circle must be calibrated. The Dec. setting circle has been calibrated at the factory, and should read 90-deg whenever the telescope optical tube is parallel with the R.A. axis. Click here for information on calibrating the RA Axis.
How do I find Objects With the Setting Circles?
Look up in a star atlas the coordinates of an object you wish to view. 1. Loosen the Dec. lock lever and rotate the telescope until the Dec. value from the star atlas matches the reading on the Dec. setting circle. Remember that values of the Dec. setting circle are positive when the telescope is pointing north of the celestial equator (Dec. = 0-deg), and negative when the telescope is pointing south of the celestial equator. Retighten the lock lever. 2. Loosen the R.A. lock lever and rotate the telescope until the R.A. value from the star atlas matches the reading on the R.A. setting circle. Remember to use the upper set of numbers on the R.A. setting circle. Retighten the lock lever. The lower set is for the Southern Hemisphere. Most setting circles are not accurate enough to put an object dead-center in the telescope’s eyepiece, but they should place the object somewhere within the field of view of the finder scope, assuming the equatorial mount is accurately polar aligned. Use the slow-motion controls to center the object in the finder scope, and it should appear in the telescope’s field of view. The R.A. setting circle must be re-calibrated every time you wish to locate a new object. Do so by calibrating the setting circle for the centered object before moving on to the next one.
I set the Setting Circles but there’s nothing there. . .
Most setting circles are not accurate enough to put an object dead-center in the telescope’s eyepiece, but they should place the object somewhere within the field of view of the finder scope, assuming the equatorial mount is level and accurately polar-aligned. Use the slow-motion controls to center the object in the finder scope, and it should appear in the telescope’s field of view. The R.A. setting circle must be re-calibrated every time you wish to locate a new object. Do so by calibrating the setting circle for the centered object before moving on to the next one.
How do I calibrate the right ascension setting circle?
1. Identify a bright star in the sky near the celestial equator (Dec. = 0-deg) and look up its coordinates in a star atlas. 2. Loosen the R.A. and Dec. lock levers on the equatorial mount, so the telescope optical tube can move freely. 3. Point the telescope at the bright star whose coordinates you know. Lock the R.A. and Dec. lock levers. Center the star in the telescope’s field of view with the slow-motion control cables. 4. Loosen the R.A. setting circle lock thumbscrew (if there is a thubmscrew, some RA circles don’t have a set screw they use friction), this will allow the setting circle to rotate freely. 5. Rotate the setting circle until the arrow under the thumbscrew indicates the R.A. coordinate listed in the star atlas for the object. 6. Do not retighten the thumbscrew when using the R.A. setting circles for finding objects; the thumbscrew is only needed for polar alignment using the polar axis finder scope.
The AstroTrack or AccuTrack motor drive is turned on, but the telescope does not move or is tracking intermittently.
Here are some things to check: 1. Is the telescope properly balanced? The motor provides only limited torque, so if the telescope is not balanced on both the right ascension and declination axes, the imbalance may put stress on the motor and inhibit the smooth movement of the telescope. 2. Is the coupling thumbscrew on the motor’s drive coupling tight against the R.A. shaft on the equatorial telescope mount? If it is loose, the R.A. shaft may not be turning at the same rate as the motor coupling, or at all. Make sure the thumbscrew is tight against the flat spot on the shaft. If it’s not on the flat spot, even when very tight, it can slip. You can use the position of the set screw on the opposite side (the slow-motion knob) to determine where the flat spot is on the motor side. 3. The torque needed to rotate the R.A. worm gear may be set too high. Careful attention must be paid to the amount of torque needed to rotate the R.A. worm gear. If the amount of torque seems great (the R.A. slow-motion control is hard to turn), the motor may be hindered and will provide unreliable tracking (or the motor could suffer damage). Diagrams and troubleshooting the torque of the R.A. worm gear are included in the Orion motor drive instruction manuals.
When I use my motor drive, the moon drifts from the field of view.
The moon moves at a slightly slower rate from East to West than sidereal rate, so the motor speed needs to be reduced. If it North or South, the polar alignment should be checked.
How do I take Planetary Photos?
Once basic Moon photography has been mastered, it’s time to get images of the planets. This type of astrophotography also works to get highly magnified shots of the Moon. In addition to the T-ring, you will need a Universal 1.25 inch Camera Adapter. A motor drive system (single or dual axis) is also required. This is because a longer exposure is necessary, which would cause the image to blur if no motor drive was used for tracking. The equatorial mount must be accurately polar aligned, too. As before, connect the T-ring to your camera. Before connecting the Universal camera adapter to the T-Ring, an eyepiece must be inserted and locked into the body of the Universal camera adapter. Start by using a medium-low power eyepiece (about 25mm); you can increase the magnification later with a high-power eyepiece. Then connect the entire camera adapter, with eyepiece inside, to the T-Ring. Insert the whole system into the telescope’s focuser drawtube and secure firmly with the thumbscrews. Aim the telescope at the planet (or Moon) you wish to shoot. The image will be highly magnified, so you may need to use the finder scope to center it within the camera’s viewfinder. Turn the motor drive on. Adjust the telescope’s focuser so that the image appears sharp in the camera’s viewfinder. The camera’s shutter is now ready to be opened. A remote shutter release or shutter timer must be used or the image will be blurred beyond recognition. Try exposure times between 1 and 10 seconds, depending upon the brightness of the planet to be photographed and the ISO of the film being used. We’ve also seen good digital snapshots of images taken through the telescope’s eyepiece with the SteadyPix adapter.
How do I take solar Photos?
By attaching a camera body to a telescope, in effect using the scope as a telephoto lens, you can take striking photographs of the Sun. Only attempt this if the telescope is equipped with the proper solar filter. Solar filters are coated to a neutral density of 5, which reduces the light about 100,000 times. Depending on the aperture and focal length of your telescope and “seeing” conditions, you will need to experiment to find the best exposure time for your equipment. We recommend starting with an ISO rating of around 400. At prime focus, start with an exposure of about 1/250 second. Experiment with different shutter speeds. When using higher magnifications, longer exposures will generally be necessary. If you are a beginner in astrophotography and need further information, there are books available that cover this subject completely. Do not be discouraged if your first attempts at solar photography are less than desired. The Sun is very difficult to photograph because of poorer “seeing” conditions caused by unavoidable heat currents associated with daytime viewing. The highest possible resolution for any land-based telescope, regardless of location, is about 1 arc second. Ideal seeing for any location will be available less than 5% of the time. It may be some consolation to consider that your results could equal those at professional observatories, as larger apertures and location have little, if any, advantage. During bad seeing conditions, it may help to “stop down” apertures over 5-inches with an off-axis mask.
I recently purchased a solar filter for my telescope and can’t see anything with it. Any suggestions?
One of the problems with a solar filter on a telescope is that it’s a bit tricky to aim it at the sun. You can’t look through the finder to point the scope or you’ll cause injury to your eye. So, cap off or remove the finder. Also, because with the very dark filter on the front if the sun is slightly outside the field of view of the eyepiece you’ll see pitch blackness in the field. With the solar filter properly mounted, try looking at the shadow of the optical tube on the ground, move the tube until the shadow is at a minimum. You’ll be pointed at the sun, or at least close enough to find it with a little sweeping and a low-power eyepiece to bring it into view. It can be difficult, even with the shadow method. An other trick to try after you’ve got it close with the shadow if your still not having any luck getting the sun in the field...take the eyepiece out of the focuser. Then look into the focuser...you won’t see an image but when the sun gets close you’ll see a flicker of brightness coming through the mirrors. Then pop the eyepiece back in and you should have it.