Our compact, performance-packed Orion StarBlast 4.5 EQ Reflector telescope is a favorite of both beginners and expert astronomers alike. It combines the much-heralded parabolic optics of our Orion StarBlast 4.5" wide-field (f/4.0) reflector telescope with our sturdy EQ-1 equatorial tracking mount and adjustable-height tripod.
The 4.5" aperture reflector telescope's short focal length serves up a generous chunk of sky in the eyepiece, making it easy for beginners to find celestial objects to study. This tripod-mounted version of the StarBlast 4.5 reflector offers an even more pronounced wide-field viewing experience compared to its tabletop counterpart, as we've upgraded the telescope eyepieces to include two from the Orion Expanse series - a 15mm and 6mm - which have a large 66° apparent field of view. Observations of everything from the Moon to Messier objects appear exceptionally sharp and rich in contrast through this petite reflector telescope.
Start each stargazing session with the 15mm Expanse eyepiece for medium-power views.
When inserted in the StarBlast 4.5 EQ reflector telescope, the included 15mm Orion Expanse eyepiece provides a 30x view with a wide, 66° apparent field of view. The 15mm Expanse ocular is a great eyepiece to use when you first begin your telescopic observations each night, since it provides a large window of night sky for you to view. You'll get wonderful views of deep space objects like star clusters and cloudy nebulas.
Increase magnification for more powerful views with the 6mm Expanse eyepiece.
After you've scanned the skies with the 15mm Expanse in the StarBlast 4.5 EQ, take a much closer look at interesting objects by swapping out the 15mm eyepiece with 6mm Expanse to boost magnification all the way up to 75x. The more powerful view provided by the 6mm focal length eyepiece makes it easier to discern details such as craters and mountains on the Moon, as well as details of bright planets like the moons of Jupiter and the rings of Saturn.
The included Orion EZ Finder II red-dot sight makes aiming the telescope nice and easy.
The Orion EZ Finder II reflex sight makes it easy to aim the StarBlast 4.5 Equatorial Reflector Telescope anywhere in the night sky. Following a simple alignment procedure, the EZ Finder II projects a small red-dot onto a viewing window so all you have to do is move the telescope until the red-dot is aimed at the area of sky you wish to view through the telescope. With the EZ Finder II reflex sight, starhopping around the sky is a breeze for anyone in the family!
Learn about the night sky with the included Starry Night Special Edition software.
Explore starry skies anytime - even when it's cloudy! The Orion StarBlast 4.5 EQ telescope includes a FREE Special Edition of Starry Night astronomy software. With realistic sky simulations and a many useful features including telescope control, the user-friendly Starry Night Special Edition software will help you plan your observations and understand what you see. Requires PC running Windows XP, Vista, 7 or 8. Requires Macintosh running OS X 10.4 or higher.
With the included Orion EQ-1 equatorial telescope mount, you will be able to keep your target object centered in the telescope eyepiece with only an occasional tweak of one slow-motion cable. The EQ-1, like all equatorial telescope mounts, orients the attached StarBlast 4.5" reflector telescope on two axes of motion (right ascension and declination), allowing you to easily track celestial objects as they appear to move across the night sky. Thanks to this design, it's easy for anyone in the family to manually track a celestial object using slow-motion control cables. You can even add an optional electronic motor drive (sold separately) to the EQ-1 equatorial mount so it can track objects automatically once you've centered the object in the telescope eyepiece. The adjustable-height aluminum tripod allows you to set the StarBlast 4.5 Equatorial Reflector up for comfortable views, while remaining lightweight so the entire assembled telescope is easy to transport to and from your favorite stargazing location.
If you're looking for an exceptional beginner telescope on a stable mount with slow-motion tracking control, or if you're seeking a second telescope that's more portable than your big "light bucket", then get an Orion StarBlast 4.5 Equatorial Reflector Telescope. Trust us, you'll have a blast!
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
Lunar & planetary
Expanse 15.0mm,6.0mm (1.25")
Magnification with included eyepieces
Highest theoretical magnification
EZ Finder II
Secondary mirror obstruction
Secondary mirror obstruction by diameter
Secondary mirror obstruction by area
Aluminum & Silicon Dioxide
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
Additional included accessories
In The Box
Orion 4.5" f/4.0 reflector telescope optical tube assembly
15mm Orion Expanse telescope eyepiece (1.25")
6mm Orion Expanse telescope eyepiece (1.25")
EQ-1 equatorial telescope mount
EZ Finder II reflex sight aiming device
Tripod accessory tray
Slow-motion control cables
Latitude adjustment T-bolt
Starry Night Special Edition astronomy software download card
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: $32.00
2 Day Delivery: $32.00
Next Day Delivery: $39.00
How can I check the collimation of my reflector?
Collimation is the process of adjusting the telescope’s mirrors so they are perfectly aligned with one another. Your telescope’s optics were aligned at the factory, and should not need much adjustment unless the telescope is handled roughly. Mirror alignment is important to ensure the peak performance of your telescope, so it should be checked regularly. Collimation is relatively easy to do and can be done in daylight. To check collimation, remove the eyepiece and look down the focuser drawtube. You should see the secondary mirror centered in the drawtube, as well as the reflection of the primary mirror centered in the secondary mirror, and the reflection of the secondary mirror (and your eye) centered in the reflection of the primary mirror. If anything is off-center, proceed with the collimation procedure. The faster the f/ratio of your telescope, the more critical the collimation accuracy.
How do I align the primary mirror with the collimation cap and center-marked mirror?
The telescope’s primary mirror will need adjustment if the secondary mirror is centered under the focuser and the reflection of the primary mirror is centered in the secondary mirror, but the small reflection of the secondary mirror (with the “dot” of the collimation cap) is off-center. The tilt of the primary mirror is adjusted with the larger collimation screws on the back end of the telescope’s optical tube. The other smaller screws lock the mirror’s position in place; these thumbscrews must be loosened before any collimation adjustments can be made to the primary mirror. To start, loosen the smaller thumbscrews that lock the primary mirror in place a few turns each. Use a screwdriver in the slots, if necessary. Now, try tightening or loosening one of the larger collimation screws with your fingers Look into the focuser and see if the secondary mirror reflection has moved closer to the center of the primary. You can tell this easily with the collimation cap and mirror center mark by simply watching to see if the “dot” of the collimation cap is moving closer or further away from the “ring” on the center of the primary mirror mark. When you have the dot centered as much as is possible in the ring, your primary mirror is collimated. Re-tighten the locking thumbscrews. Alternative: If you loosen one or more of the bolts too much, it won’t move the mirror. Some people prefer to pre-load the collimation screws by tightening them all down and adjust by loosening each one in turn. This way you don’t run-out of threads and have a loose collimation screw. The disadvantage to this approach is that you have completely un-collimated the scope and are starting from the beginning.
How do I align the EZ Finder II and EZ finder Deluxe?
When the EZ Finder is properly aligned with the telescope, an object that is centered on the EZ Finder red dot should also appear in the center of the field of view of the telescope’s eyepiece. Alignment of the EZ Finder is easiest during daylight, before observing at night. Aim the telescope at a distant object such as a telephone pole or roof chimney and center it in the telescope’s eyepiece. The object should be at least 1/4 mile away. Now, with the EZ Finder turned on, look though the EZ Finder. The object should appear in the field of view. Without moving the main telescope, use the EZ Finder’s azimuth (left/right) and altitude (up/down) adjustment to position the red dot on the object in the eyepiece. When the red dot is centered on the distant object, check to make sure that the object is still centered in the telescope’s field of view. If not, re-center it and adjust the EZ Finder’s alignment again. When the object is centered in the eyepiece and on the EZ Finder’s red dot, the EZ Finder is properly aligned with the telescope. Once aligned, EZ Finder will usually hold its alignment even after being removed and remounted. Otherwise, only minimal realignment will be needed.
How do I replace the EZ finder II battery?
Should the battery ever die, replacement 3-volt lithium batteries are available from Orion and many retail outlets. The finder uses a CR-2032 battery. Remove the old battery from the EZ finder II by inserting a small flat-head screwdriver into the slot on the battery casing and gently prying open the case. Then carefully pull back on the retaining clip and remove the old battery. Do not over-bend the retaining clip. Then slide the new battery under the battery lead with the positive (+) end facing down and replace the battery casing.
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 StarBlast 4.5 Equatorial Reflector Telescope, which has a focal length of 450mm, used in combination with the supplied 15mm eyepiece, yields a power of: 450 ÷ 15 = 30x.
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. 225x for the Orion StarBlast 4.5). 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. See our Learning Center articles: About General Astronomy
What is the best telescope for a beginner?
The “best scope” for anyone is highly subjective and varies based on the person who will be using the telescope. Their level of interest in the hobby, their aptitude for “the technical”, the level of investment that you want to make, and the ability to carry differing weights. For more detailed information on this topic see our Learning Center article: How to Choose a Telescope
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 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.
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. For more details, see our learning center article Observing 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
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?
Orion carries 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 clean the reflecting mirror of my telescope?
You should not have to clean the telescope’s mirrors very often; normally once every other year or even less often. Covering the telescope with the dust cover when it is not in use will prevent dust from accumulating on the mirrors. Improper cleaning can scratch mirror coatings, so the fewer times you have to clean the mirrors, the better. Small specks of dust or flecks of paint have virtually no effect on the visual performance of the telescope. The large primary mirror and the elliptical secondary mirror of your telescope are front-surface aluminized and over-coated with hard silicon dioxide, which prevents the aluminum from oxidizing. These coatings normally last through many years of use before requiring re-coating. To clean the secondary mirror, first remove it from the telescope. Do this by holding the secondary mirror holder stationary while turning the center Phillips-head screw. Be careful, there is a spring between the secondary mirror holder and the phillips head screw. Be sure that it will not fall into the optical tube and hit the primary mirror. Handle the mirror by its holder; do not touch the mirror surface. Then follow the same procedure described below for cleaning the primary mirror. To clean the primary mirror, carefully remove the mirror cell from the telescope and remove the mirror from the mirror cell. If you have an Orion telescope, instructions to remove the primary mirror are included in your instruction manual. Do not touch the surface of the mirror with your fingers. Lift the mirror carefully by the edges. Set the mirror on top, face up, of a clean soft towel. Fill a clean sink, free of abrasive cleanser, with room-temperature water, a few drops of mild liquid dishwashing soap, and, if possible, a capful of rubbing alcohol. Submerge the mirror (aluminized face up) in the water and let it soak for a few minutes (or hours if it’s a very dirty mirror). Wipe the mirror under water with clean cotton balls, using extremely light pressure and stroking in straight line across the mirror. Use one ball for each wipe across the mirror. Then rinse the mirror under a stream of lukewarm water. Before drying, tip the mirror to a 45 degree angle and pour a bottle of distilled water over the mirror. This will prevent any tap water dissolved solids from remaining on the mirror. Any particles on the surface can be swabbed gently with a series of cotton balls, each used just one time. Dry the mirror in a stream of air (a “blower bulb” works great), or remove any stray drops of water with the corner of a paper towel. Water will run off a clean surface. Cover the mirror surface with tissue, and leave the mirror in a warm area until it is completely dry before replacing in the mirror cell and telescope.
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 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 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°), 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.
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.