With 120mm of clear aperture and 1000mm focal length, the Orion SkyView Pro 120mm Equatorial Refractor Telescope has the magnifying ability to split 2-arcsecond double stars and reveal subtle lunar and planetary features. With less chromatic aberration than short-focal-length achromatic refractors, the SkyView Pro 120mm provides pleasing star images with a minimum of color fringing.
It's the perfect refractor telescope for digital imaging. Pop on an Orion StarShoot Solar System imaging camera and you're all set to capture spectacularly detailed shots of Jupiter, Saturn, Mars, and lunar landscapes galore!
The telescope features a multi-coated 120mm (4.7") achromatic objective lens in an adjustable cell. The 2" aluminum rack-and-pinion focuser (with 1.25" adapter) allows use of optional 2" telescope eyepieces. The tube rides on the sturdy SkyView Pro equatorial telescope mount, which has a stainless steel tripod for superior rigidity. Standard accessories include an 8x40 finder scope, star diagonal, and two Sirius Plossl telescope eyepieces.
The Orion SkyView Pro 120mm Equatorial Refractor Telescope can be upgraded at any time to GoTo computerized object location. This standard configuration is compatible with optional TrueTrack electronic drives, allowing objects to be tracked after they are located.
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
Brighter deep sky
Best for imaging
Finder scope lens diameter
Sirius Plossl 25.0mm,10.0mm (1.25")
Magnification with included eyepieces
Highest theoretical magnification
1.25" 90° Mirror Star
Lunar, planetary & long exposure
Clock drive sold separately
Intelliscope system or Go-To system
Sealed ball bearings
One 7.5 lb., one 4 lb.
Tripod leg diameter
Counterweight bar length
Diameter of counterweight shaft
Length of optical tube
Weight, optical tube
Weight, fully assembled
Additional included accessories
Adjustable lens cell, 2" focuser
In The Box
Orion optical tube assembly
25mm Orion Sirius Plössl telescope eyepiece (1.25")
10mm Orion Sirius Plössl telescope eyepiece (1.25")
90º mirror star diagonal (1.25")
2" - 1.25" telescope eyepiece adapter
Equatorial telescope mount
8x40 finder scope
Orion finder scope bracket with O-ring
Tube ring mounting plate
7.3 lb counterweight
3.8 lb counterweight
Tripod accessory tray
Slow-motion control knobs
R.A. axis rear cover
Latitude adjustment L-bolt
Starry Night special edition software
Orders received by 1pm Eastern Time for in-stock items ship the same business day. Orders received after 1pm 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: $106.00
2 Day Delivery: $106.00
Next Day Delivery: $130.00
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 SkyView Pro 120mm EQ Refractor, which has a focal length of 1000mm, used in combination with the supplied 25mm eyepiece, yields a power of: 1000 ÷ 25 = 40x.
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. 240x for the SkyView Pro 120mm). 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 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.
How do you 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 an 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 align a polar finder?
This procedure is complicated and it is not required for casual observing, but here it goes . . . Remove the cover cap from the front opening in the R.A. axis of the telescope mount. Look through the polar finder at a distant object. Focus the polar finder so that the images and reticle are sharp by rotating the eyepiece end of the finder. Notice that the reticle pattern consists of a crosshair with a circle around the middle. On the circumference of this circle is a tiny circle; this is where Polaris will be placed for accurate polar alignment once the finder is properly aligned. Alignment of the polar finder is best done during the day, before going out into the field at night. Aligning the polar axis finder scope so that it will accurately point at the true north pole is a two-step procedure. First, the polar finder must be rotated in its housing so that the small circle in which Polaris will be placed in is in the proper initial position. Next, the polar axis finder must be adjusted so that it points directly along the mount’s R.A. axis. 1. Loosen the R.A. setting circle lock thumb screw, located just above the R.A. setting circle. Rotate the R.A. setting circle until the line above the “0” on the setting circle lines up with the pointed indicator that is cast into the mount. Retighten the thumbscrew. 2. Rotate the date circle until the “0” line on the meridian off-set scale lines up with the time meridian indicator mark. The meridian offset scale is printed on the inner circumference of the date circle, and is labeled “E20” to “W20”. The time meridian indicator mark is an engraved line on the exterior of the polar finder�s housing. It is on the “ring” of the housing that is closest to the date circle. 3. The R.A. setting circle is labeled in hours, from “0” to “23” (military time). For Northern Hemisphere observers, refer to the top numbers on the setting circle. Each small line represents 10 minutes of R.A. The date circle is labeled from “1” to “12”, with each number representing a month of the year (“1” is January, “2” is February, etc.). Each small line represents a two-day increment. 4. Loosen the R.A. lock lever and rotate the mount about the R.A. axis until the March 1 indicating mark (the long line between the “2” and the “3”) on the date circle lines up with the 4 PM mark (the long line above the “16”) on the R.A. setting circle. You may find it convenient to remove both the counterweights and the telescope optical tube to do this. 5. Now, loosen the three thumbscrews on the polar finder housing and rotate the polar finder so the small circle where Polaris will be centered is located straight down from the intersection of the crosshairs. Retighten the thumbscrews. The polar axis finder scope is now properly set in its initial position. Next, you must align it so that it is exactly parallel to the mount’s R.A. axis. 6. Look through the polar finder at a distant object (during the day) and center it in the crosshairs. You may need to adjust the latitude adjustment T-bolts and the tripod position to do this. 7. Rotate the mount 180-deg about the R.A. axis. Again, it may be convenient to remove the counterweights and optical tube first. 8. Look through the polar finder again. Is the object being viewed still centered on the crosshairs? If it is, then no further adjustment is necessary. If not, then look through the polar finder while rotating the mount about the R.A. axis. You will notice that the object you have previously centered moves in a circular path. Use the three thumbscrews on the housing to redirect the crosshairs of the polar finder to the apparent center of this circular path. Repeat this procedure until the position that the crosshairs point to does not rotate off-center when the mount is rotated in R.A. Once this is accomplished, retighten the thumbscrews. The polar axis finder scope is now ready to be used. When not in use, replace the plastic protective cover to prevent the polar finder from getting bumped, which could knock it out of alignment.
How do I point the telescope on an 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. Directly south: 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 Setting Circles and how do you 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-archmin 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. (Insert a Link)
how do you 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�) 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 Photographs?
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" 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.
What is piggybacking photography and how do you do it?
The Moon and planets are interesting targets for the budding astrophotographer, but what next? Literally thousands of deep-sky objects can be captured on film with a type of astrophotography called “piggybacking”. The basic idea is that the camera with its own camera lens attached rides on top of the main telescope. The telescope and camera both move with the rotation of the Earth when the mount is polar aligned and the motor drive is engaged. This allows for a long exposure through the camera without having the object or background stars blurred. In addition to the motor drive (dual-axis), and illuminated reticle eyepiece is also needed. The T-ring and camera adapter are not needed, since the camera is exposing through its own lens. Any camera lens with a focal length between 35mm and 400mm is appropriate. On the top of one of the tube rings is a piggyback camera adapter. This is the black knob with the threaded shaft protruding through it. The tube ring with the piggyback adapter should be closest to the open end of the telescope tube. Remove the tube rings from the equatorial mount and swap their position if necessary. Now, connect the camera to the piggyback adapter. There should be a 1/4"-20 mounting hole in the bottom of the camera’s body. Thread the protruding shaft of the piggyback adapter into the 1/4"-20 mounting hole in the camera a few turns. Position the camera so it is parallel with the telescope tube and turn the knurled black knob of the piggyback adapter counter-clockwise until the camera is locked into position. Aim the telescope at a deep-sky object. It should be a fairly large deep-sky object, as the camera lens will likely have a wide field of view. Check to make sure that the object is also centered in the camera’s viewfinder. Turn the motor drive on. Now, look into the telescope’s eyepiece and center the brightest star within the field of view. Remove the eyepiece and insert the illuminated reticle eyepiece into the focuser draw-tube. Turn the eyepiece’s illuminator on (dimly!). Re-center the bright star (guide star) on the crosshairs of the reticle eyepiece. Check again to make sure that the object to be photographed is still centered within the camera’s field of view. If it is not, re-center it by repositioning the camera on the piggy-back adapter, or by moving the main telescope. If you move the main telescope, then you will need to re-center another guide star on the illuminated eyepiece’s crosshairs. Once the object is centered in the camera and a guide star is centered in the reticle eyepiece, you’re ready to shoot. While exposing through the camera lens, you will need to monitor the accuracy of the mount’s tracking by looking through the illuminated reticle eyepiece in the main telescope. If the guide star drifts from its initial position, then use the hand controller of the motor drive to “move” the guide star back to the center of the crosshairs. Any drifting along the Dec. axis is a result of improper polar alignment, so if the guide star drifts greatly in Dec., the mount may need to be polar aligned more accurately. When the exposure is complete, unlock the shutter release cable and close the camera’s shutter. A few hints from Orion astrophographers: Film speed can be anything from 100-1600, slower film yields less “grainy” results, but requires longer exposure times. Older manual cameras work better for piggyback photography than electronic cameras. Most lenses are sharpest closed down one stop from full open. Astrophotography can be enjoyable and rewarding, as well as frustrating and time-consuming. Start slowly and consult outside resources, such as books and magazines, for more details about astrophotography. Remember. . . have fun!
How do you take solar Photographs?
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" with an off-axis mask.