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° 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 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 120mm EQ Refractor Telescope, which has a focal length of 600mm, used in combination with the supplied 25mm eyepiece, yields a power of: 600 ÷ 25 = 24x.
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 Orion Astroview 120mm Refractor). Atmospheric conditions will limit the usefullness of magnification and cause views to become blurred. The highest useful magnification of a telescope of the Orion Astroview 120mm is 300x. 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. See our Learning Center articles: About General Astronomy
How big a telescope do I need?
For viewing craters on the Moon, the rings of Saturn, and Jupiter with its four bright moons, a 60mm or 70mm refractor or a 3-inch reflector telescope does a good job. An 80mm to 90mm refractor or 4.5-inch or 6-inch reflector will show more planetary and lunar detail as well as glowing nebulas and sparkling star clusters. Under dark, non-light-polluted skies, a big scope—8-inch diameter or more—will serve up magnificent images of fainter clusters, galaxies, and nebulas. The larger the telescope, the more detail you will see. But don’t bite off more than you can chew, size-wise. Before you buy, consider carefully a telescope’s size and weight. Make sure you can comfortably lift and transport it, and that you have room indoors to store it. For more detailed information on this topic see our Learning Center article: Choosing a Telescope for Astronomy - The long Version
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 advice . . .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 will a star look like through a telescope?
Stars will appear like twinkling points of light in the telescope. Even the largest telescopes cannot magnify stars to appear as anything more than points of light. You can, however, enjoy the different colors of the stars and locate many pretty double and multiple stars. The famous “Double-Double” in the constellation Lyra and the gorgeous two-color double star Albireo in Cygnus are favorites. Defocusing the image of a star slightly can help bring out its color. For more detailed information on this topic see our Learning Center article: Stars and Deep Sky Objects
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.
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° 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° 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° 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° 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 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.
What is the advantage of a dual axis electronic drive over a single axis drive?
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 dial axis system comes in especially handy foot observing at high powers and is a must for long-exposure astrophotography.
What are the Setting Circles and what do they do?
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.
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.
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.
Is there an image quality difference between a short-tube and long-tube?
Short refractors have more visible chromatic aberration than long refractors. You’re likely to see purple or orange halos around bright planets and the lunar limb. With short reflectors, “coma” comes into play: stars appear like “commas” or “seagulls” near the edge of the eyepiece field. For most people, a little color fringing or coma is no big deal. These aberrations are less noticeable at low magnifications, which is one reason not to push the power higher than about 100x in most short-tube telescopes. High-end short-tubes made with exotic glasses or with corrector lenses can handle higher power. For more detailed information on this topic see our Learning Center article: Short Tube vs Long Tube- What’s the Difference