Saxon - Binoculars and Telescopes

Frequently Asked Questions (Back to the Support page)
About Telescopes	About Binoculars
What can I see with my telescope? Will I see objects as they appear in photographs? How much power does my telescope have? What is the advantage of a large aperture telescope? What type of eyepiece should I buy? Which mount should I buy for my telescope? Should I get a motor drive with my equatorial mount? Should I use colour filters? What is GO-TO System use for? How do I safely transport my telescope? How do I store my telescope? How do I find objects in the sky? How do I find objects using the setting circles? How do I polar align my telescope? What is polarscope? How do I use it? I want to take photographs through my telescope. What do I do? I am observing Jupiter but I only see a shimmering disk. What am I doing wrong? What is an eyepiece? What is a Barlow Lens? Will a telescope work without an eyepiece? How much magnification can I use with my telescope? What is Apparent Field? What is Eye Relief? The image with my low power eyepiece is clear, but my high power is fuzzy. What's wrong with it? Which eyepiece design is best? What is Exit Pupil? Is high magnification better? Which eyepiece should I choose? Why are some eyepiece more expensive than others? Why is the image better at the center of the field? What is the black spot I see in a low powered eyepiece in my reflector during daylight? What is the "Kidney Bean Effect"? Which works better? An eyepiece or a Barlow+eyepiece giving the same magnification? How important it is to get a parfocal series of eyepiece? Do anit-reflection coatings improve light transmission? When I'm observing a bright object like a planet, I see an opposing ghost image. What causes that? How many eyepieces should I have? I’m trying to collimate my reflector but all I see at the back of my telescope is 3 Phillip’s-head screws. Where are the 2 sets of screws?	How can I choose the right binoculars for myself? How far can I see with your binoculars? What is the "Optical Quality" of binoculars? Isn't Higher Power better in a binocular? What is "Objective Lenses" of Binoculars? What is "Prisms" of Binoculars? What is "Eyepieces" of Binoculars? What is "Specifications" of Binoculars? What is "Magnification" of Binoculars? What is "Field of View" of Binoculars? What is "Eye Relief" of Binoculars? What is "Lens Coating" of Binoculars? What is "multi-coating"? What is the difference between multi-coated and fully multi-coated optics? What is the "Armor" of Binoculars? What is "Exit Pupil Diameter"? Will I need a tripod to my binocular? What is the "Mini Binoculars" can do? Why are the "Compact Binoculars" popular? What do the "Standard Porro Prism Binoculars" can do? How do "Zoom Binoculars" work? What are the advantages of "Standard Waterproof and Porro Prism Binoculars"? What can "Large Aperture Binoculars" do? What's the difference between BAK4 and BK-7 prisms? How to Clean Binoculars? Can I use your large-aperture binoculars for terrestrial observation & spotting? Can I use my binoculars to observe the moon and planets? Could large-aperture binoculars offer the same image quality as my premium telescope? What’s the difference between “roof prism” and “porro prism” binoculars? What is the difference between “center focus” and “IF”, or individual focus binoculars, and is one better than the other? What is binoculars “shockproof” for? What is “light gathering power”? Why does my binocular show distortion near the edge of the field of view, and does this mean that the binocular is defective? What is “phase-coatings”? What is the "Near Focus" for? What are the Focus Types? Why does only one eyepiece can be adjusted for my binoculars? What are the keys for image quality?
About Telescopes What can I see with my telescope? Astronomically, you can see the Moon, the Sun if correctly filtered, all of the planets except perhaps Pluto, some surface details on Mars, Jupiter and Saturn, multiple stars, globular and open clusters, bright nebulae, galaxies and nearby galaxy clusters. Terrestrially, there are wildlife, sports, etc., but remember that daytime viewing is often over areas which may radiate heat so that very distant subjects may shimmer. Back to top Will I see objects as they appear in photographs? Yes and no. Bright objects like the Moon, some planets and some star clusters will show colours and features just like photographs, but faint objects are more difficult. The eye is not sensitive enough to detect colour at low light levels so even bright nebulae appear as shades of gray in small telescopes. Colour films and digital images can be exposed long enough to collect light across the visible spectrum so photographs show colours than you don't see visually. Back to top How much power does my telescope have? A telescope has three types of power and they are measured against the performance of a normal human eye. They are magnifying power, light gathering power and resolving power. All three are important but the most important is resolving power. The longer the focal length of a telescope, the more a particular eyepiece will magnify the image. However, there is a practical magnification limit of 2x per mm of telescope aperture. Using an eyepiece which gives a magnification beyond that limit is normally of little use. The amount of light that a telescope can gather depends on size of the aperture and the more light that can be gathered, the better the resolution. What you will see through your telescope will then depend on these three powers. For example, compared to the human eye, and using the 2x per mm rule, a 150mm aperture telescope will have a maximum practical magnifying power of 300x, a light gathering power of 600x and a resolving power of 0.8 arc-seconds. Back to top What is the advantage of a large aperture telescope? The larger the aperture, the higher the practical magnification limit. Since more light is collected and brought to focus by a larger aperture telescope, fainter objects can be seen with it than with smaller apertures. Under good seeing conditions when air is not turbulent, a larger aperture objective gives higher resolution, letting you see finer details. Back to top What type of eyepiece should I buy? For standard eyepieces with a 50 degree apparent field of view, Plössl eyepieces are a good choice if your telescope's focal ratio is f7 or less. For longer focal ratio instruments, simpler eyepieces such as Kellners will be sufficient. Choose eyepiece focal lengths that won't give you a duplicate magnification when a Barlow lens is used. For example, don't get 10mm and 20mm eyepieces with a 2x Barlow. Back to top Which mount should I buy for my telescope? If your instrument is for land use only, select the alt-azimuth mounting, but if its for astronomical or dual use, the equatorial mounting is the best choice. Make sure that the mounting you select is strong enough to carry the telescope you've chosen. Heavier or longer telescopes need stronger mounts to be stable at high magnifications. When in doubt, over-mount the instrument; choose the mount one size up if you want extra stability. Back to top Should I get a motor drive with my equatorial mount? A motor drive is necessary for many types of astrophotography, but it is more than just a convenience for visual observation as well. At 200x magnification, the Earth's rotation will move an object out of your field of view in about twenty seconds. A Right Ascension motor drive will keep an object in the centre of the field where the image is the best without producing the objectionable vibrations experienced with manual tracking. Adding a Declination motor drive and a hand controller allows you to guide for astrophotography. Back to top Should I use colour filters? Colour filters, which usually thread into the eyepiece barrel, are almost a necessity for viewing planetary detail. By using an appropriate colour, you can highlight a specific planetary feature. This often allows you see two to three times as much detail as in an unfiltered view. Back to top What is GO-TO System use for? SAXON offers simple solutions for users who would like to attach their smaller telescope to a convenient computerized system but do not wish to deal with the weight of the HEQ5 mount. It allows you to point the telescope at a specific object or even tour the skies at the touch of a button. The EQ3 & EQ5 GO-TO mounts are the perfect instrument for novice visual observers to enjoy astronomy with minimal setup time and in-depth knowledge of the night sky. Positioning Accuracy up to 1 arc minute. Accuracy enhanced by software collimation error (mount mechanical error) compensation. Stepper motors with 1.8° step angle and 32 micro steps driven. Slewing speed up to 3.4°/sec (800X). Guiding speed selectable from 0.25X, 0.50X, 0.75X, or 1X. Object database containing complete Messier, NGC, and IC catalogues. Periodic Error Correction. PC compatibility. Upgradeable hand control via internet download. Back to top How do I safely transport my telescope? The telescope can be transported in 2 main parts--telescope tube and mount. Loosen the thumbscrews on the tube rings and remove the telescope tube from the mount. We suggest removing the accessories (finderscope and bracket, and the eyepiece) from the optical tube. Cover the telescope tube and the eyepiece with their caps. It is also convenient to remove the fine-adjustment control cables and counterweight rod/counterweights. The accessory tray should be removed in order to transport with the 3 tripod legs closed. The telescope can be transported in a vehicle without a problem. Padded insulation can prevent scratches on the tube but it is not necessary. The mirrors may go out of collimation after a bumpy ride but collimation may be required after transportation anyway, with or without padding. Back to top How do I store my telescope? It is unnecessary to separate the optical tube and the mount when storing the telescope. It can be stored in one unit in a clean, dry, and dust-free environment. If it has to be stored outdoors, cover it with a heavy-duty plastic cover to prevent it from getting wet. Make sure that the dust cap for the front of the telescope and the cover for the rear opening are on. Accessories should be stored separately in a box, with all their caps on. Some people do store the reflecting telescope in two parts, leaving the telescope tube up side down on the ground to prevent dust from settling down on the primary mirror. However, it is not proven that it really helps. Back to top How do I find objects in the sky? The sky is mapped out in a spherical coordinate system similar to the system of Latitude and Longitude on the surface of the Earth. On the imaginary celestial sphere, the coordinates are Declination, which is equivalent to Latitude and measured in degrees, and Right Ascension, which is equivalent to Longitude, but measured in hours. The celestial equator is a projection of the Earth's equator onto the celestial sphere. Because the positions of stars and other distant celestial objects, as plotted on this celestial sphere, change very slowly with time, their listed coordinates and star charts are only updated every fifty years. On the other hand, planets change position so rapidly that their coordinates must be obtained from current astronomy periodicals. The setting circles on your equatorial mount can be aligned with the celestial sphere to aid in finding astronomical objects. Back to top How do I find objects using the setting circles? Periodicals like "SkyNews", "Sky&Telescope" and "Astronomy" will tell you where the moon and planets are, and the location of all other objects can be found in Star Charts. The quickest way to find objects is to learn the Constellations and use the finderscope, but if the object is too faint you may want to use setting circles. Download the PDF file to find out how to use the setting circles on your saxon mounts. (You will need Adobe Acrobat Reader to open the file.) Back to top How do I polar align my telescope? For visual use, only a rudimentary alignment of the polar axis of your equatorial mount is required. First, the finderscope should already have been aligned to the telescope by centring a distant fixed object in the telescope's field and then adjusting the finderscope with its adjusting screws until the object is at the centre of the crosshairs. The angle of the polar axis should also be set equal to your Latitude. Now, with the mount approximately level, align the telescope parallel to the polar axis (ie set the Declination axis to 90 degrees). In the northern hemisphere, adjust the polar axis until the star Polaris (the "North star") appears in the centre of the field of your finderscope. This alignment is good enough for visual observation. If you are trying astrophotography, a more accurate alignment is required, and you will need a polarscope if your mount is equipped for it. For longer exposure times, the mount is usually adjusted using a very accurate star-movement measurement technique called "drift alignment." Back to top What is a polarscope? How do I use it? A polarscope is a specialised finderscope which is used to align an equatorial mount with the celestial pole. It is usually mounted in a tube which runs along the RA axis. For northern use, it will have a mark for Polaris, the pole star, which is slightly offset from the North Celestial Pole. It must be rotated so that the offset mark of Polaris is correctly aligned relative to the direction of epsilon-Cassiopeia on a line from it (through Polaris) to Alkaid, the end star on the Big Dipper's handle. For the southern hemisphere, four stars of the constellation Octans will be marked in the polarscope. These need to be placed over the real stars in the sky, by rotating the polarscope and adjusting the pointing of the polar axis. Back to top I want to take photographs through my telescope. What do I need? Most telescopes can be adapted to act as lenses for single lens reflex (SLR) cameras. For the basic technique of "prime focus" photography, all you generally need are a camera body, a T-ring specifically made for your camera body (allows it to connect to a T-thread) and in some cases a combination T-adapter designed for your telescope (supplies the T-thread). This configuration, is fine for terrestrial use, or for the Moon or the correctly filtered Sun, but for fainter astronomical objects you will need to do time exposures using an equatorial mount with a Right Ascension motor to correct for the Earth's rotation. For exposures longer than a few seconds, you should use dual axis motor drives and a hand controller to guide the telescope. Back to top I am observing Jupiter but I only see a shimmering disk. What am I doing wrong? Astronomers must be patient; you must optimise your observing site and times, as well as your equipment. When you observe the Moon and the planets, and they appear as though water is running over them, you probably have bad "seeing" because you are observing through turbulent air. Always observe objects as high in the sky as possible. Don't observe immediately after sunset and avoid viewing across heat-radiating ground objects such as buildings and parking lots. Let your telescope come to temperature with the surrounding air; sometimes the shimmering is due to "tube currents" within the telescope tube. Try to enhance planetary detail by using colour filters. Optimise all that you can then be patient because good seeing comes and goes. Back to top What is an eyepiece? An eyepiece is a magnifier, much like a high power magnifying glass. When placed at the real image made by the lens or mirror of a telescope, the eyepiece projects a virtual image into your eye, enabling you to see the target. Back to top What is a Barlow Lens? A barlow lens has a negative focal length which increases the effective focal length (E.F.L) of the objective lens or mirror of the telescope. It is always placed between the objective and the eyepiece and results in increased magnification and decreased field of view. Back to top Will a telescope work without an eyepiece? Not for visual purposes, as the eye cannot process the real image made by the objective. The telescope may be used without an eyepiece for cameras and other instruments. Back to top How much magnification can I use with my telescope? Every telescope is different, but a rough rule of thumb is 30-50X per inch diameter of the objective. A good refractor may, however, use 100X/inch on bright objects, so this is not a hard rule. You can always increase the magnification above these limits, but it is pointless if you're not seeing more. This rule breaks down for larger instruments, as the distortion of the atmosphere limits practical magnification to 300X. Back to top What is Apparent Field? Apparent Field (A.F.) is the angle viewed by the eye when looking into the eyepiece. An eye by itself has an A.F. of about 100 degrees, so any well corrected design up to this value would be a benefit. Back to top What is Eye Relief? Eye relief, also known as exit pupil distance, is maximum distance between the eye and the eye lens of the eyepiece to see the eyepiece's field stop. (The field stop is the baffle at the image plane that produces the field edge.) Adequate eye relief is a very important factor for comfortable viewing. Eye relief generally decreases as power increases. Low eye relief (less than 10mm) requires you to get very close to the eyepieces, while higher eye relief (greater than 15mm) allows more distance. Eyeglass wearers need a higher amount of eye relief to allow room for their eyeglasses, however- many eyeglass wearers are surprised to find that they don't need their glasses when viewing through telescopes. Back to top The image with my low power eyepiece is clear, but my high power is fuzzy. What's wrong with it? There's likely nothing wrong with the eyepiece: you have probably exceeded the resolving power of your telescope. A television set looks clear 10 metres away, but up close you can see the imperfections. Back to top Which eyepiece design is best? This often-asked question is quite irrelevant, as different design's performance varies with different telescopes. Different eyepiece designs have various characteristics. For example, an expensive widefield design is not required for planetary viewing, where the only important thing is maximum contrast. A Plossl or Orthoscopic would probably be best, but almost all designs are good performers on-axis for any f/ratio. Telescopes with f/ratios>10 are quite tolerant of simple low element eyepieces up to 55 deg. A.F., but telescopes <6 are a different matter. Off-axis performance requires powerful correction to properly image the highly convergent beam. Each eyepiece and telescope performs as a system, and their image can only be evaluated as much. Back to top What is Exit Pupil? Exit Pupil is the size of the light beam the eyepiece projects into your eye. Exit pupil can be calculated as follows: Most night-adapted eyes open to 5-7mm, so it's not a good idea to use eyepieces which give an exit pupil much larger than this, as the beam won't fit into entrance pupil of your eye. Back to top Is high magnification better? Only for some objects, although undermagnification is often a problem, even for experienced observers. The penalty for increased magnification is reduced field of view and brightness; faint objects grow fainter as the magnification is increased This is why larger aperture telescopes are so effective on faint objects; they provide enough light to stimulate the eye at high magnifications. For example, a 4-inch telescope will only view a globular cluster effectively at 80X, and it will appear as a blob. A 6-inch will resolve the outer stars at 130X, an 8-inch will resolve further in at 200X. 10 and 12.5-inch telescopes will make them glitter to the core at 300 and 400X. Back to top Which eyepiece should I choose? If brightness is not a factor, choose the eyepiece that will encompass the object, then allow for a suitable backdrop. If you want to know the actual field of view the eyepiece will give (True Field), this can be calculated as: Back to top Why are some eyepieces more expensive than others? When you pay more for an eyepiece you are usually paying for:- Field of view: Eyepieces that have many lenses to correct for the five major aberrations (these aberrations give increasingly worse, the lower the focal ratio of the telescope) have obviously higher costs in lenses and coatings. Eye relief: Using larger, more expensive elements in eyepieces allows for a greater distance between the eye and eyepiece. Coatings: 2-layer multicoatings on both faces of all lenses will typically add 25% to the cost of an eyepiece, but this is absolutely necessary to preserve the contrast of the image when the light has to go through 7-9 lenses. Back to top Why is the image better at the centre of the field? All commercial eyepieces are made with spherical elements, as these are the only type that are easily mass produced. These naturally produce aberrations, which become much worse in highly convergent light beams. There is no way to avoid all aberrations when using spherical elements. Clever eyepiece designers can, however, minimise the objectionable ones and cause others to manifest themselves in an acceptable form. Back to top What is the black spot I see in a low powered eyepiece in my reflector during daylight? A low powered eyepiece in a reflector produces a large exit pupil with a large image of the secondary mirror obstruction. During the day, when the pupil of the eye is small, if the size of the secondary obstruction image approaches the size of the pupil, it will appear as a darkened region in the center of the field. At night, when the pupil of the eye is large, the darkened region is not noticed. Back to top What is the "Kidney Bean Effect"? The "Kidney Bean Effect" is not the same phenomenon as the before mentioned "black spot". In some long f.l or wide angle eyepieces, it is sometimes necessary to move the eye closer to the eyepiece in order to see the edge of the field. Sometimes, when this occurs, parts of the field between the centre and the edge are cut off, as part of the quickly converging beam misses the eye's pupil. This appears to the observer as a giant kidney bean shaped dark region that meandors around the field as head moves. Back to top Which works better? An eyepiece or a Barlow+eyepiece giving the same magnification? The only time the eyepiece alone may perform as well, is on-axis, in a high-contrast application, as the extra optics of the barlow may cause a slight depreciation. Optically, for all other sues, the eyepice+barlow outperforms the eyepiece working alone. The reason? Most of the aberrations caused by positive spherical lenses (Coma, Astigmatism, Curvature of Field and Spherical Aberration) can be reduced and sometimes almost eliminated by introducing a negative system (barlow) which has the same aberrations in negative quantities! Spherical aberration of the system is reduced as the positive spherical aberration of the eyepiece is cancelled by the negative spherical aberration of the barlow. The other aberrations cancel in a similar way! This is one of the eyepiece designer's most powerful weapons, and it is used in most of the shorter focal length ultra-wide designs. Another great benefit of this idea is that the longer eye relief of the longer f.l. eyepiece used with the barlow is retained. Back to top How important it is to get a parfocal series of eyepiece? Parfocal eyepiece sets reduce the amount of refocusing when changing powers, but it is rare when no refocusing is required. Parfocallizing of eyepiece sets is a non-performance factor when choosing oculars. Back to top Do anit-reflection coatings improve light transmission? Yes. Conventional thought seems to be that all the light not reflected is transmited through to the next medium. This is critial to the performance of high-element wide angle designs with many refractive surfaces. Back to top When I'm observing a bright object like a planet, I see an opposing ghost image. What causes that? The ghost image, and it's evil twin, the out-of-focus ghost is caused by internal reflections inside the eyepiece. The only way to eliminate these is to eliminate air-spaces in the eyepieces, as the ghost is caused by a double bounce between two lenses in close proximity. While the ghost is an annoyance, the out of focus ghost is more of an enemy, as it reduces overall contrast of the image, which determines how much detail you'll be able to see. The treatment, if not eh cure, is di-electric multicoating of the lens-facing surfaces inside the eyepiece. Back to top How many eyepieces should I have? Eyepieces are the most critical factor concerning the performance of your telescope, excepting a dark sky. Eyepieces create the image your eye will see, and the right ones will give you the experience that makes amateur astronomy so rewarding. Even the best instrument will never perform to it's potential visually with poor oculars. Since most manufacturers sell their telescopes with inexpensive ones, and since most people selling a telescope keep their good eyepieces, the aftermarket is your best source. Borrow as many as you can and try them out; for every object there will be an eyepiece that works best with your particular telescope. You'll probably be satisfied with 5-8 good eyepieces; and you'll use your telescope much more often with good ones. Back to top I’m trying to collimate my reflector but all I see at the back of my telescope is 3 Phillip’s-head screws. Where are the 2 sets of screws? Your optical tube is probably covered with a metal back plate. The 3 Phillip’s-head screws are there to hold the metal plate in place. Loosen them and remove the metal plate. You should be able to see the back of the primary mirror and 2 sets of screws around it.
About Binoculars How can I choose the right binoculars for myself? The first step is to determine your need. Since there are many models and kinds of binoculars, the best thing is to ask yourself what you need your binoculars for. Are you going to use it for hunting? For sports? For star gazing at night? Once you have determined the type, next thing to consider is your budget. Binoculars are undeniably expensive. Identifying your budget helps in choosing just the right ones for you. However, like any other products, the higher the price is, the better quality the product has. For example, you can’t compare the quality of the results of a fifty-dollar camera to a ten thousand dollar camera right? The same thing applies with binoculars. Nonetheless, you should not fret about it cause there are still not so expensive binoculars that still offer their products at less expensive prices but still you get the best of quality. Another main concern is the optical quality of the binocular. The powers of binoculars solely base from its features. Professionals in the field of binoculars may handle these concerns and assist you further though when you visit sports shops and boutiques. Back to top How far can I see with your binoculars? The question should not be about how far you can see with a given binocular – with only your naked eyes, you can see millions of astronomical objects that are literally millions of miles away. A binocular (or a telescope, for that matter) simply helps you to see more of these objects, and brings them closer than you would see them using only the naked eye. For example, take our 25x100 binocular; this binocular uses 100mm objective lenses that gather approximately 200 times as much light as a young person’s fully-dilated 7mm pupils. It will also bring any object observed 25 times closer than when that same object is observed using only the naked eye – in other words, an object at a distance of 1/4 mile (1320 ft.) would appear only 52.8 feet away. Of course, this is a greatly simplified example and there are many other factors besides objective lens size (aperture) and magnification that affect binocular performance – browse this FAQ to find out more. Back to top What is the "Optical Quality" of binoculars? The optical elements of the binocular are the coated to reduce internal light loss and glare, which in turn ensures even light transmission, resulting in greater image sharpness and contract. Choosing a binocular with good lens coating will translate to greater satisfaction with the product you ultimately select. Lens coatings range in quality as follows: coated - fully coated - multicoated - fully multicoated. Coated lenses are the lowest quality. Fully coated lenses are quite economical and can work well for you, depending on your needs. Multicoated or fully multicoated lenses are both very good choices. Fully multicoated lenses give the best light transmission and brightest images, and therefore the most desirable. Optical alignment requires a durable, rigid housing to ensure precise alignment of lenses, prisms and eyepieces. If the alignment is the slightest bit off, the result will be eyestrain and headaches. If alignment is off by a large amount, double or crossed vision will occur. Prism design and the quality of glass used determines the prism quality. A binocular with a high quality BaK-4 prism will deliver crisp colours and clear, round exit pupils. A lower quality prism delivers dull colours and and exit pupil with squared off edges. Lens quality determines the quality of colour, brightness, contrast and sharpness. Extra-low dispersion glass (ED glass) or fluorite glass are used to proved sharp, brilliant images. To improve brightness and contrast while reducing glare and light loss, anti-reflective coatings are used. For the best detail and contrast, choose a fully multi-coated optic. Back to top Isn't Higher Power better in a binocular? Not necessarily! Many of our customers cannot hold a higher power binocular steady which makes the image jumpy or blurry. Higher power binoculars are generally less bright, have a narrower field of view and can seem less clear because any particulates in the atmosphere (heat, moisture, dust) are also magnified to a greater degree. Ten power (10x) is often the magnification at which you may see too much jumpiness. Back to top What is "Objective Lenses" of Binoculars? The main (objective) lenses of a binocular serve to collect light, thereby enabling the high resolution observation of distant objects. In a quality binocular each objective lens typically is manufactured of two separate glass elements, the so-call crown and flint elements. The refractive specifications of these elements permit the objective lens to image objects free of false colours. A good forty to forty two mm objective is just right for an ordinary binocular. This objective is also preferred for hunting during legal hours. If you prefer a more detailed and visible shot, the larger 50mm to 56mm lens is advisable for hunting during nighttimes. Though a bit heavy and expensive than the conventional 40mm lens, they are still great and functional for your hunting needs. If you are a light traveller, hunting binoculars having 30mm to 32mm objectives are good options. Portability and performance wise, these are good options. A 20mm to 25mm objective is also available if you really want to travel lightly. Back to top What is "Prisms" of Binoculars? Since the objective lenses form images that are both upside-down and reversed left-for-right, prisms are required to invent the primary image. Most commonly, binoculars utilize either Porro prisms or roof prisms for this purpose. Porro prisms give binoculars their familiar zig-zag profile, while roof prisms permit a straight-line design. Either type of prism could be designed BK-7 or BAK-4. Both are economical and highly effective designs. The finer glass in the BAK-4 design is of high density and virtually eliminates internal light scattering, producing sharp and defined images. Back to top What is "Eyepieces" of Binoculars? The larger the aperture, the higher the practical magnification limit. Since more light is collected and brought to focus by a larger aperture telescope, fainter objects can be seen with it than with smaller apertures. Under good seeing conditions when air is not turbulent, a larger aperture objective gives higher resolution, letting you see finer details. Back to top What is "Specifications" of Binoculars? Binoculars are classified as, for example, 10x25mm read "ten by twenty-five millimetres." In this case the binocular is of ten-power ("10x") and includes objective lenses of 25mm (about 1”) diameter. Other binoculars might range from a tiny 3x18mm to giant battleship binoculars that are 40 x 100mm. The "WA" designation after a binocular specification, such as 10 x 25mm WA, refers to the wide-angle design of the binoculars eyepieces; wide-angle eyepieces can increase a binoculars visual field of view by as much as 60%. Back to top What is "Magnification" of Binoculars? Magnification, or power, is perhaps the most misunderstood term in binocular optics. While higher powers can be useful, power by itself does not increase the level of observable detail; image resolution is a function of objective lens diameter and type of prism, not of binoculars power. Higher powers result in images that are less bright and in a binoculars that is more difficult to hold steady in user hands. Power of 7x to 16x are by far the most popular among regular binocular users. Binoculars with magnification above 20x are generally not recommended for use without tripod. Back to top What is "Field of View" of Binoculars? A binoculars field of view is measured in degrees of arc or as field-width (in feet) at 1000 yards distance. Example: The saxon 8x42 WP waterproof roof prism binocular has a field of view 367 ft. wide for an object 1000 yards distance from the observer, yielding a field of view specification of 367 ft. at 1000 yards. Depending somewhat on the observer’s intended applications; wide-angle binoculars are generally well worth the relatively modest additional cost involved. Back to top What is "Eye Relief" of Binoculars? Eye relief, also known as exit pupil distance, is maximum distance between the eye and the eye lens of the eyepiece to see the eyepiece's field stop. (The field stop is the baffle at the image plane that produces the field edge.) Adequate eye relief is a very important factor for comfortable viewing. Eye relief generally decreases as power increases. Low eye relief (less than 10mm) requires you to get very close to the eyepieces, while higher eye relief (greater than 15mm) allows more distance. Eyeglass wearers need a higher amount of eye relief to allow room for their eyeglasses, however- many eyeglass wearers are surprised to find that they don't need their glasses when viewing with binoculars. For many eyeglass wearers, the binocular can replace their eyeglasses. Binoculars users who wear eye glasses for near- or far-sightedness may remove their glasses while observing; the binoculars can fully correct for these eye defects. Observers who suffer from astigmatism, however, may need to wear their glasses to maintain sharp imaging through the binocular. In this latter case choosing a binocular with longer eye relief (15mm or longer) with enable easier binocular observing with eyeglasses. Back to top What is "Lens Coating" of Binoculars? An uncoated optical glass lens or prism reflects about 10% of the light incident on one of its surfaces, allowing only about 90% of the light to pass through. Standard coatings of magnesium fluoride applied to the lens and prism surfaces reduce the level of reflected light to about 4%, and with substantially reduced ghost images of bright objects. More sophisticated multi-coatings further reduce reflected light and can result in total light transmission through a lens or prism of 99% or more. Some saxon models are multi-coated with perhaps the most advanced multi-coatings available, permitting 99+% light transmission and extremely high image contrast. In addition, some saxon binoculars come with ruby coated objective lenses which protect user’s eyes from UV emission. Coated (C) - One or more surfaces are coated. Fully-Coated (FC) - All air-to-glass surfaces are coated but plastic lenses may not be. Multi-Coated (MC) - One or more surfaces are coated. Fully Multi-Coated (FMC) - All air-to-glass surfaces are coated. Back to top What's "multi-coating "? Coatings prevent reflection and scattering of light- which minimizes light loss and offers better image contrast. An uncoated glass surface can lose up to 5% of light transmission due to reflection and scattering. A single layer of anti-reflection coating can reduce loss to about 1.5%. Multiple layers of different anti-reflection coatings can further reduce loss to as low as 0.25%. Multi-coating therefore, provides a higher level of light transmission and image contrast. Back to top What is the difference between multi-coated and fully multi-coated optics? Most quality binoculars have multi-coated objectives and oculars, but it's also important that all internal air-to-glass surfaces are coated (fully coated) or multi-coated (fully multi-coated) as well. Only the highest quality binoculars are multi-coated on all glass-to-air surfaces (fully multi-coated). This costs more, but allows the highest level of light transmission. Coatings are one of the most important factors in determining image brightness. Many budget binoculars have several uncoated surfaces – this is unacceptable, since each uncoated glass surface reflects about 4-5% of incoming light. In the worst binoculars, only about half of the light entering the instrument actually makes it to your eyes. The result is a dim, washed-out image and a poor observing experience. Such binoculars are normally advertised as having “Coated Optics”, and are unacceptable for all but the least demanding uses. The simplest form of coating is a single thin layer of Magnesium Fluoride. This is a good coating, but Magnesium Fluoride coatings lose about 1.5% of light per surface. That may not sound like much, but keep in mind that most binoculars have 14 to 20 optical surfaces that the light must pass through before reaching your eye. That can translate to some serious light loss - in excess of 25% - for a magnesium fluoride-coated binocular. Binoculars with magnesium fluoride coatings on every surface are called “Fully Coated” binoculars, and are acceptable for some undemanding uses, but generally not for astronomy. The next coating level is binoculars with “Multi-Coated” optics – this generally means that at least the inside surface of the objective lenses and one or more surfaces of the eyepiece lenses feature coatings made of multiple very thin layers (hence the term “multi-coated”). A properly applied multi-coating can appear any colour but will normally look greenish-purple, and will transmit between 99% and 99.7% of the light passing through each surface. What this boils down to is that, depending on the number of multi-coated surfaces, a “multi-coated” binocular can have various levels of improvement in light transmission and contrast over a fully-coated binocular. If only a few surfaces are multi-coated, the improvement will be negligible, but if the objectives and eyepieces are multi-coated and only the prisms retain magnesium fluoride coatings, the improvement can be significant. Unfortunately, there are no hard-and-fast rules for determining what constitutes a “multi-coated” binocular, so it’s possible for a manufacturer to sell a binocular that has multi-coatings on only one or two surface, and no coatings on all the others. In this case, you’d be better off with a standard “fully coated” binocular. Beware of inexpensive binoculars where the multi-coating is too thickly applied, as this can actually hurt performance over a Magnesium Fluoride-coated binocular. Also avoid so-called “Ruby-coated” binoculars like the plague. The best binoculars utilize multi-coatings on every air-to-glass surface (including the long faces of the prisms) and are called “Fully Multi-Coated” or “FMC” binoculars. This type of optical coating can transmit 85-90% of the light entering the binocular – which translates to significantly more light reaching your eye than with the lesser coating methods. Watch out for some manufacturers who claim “Fully Multi-Coated optics” but actually use inferior Magnesium Fluoride coatings on the prisms – this is not a true FMC binocular. By there very nature, multi-coatings transmit light better over a larger area of the spectrum for better colour fidelity. Back to top What is the "Armor" of Binoculars? This is not similar with waterproofing. However, it helps protect your most prized binocular from unwanted scratches. Most importantly, armouring also helps protect your binocular in prevent unwanted sounds. Armor may be an option. It is advised however that binoculars have been lost elsewhere when binocular is being set by hunters. Back to top What is "Exit Pupil Diameter "? This is the diameter of the shaft of light coming from the binocular to your eye. It's easy to estimate this based on the objective size and the power. Exit pupil diameter roughly equals objective size divided by power. So for our 15x60mm binocular, the exit pupil diameter would be about 4mm. A larger exit pupil diameter is generally more desirable- especially for astronomical usage, since our eyes will dilate in darkness. The wider the shaft of light, the brighter the image because the light is hitting more of our retina. The reason a high-power binocular has a darker image is because a narrower shaft of light is reaching a smaller amount of retina. Note: Our specifications for Exit Pupil Diameter are from our actual measurements- not the factory published numbers. Back to top What is the "Mini Binoculars" can do? Generally include objective lenses not large than about 25mm (about 1”) in diameter, they are foldable for compactness and ease of transport. Mini binoculars are small, lightweight, and highly versatile in their uses for, a mini binocular. Because of their relatively small objective lenses, however, mini binoculars are not intended for high resolution birding or other nature applications. Example: 7x16 Back to top Will I need a tripod to my binocular? Tripods are pretty much a necessity for large binoculars, especially when used for astronomy. For most people, only binoculars of 11x or less magnification can be used for longer periods of time without a tripod (although even with low power binoculars, the view will be steadier, and more enjoyable, with a tripod). Back to top Why are the "Compact Binoculars" popular? Considered as optical instruments, binoculars are available in different sizes. They come handy in portable models and widely available in today’s market. Owning a pair should be a necessity when you’re fond of the outdoors. If you’re lazy to bring these heavy and gigantic binoculars with you, then a pair of compact binoculars is the best for you. They are lightweight, portable, and easier to carry everywhere you go. Compact binoculars are designed specifically for travelling people who want to avoid the hassle of carrying heavy things and still get almost the same viewing quality as giant binoculars. They are ideally used in hunting, bird watching, travellers, sporting, and those who enjoy the scenery of nature. Ideally, compact binoculars are those that have lenses smaller than 30mm. The concepts behind them is still the same as telescopes except that it has two small telescopes physically attached together. Each telescope contains an objective lens, an exit pupil and an eyepiece. What makes compact binoculars easier to use is that they have smaller objective lens which makes them the top choice for some amateur outdoor enthusiasts. They are also foldable which makes them portable and convenient to store in any container. Like big binoculars, they are also protected with rubber to improve its durability. When you buy a new one, they are contained in a case and will have a hanging strip. Compact binoculars have so many designs to choose from, be it professional or for entertainment purposes like spectator sports, camping, hiking or just about any outdoor activity. There are also compact binoculars for bird watching exclusively. They are capable of providing bright images and wider view and sometimes have night vision and waterproof capability if you’re on a rainy night adventure. These types of binoculars are really an indispensable tool to every outdoor enthusiast. When you are a travelling person, having a portable and light luggage is a must. Whether you’re a bird fanatic, a nature lover, a hiker, or a sports enthusiast, you will need convenient equipment that is not going to give you a hassle. Compact binoculars are one solution to the needs of people who love mobility when they are outdoors. Almost all people would surely want to travel light and having a pair of these small binoculars could mean simply ease in slipping them around one’s neck or put them in small-sized pockets or bags. Compact binoculars is the answer when portability and mobility are required. Since they will have smaller lenses compared to bigger models, the light they collect will be lesser. So it’s important to consider the quality of the optical activity in them. You should read for the manual for the product you’re purchasing such as the quality of the glass used in the prisms and the lenses. Check also for the anti-reflection coatings used together with the optional features like waterproof and night vision. Compact binoculars are very efficient when you don’t really need to look very far. When viewing with them, just try to get adequate light and as much as possible use them in a closed location. These can compensate for the lack of features you can find only in larger binoculars. Smaller binoculars can also work excellently in theatre-viewing or in small sport arenas. You can try out the Bushnell compact binoculars if you want extra-wide viewing area. These smaller binoculars are also ideal for children and beginners who are just starting to embrace the beauty of the outdoors. Upon constant usage of binoculars, you will acquire the experience needed to fully operate them to their maximum efficiency. Utilise Porro prisms or not roof prisms to invert the image and usually are styled to form-fit comfortably in the observer’s hands; objective lenses are typically 32mm in diameter or less. As their name implies, compact binoculars, while larger than mini binoculars, are relatively small and easy to carry. For sporting events, as a gift item, or as a general-purpose travel binocular, compacts are extremely popular, because, again, for all but the most advanced applications, compacts provide a good trade-off between weight, performance and cost. At this point of time, you may think about investing in the best compact binoculars available. If you’re a regular user of giant binoculars, there will come a time you will need smaller ones. If you find something interesting on a day and need quickly out, you may find it convenient to just slip in a compact binocular just about anywhere on your clothes or gear. Your compact binocular could also serve as your backup in case your larger one is out of order. Examples: 12x32 or 8-20x25 Zoom Back to top What do the "Standard Porro Prism Binoculars" can do? Most binoculars referred to as general-purpose are standard Porro prism models. The typically large objective lens apertures, 35mm or more, of these models enable bright, high-contrast images on the entire range of viewing subjects, from sporting events, to long-range animal observation in the wild, to high resolution study of a bird feather structure. A moderately prices, high quality, standard Porro prism model is a binocular for almost any observing application. Standard Porro prism binoculars are available in a wide range of specifications and price points. Examples: 8x40, 10x50 and 20x50 Back to top How do "Zoom Binoculars" work? Offer the convenience of zooming to higher or lower power at the touch of a finger. The 10-30x50 “Triple Zoom” model allowed powers from 10x wide-field to 30x high-power, and with high-resolution imaging and sharp image focus at all magnifications. Most amateur astronomers avoid zoom binoculars due to inherent limitations with zoom optics. Some of the drawbacks are a significantly reduced field of view (compared to fixed binoculars at the same power) and typical use of BK-7 prisms. We used to feel that the advantages and convenience of the zoom feature was worth the trade-offs, but our initial enthusiasm for zooms has decidedly cooled with experience. We agree with the majority opinion of amateur astronomers and do not recommend them to those that are primarily interested in viewing the night sky- fixed-power binoculars are always preferable for astronomy. Nevertheless zooms are quite useful for nature studies, sporting events, occasional night sky viewing, etc. Example: 7-15x35 Back to top What are the advantages of "Standard Waterproof and Porro Prism Binoculars"? It is important to protect our binoculars from rain, dust, mist, moisture, fog, fire, fingerprints or sunrays or just anything that can make binoculars function inefficiently. One of the most common threats is water. The optical surface is very susceptible to water so if you’re planning on using binoculars on moist or rainy areas, waterproof binoculars are highly recommended. Waterproof binoculars are purely resistant to fresh and saltwater. They are specially designed to deliver clear images even after immersed in water. Waterproof binoculars are made in the most strict quality standards. Before they are brought into the market, they are fully tested first if they can endure the maximum harshness of water. Most waterproof binoculars have a lens protector to drive away water from the objective lens and eyepieces to help eliminate glare which are caused by the droplets of water. Lens protectors of these types of binoculars have a special and unique coating to repel water droplets. Next to military applications, hunting perhaps is the second most likely to qualify in the wear and tear group. That is why, it is very vital to have your hunting binoculars waterproof. Whether you are hunting on dry climate or not, it is also important to take note that your binoculars must not fog internally. However, with the latest technologies today, this issue is not needed to be worried about as most of the manufacturers have come up with durable and waterproof products that is guaranteed to withstand to almost all kinds of elements. Special types of these binoculars can float in water for maximum protection. They may also have the latest roof-prism design with coated optics to maintain the sharpness and brightness of images even at worst climates. Optical coatings are sometimes applied to help reduce glare for those wanting the clearest view as much as possible and a rubber armoring also provides a firmer grip to the user. Most people carry around binoculars freely instead of putting them in their case. Luckily, the latest weatherproof binoculars we have today can survive different types of bad weather. To be sure, binocular lens protectors have to be used at times. Lens caps get lost so easily so some have attached lens caps at the binocular. Fortunately, new binoculars coming out today have attached lens cap protectors so they are useable for such a long time at any season of the year. Professional-level binocular resolution and performance are generally reserved for standard roof and Porro Prism models. Designed for advanced applications, such as for serious birders, standard roof prism binoculars are typically of 35mm objective lens aperture or larger; include sleek, straight-line roof prism styling; and incorporate the finest optical glasses, multi-coatings, and multi-element eyepieces. The result is bright, extremely sharp, high resolution images throughout the field of view, and with a level of image fidelity unobtainable in lesser binoculars. Though premium-grade standard roof prism binoculars are not inexpensive, they are usually treasured for a lifetime. Examples: 9x32 or 10x42 Back to top What can "Large Aperture Binoculars" do? There is nothing quite like the view offered by large-objective binoculars. Saxon offers from 60mm to100mm extra large objective lens. The 3-D quality of the stereo image can be breath-taking, and just can not be matched by the “flat” view from a single-ocular telescope. Large aperture binoculars offer phenomenal performance for astronomical viewing. They are also a great choice for terrestrial use, especially from long distances. Back to top What's the difference between BAK4 and BK-7 prisms? BAK4 prisms (barium crown glass) are the highest quality available. BK-7 prisms (borosilicate glass) are also good quality, but sharpness falls off slightly at the edge of the field compared to BAK4. Back to top How to Clean Binoculars? Purchase lens paper and special lens cleaning fluid. Blow hard on one of the lens to get loose debris and dust off of it. Brush the lens off lightly with a piece of lens paper. Wet a lens paper with the cleaning fluid and lightly wipe off the lens. Use a circular pattern. Take a dry lens paper and wipe any wet fluid from the lens. Repeat for the other lens. Use a soft cloth that is barely damp with water to wipe off the exterior of your binoculars. Tips: You can buy lens paper and cleaning fluid at a store that carries camera supplies. Do not use your shirt to wipe the lenses. You may very well scratch them. Back to top Can I use your large-aperture binoculars for terrestrial observation & spotting? Of course! Many of our customers use their Garrett Optical binoculars for terrestrial observation in addition to amateur astronomy, and some use their instruments exclusively for hunting or other spotting applications. We generally recommend that customers wishing to use their binoculars for terrestrial work adhere to the same mounting recommendations made for amateur astronomers, and we recommend 20-25x or less magnification for most terrestrial applications. Large-aperture binoculars are a great substitute for a spotting scope because of the comfort of two-eyed viewing. Their excellent image brightness also makes them ideal for low-light applications. Back to top Can I use my binoculars to observe the moon and planets? Binoculars can offer outstanding low-power views of the moon, creating an impressive "three-dimensional" effect that isn't possible with the single eyepiece of a telescope. However, in larger apertures the moon's brightness can become unbearable, and for this reason many of our larger binoculars are threaded to accept standard neutral density moon filters. Large aperture binoculars utilize extremely fast optical systems, so you can expect some minor flaring and chromatic aberration on extremely bright objects such as Venus and Jupiter (see the FAQ on “false colour” below). Keep in mind that fixed-power astronomy binoculars were designed primarily for observing dim deep space objects, and their magnification is too low to see much planetary detail. If you are interested in primarily planetary observation and still want to enjoy the benefits of binocular observing, you’d be better off with one of our Binocular Telescopes. For casual observing, though, conventional binoculars of 15x-30x magnification can provide nice quick looks at the planets, as long as you recognize their limitations and don’t expect them to perform like an expensive telescope. The amount of planetary detail you will be able to see is dependent on your visual acuity and the magnification of your binoculars. For example, for most individuals the ring of Saturn becomes clearly separated from the disk at around 20x in moments of good seeing, but for some it may take 25x magnification, while others will be able to see clear separation at 15x. Back to top Could large-aperture binoculars offer the same image quality as my premium telescope? Probably not, and certainly not if your telescope is an expensive apochromat. First of all, binoculars operate at much larger exit pupils than are typically used with most telescopes, which means that the natural aberrations in your eyes will become more noticeable on bright objects. Also, let’s consider the economics involved in producing a large-aperture binocular - for a typical, $370 100mm binocular, you are getting (2) F/4.5 doublet achromats, (2) prism clusters, and (2) wide-angle eyepieces, plus premium multi-coatings and all the mechanicals required to bring it all together and maintain collimation. We’re not aware of any $185 100mm F/4.5 achromat packages than come with a high-quality diagonal, collimateable lens cell, and a wide field ocular, but if there were such a package, the performance expectations of any refractor aficionado would be pretty low. The point is that the performance per dollar being offered by most imported binoculars is amazing when you consider the price in telescope terms - that's why large-aperture binoculars are enjoying a surge in popularity – but this does not mean that you should expect the same level of performance on bright stars and planets as you would from a more expensive telescope. If you are looking for telescope-level performance with all the advantages of a conventional binocular, consider purchasing one of our Binocular Telescopes. That being said, when binoculars are used for deep space observation, their large aperture and wide field of view can offer an observing experience superior to that offered by almost any telescope. Back to top What’s the difference between “roof prism” and “porro prism” binoculars? Probably the first thing you will notice about a binocular is its body style. That body style is a result of the type of prisms employed in the optical system. There are two primary prism designs used in modern binoculars – porro prisms and roof prisms. Porro prism designs are the most common, but they are more bulky than their roof prism counterparts. Even though they are slightly larger, porro prism binoculars can actually be easier to hold than roof prism designs for individuals with large hands. Roof prism binoculars feature a sleeker profile than porro prism binoculars, but because of their design the roof prisms must be extremely accurately aligned to produce good performance. Because of this, a given roof prism binocular tends to be significantly more expensive than comparably-performing porro prism glasses. Also, in order to match the performance of the better porro prism binoculars, roof prism designs require expensive phase coatings. Back to top What is the difference between “center focus” and “IF”, or individual focus binoculars, and is one better than the other? There are two different focusing mechanisms are commonly employed on binoculars – center focusers and individual focusing (IF) oculars. For most applications, either design is acceptable; however, in situations where it is necessary to change focus rapidly, such as when birding, the center-focus design is clearly preferable. IF binoculars are often preferred for binocular astronomy, because once adjusted they tend to hold focus well, and IF binoculars can have more diopter range for those who need corrective lenses but prefer to observe without their glasses. Some binoculars, such as our Gemini WP and Signature giant binocular series use individual focusers for precise adjustments, while our Gemini LW and Classic series use the more common center-focus mechanism. Some binoculars, such as our Gemini LW series, utilize specially-designed “slow center focusers” that allow the fine-tuning that is essential for astronomical observations. If you buy a center-focus binocular, be sure it includes a Right Diopter Adjustment (RDA). An RDA allows you to compensate for the differences between your eyes and thus achieve maximum clarity. Individual focusing binoculars do not require an RDA, because each ocular adjusts independently of the other. Back to top What is binoculars “shockproof” for? Don’t be fooled by some manufacturers’ claim that their binoculars are “shockproof” or feature “shockproof prism housings.” This is simply not true – there is no such thing as a “shockproof” binocular. No matter how well a binocular is constructed, it can always be jolted out of optical alignment. That’s why it’s important to treat all binoculars with care - like the precise optical instruments that they are. Back to top What is “light gathering power”? Objective lens size is the factor that determines how much light can potentially be collected by the binocular, and thus how deep you can see in the sky itself. Note that how much light actually gets to the observers eye is dependent on several factors, such as prism, size, baffling, and coating quality. In general, though, given similar coatings, you can use aperture to compare how much light will be gathered by two different binoculars. Because a binoculars’ lenses are circular in shape, the area of the lens is inversely proportional to the lens diameter. In other words, a 100mm objective will gather four times as much light as a 50mm objective, even though it is only twice as far across. Back to top Why does my binocular show distortion near the edge of the field of view, and does this mean that the binocular is defective? Most binoculars utilize extremely fast optical systems with focal ratios of f/4 to f/4.5 or even less. Even the best eyepieces will show some field curvature at these focal ratios, and the standard binocular eyepiece is usually a simple, 4-element wide-angle design. This means that the center of the field of view often comes to best focus at a slightly different focus setting than the edges of the field of view. This produces some flaring and distortion of star images near the edge. In practice, this is rarely a problem since the observer’s eye is naturally drawn to the center of the field of view, and it is natural to move the binocular until the object being observed is in the center of the field of view – this is a completely different method of observing than is used with most telescopes. All binoculars experience distortion near the edge of the field to some extent, but it is usually better suppressed in more expensive binoculars that utilize complicated eyepiece configurations. Back to top What is “phase-coatings”? There is another type of coating process used on some binoculars, called “phase-coating.” Because of their design, roof prism binoculars actually split incoming light into two separate beams as it passes through their prisms. Unfortunately, after they are split, the two paths of light become “out of step” with each other. This in turn affects image quality. Phase coatings are applied to the roof prisms and are designed to re-merge the two paths of light for maximum performance. Because of their sophistication, phase coatings are normally found only on relatively expensive roof prism binoculars. Phase coatings are not applied to porro prism binoculars, because the porro prism design does not suffer from the same deficiency as roof prism binoculars. Back to top What is the "Near Focus" for? Near focus indicates how close (in feet) you can be to an object and still maintain a sharp focus. For birding or nature studies, a near focus of 15 feet or less is recommended. Back to top What are the Focus Types? There are three main focus systems: centre, individual and permanent. The most common system is centre focus. A central dial is used to focus both sides at the same time. Best for viewing moving objects. Individual focus system binoculars are best for viewing slow-moving or stationary objects. Binoculars that have individual system focus are focused by turning each eyepiece. Lower quality binocular models may use permanent focus systems which produce inferior detail and no adjustment for differences in eye strength. Back to top What are the keys for image quality? RELATIVE BRIGHTNESS INDEX: A binoculars ability to gather and transmit enough of the available light to give a sufficiently bright and sharp image defines its brightness. The brightness of a binocular also enhances colour differentiation in the image observed. R.B.I. (relative Brightness Index, Twilight Factor and R.L.E. Relative Light Efficiency are common indices used in the binocular industry, but are all somewhat flawed in their design and often prove fairly meaningless. Simply square the exit pupil - if your binocular has an exit pupil of 4mm, the relative brightness is 16 ( 4 x 4= 16). CONTRAST: Refers to the degree to which both dim and bright objects in the image can be differentiated from each other and from the background on the image. High contrast helps in observing fainter objects and in discerning subtle visual details. High quality optical coatings provide better contrast in an image. The other factors affecting contrast are: collimation, air turbulence, and objective lens, prism and eyepiece quality. RESOLUTION: A measurement of the binoculars ability to distinguish fine detail and produce a sharp image. Better resolution also delivers more intense colour. Resolution varies in relation to the size of the binoculars objective lenses. Generally, a larger objective lens will deliver more detail to the eye than a smaller objective lens, regardless of the optical components, the type and quality of the optical coatings, atmospheric conditions, collimation (i.e. proper optical alignment), and the visual acuity of the user. Back to top Why does only one eyepiece can be adjusted for my binoculars? Because all eyes are slightly different, binoculars feature a Right Eye Diopter Adjustment. The purpose of this is to compensate for slight differences between a person's two eyes. With both eyes open, cover the right objective lens (front) with your hand. Turn the centre-focusing wheel until the image in the left side is sharp. Again, cover the left objective lens (front) with your hand and focus the right side by rotating the right eyepiece until the image is sharp. The binocular is now adjusted to your eyes. Make sure you're looking at the same object when calibrating each eye. Make a note of the diopter adjustment and turn the right eyepiece to that diopter adjustment whenever you look through them. Once you make this adjustment, you do not have to touch the diopter adjustment. Simply focus both sides by turning the centre wheel. If there are multiple users for the binoculars, they will need to be re-adjusted for each user. Back to top

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