FAQs（Questions and answers of products）

1. Astronomical Telescope FAQ

How to begin with my astronomical telescope?Do I have to be an expert in astronomy to enjoy using a telescope?

Most first-time telescope users know little or nothing about the night sky, and you certainly do not need a course in astronomy to enjoy your telescope to the fullest. Begin with the objects easiest to find: the Moon, Jupiter, Saturn, Venus, and Mars. All of these are bright objects even in the midst of a big-city environment and can be located by using star maps in popular monthly magazines such as Astronomy or Sky & Telescope.

Does you have any hints for beginners on viewing through an astronomical telescope?

For beginners it is best to put in some practice by viewing terrest-rial objects during the day. Initial experience can be gained during this time of the operation and use of your telescope. If your telescope is equipped with a moon filter, be sure to remove it from the ocular, do this before viewing objects and only use the filter(s) for their intended use.

Never mount more than one accessory (except moon filter) with your ocular lens. This shifts your focal length and prevents you from getting a proper focus, (Example: Barlow and Star Diagonal, 2Omm ocular lens.

Let's talk about POWER: It's a natural tendency for all of us to want to magnify the moon, planets and stars as much as possible so as to be able to see it as closely as we can. Wouldn't it be wonderful to see the "canals" on Mars or the ice cap on Jupiter or the Apollo landing sights on the moon?

Yet, the pure and simple physics of light transmission, refraction and magnification through optical lenses make this a very challenging task. As one seeks to increase magnification of an image, more and more of the light is lost or reflected. And as more magnification is achieved, the more interference occurs from ambient or casual light sources, as well as from the atmosphere itself. That is why the more experienced telescope user knows that viewing is generally more enjoyable at lower powers.

That is why we suggest you begin learning about your new telescope by starting at the lower powers. After you gain some skill and practice at low powers, you can carefully move up when viewing conditions are best. By starting with the lowest powered ocular lens, this allows you to focus in and find objects prior to using the higher powered oculars (5mm, 6mm, 4mm or 2x Barlow) produces a smaller field of view. If the image is fuzzy at higher magnification, drop down to a lower magnification as the atmospheric conditions are not sufficient to support the high magnification at observation time. Remember, the higher the number on the ocular, the lower the power. To figure the power of an ocular lens you divide the number on the ocular into in to the focal length of the telescope. (Example: 700mm/20mm=35x). Avoid touching or jarring the scope while viewing. This results in vibration that causes the image to shimmy or move. Also make sure that all assembly screws are secured as tightly as possible. When viewing at night, allow at least 15 minutes for your eyes to become adapted to the dark. If you wear glasses, remove them when viewing through your scope unless you have an astigmatism.

What can i see with my astronomical telescope?

Telescopes with power ranging from 25X to 50X can be used to view Star Clusters and Nebulae. 90X to 120X telescopes can view galaxies. Most planets can be seen at 150X and higher.

How do I determine the power of my astronomical telescope?

The power of your telescope can be determined by dividing the focal length of the objective lens by the focal length of the eyepiece. The eyepiece focal length is the number printed on the eyepiece (for example: 1000 divided by 25=40X).

What do the numbers on the eyepiece mean?

The numbers of the eyepiece represent the focal length of the eyepiece.

What is the difference between a refractor telescope and a reflector telescope?

Refractor telescopes use lenses only (no mirrors or prisms). The refractor is essentially a closed tube design. It is mechanically uncomplicated and basically maintenance free. Refractors are generally used for astronomical viewing; however, they can be used for terrestrial purposes beyond 100 feet.

Why is the image in the astronomical telescope upside down and reverseo from right to left?

An upside down and reversed image is a common characteristic of most astronomical telescopes. Since telescopes are used for astronomical viewing orientation is not important. The image in the finderscope will also be upside down and reversed.

2.Binocular FAQ

What do the NUMBERS mean on a Optical product?

You will see combinations of numbers like 7x35, 8x42, 12x50 or 8-24x50 and many more. The numbers to the left of the "x" refer to how much magnification the Optical product has. The number to the right of the "x" indicate how big the lens is at the bottom of the product (this is called the objective lens). So, 7x35 means this product or magnifies objects so they appear 7 times closer. This Optical product also has a 35 mm diameter "objective lens". A 12x50 binocular magnifies objects so they appear 12 times closer and has an "objective lens" 50 mm in diameter. The 8-24x50 binocular is a zoom model because you can change the magnification from 8 times to 24 times. This binocular has a 35 mm "objective lens". The 30-90x100 spotting scope is a zoom model that you can change the magnification from 30 times to 90 times. This spotting scope has a 100 mm "objective lens".

How much magnification do I need?

You will want a binocular with magnification appropriate to how you plan to use your binoculars. So, think about the demands of your hobby before you select a pair of binoculars. How much detail do you need to see? Will you use your binoculars to view things close up or far away? Will you be able to prop your arms on something for support while using your binoculars? Do I want a small binocular that I can take anywhere?

The most popular binoculars are those with lower magnifications (as with 8x binoculars). These binoculars have wider fields of view and are easier to hold steady than the binoculars with higher magnifications. A wider field of view is important when trying to follow fast-moving action like game on the move, warblers on the wing, or athletes at a fast-pace sporting event.
Higher magnifications (as with 10x binoculars) will give you more detail, but are more difficult to hold steady than binoculars with lower magnification. Binoculars with higher magnification also have narrower fields of view. While many people choose to use 10x binoculars, they are deciding that image size and detail is of greater importance to them.

How to adjust binoculars?

Our left eye and right eye can be different in their vision and focusing capability. Therefore, to use binoculars properly, we must compensate for such a difference, and centre-focusing binoculars have an adjustment mechanism to achieve this. You can find that almost all the binoculars listed in our store have one eyepiece (usually the one on the right-hand side) which is independently adjustable with a marked scale.
To adjust binoculars, first, use a lens cover or your hand to cover the right objective lens which is on the same side as the adjustable eyepiece (note: better to keep both eyes open to avoid distortion by squinting). Look through the binoculars and use the central focusing mechanism to focus on a distant object until it is sharp and clear.
Second, transfer the lens cover to the other lens on the left, again with both eyes open, but this time adjust the focus on the same object using the adjustable eyepiece only, until it is clear. Your binoculars are now properly focused for your use. Adjust the distance between the two eyepieces so that they in the centre of your eyes (i.e., when the two cycles merge into one). You can now use the central focusing mechanism to focus on objects at different distances, but you should keep the adjustable eyepiece at the same focus setting unless it is accidentally moved or the binoculars have been used by someone else.

What about the light gathering ability of my binocular?

Your eye is uniquely designed to gather more or less light as conditions change, but your binoculars are not. Since the light gathering ability of a binocular is fixed, it is important to select a model that best meets your eyes need for light as viewing conditions grow darker.
The exit pupil is the magnified image in the eyepiece as it leaves the binocular to enter your eye. It is an indicator of how well you will see an image through your binoculars on a bright day, at twilight or at night. Almost all binoculars gather more light than is needed by your eye for viewing in bright conditions. For the best viewing at twilight, you’ll want a binocular with a minimum exit pupil of 4mm.

What are lens coatings for?

An uncoated optical glass lens or prism reflects about 10% of the light incident on one of its surfaces, thus allowing only about 90% of the light to pass through. Nowadays most binocular lenses are coated with invisible coverings that work to improve the amount of light transmitted from the front lens to the eyepiece. Standard full coatings can reduce the level of light reflection to about 4% or lower; and more sophisticated multi-coatings can ensure 99% or more light transmission through the lens and prism.

How do I clean my binoculars?

Use common sense in the care and maintenance of your binoculars. Always attempt to blow off any visible dust or dirt from the binocular lenses before brushing or rubbing anything on the glass of your binocular. Next, use a lens cleaning tool like a Lens Pen or lens cleaning tissue to gently wipe off any remaining marks or spots from the lens of the binocular.
Remove stubborn things like dried water spots from the lens of a binocular by lightly fogging the binocular lens with your breath. If your waterproof binoculars are badly soiled, you can even clean them by placing them under lightly running water.

Do my binoculars need to be waterproof?

Binoculars are used outside in all kinds of weather. If you expect that you will be using your binoculars in rainy, wet weather (or if you use them around water), consider a pair of waterproof binoculars. You´ll pay a bit more for this feature, but you´ll also be able to use these binoculars without fear of repairing or replacing them just because they got wet.
Waterproof binoculars are literally submersible and any water damage would be handled under the manufacturers warranty for the binocular.

What if I wear eyeglasses while using my binoculars?

Many models of binoculars will allow you to view in comfort while wearing eyeglasses or sunglasses. These binoculars have been designed to provide you with longer eye relief.
Eye relief refers to the distance images are projected from the ocular lens to their focal point and can vary from 5mm to 23mm. If you want to use your binoculars with eyeglasses or sunglasses, look for binoculars that offer at least 15mm of eye relief.

What is centre focus?

Binoculars with centre focus system use one knob in the middle of the binoculars to move both lenses for fine focusing precision. This allows you to follow the action and switch from one object to another quickly. Binoculars with centre focus normally have one eyepiece (often the one on the right-hand side) which is independently adjustable to accommodate any difference between the two eyes.

How much should I spend on binoculars?

Buy the best quality binoculars you can afford. This will allow you to spend the greatest possible time with your binoculars pressed to your eyes. You´ve probably heard the old statement about fishing that says "to catch fish, you need to have your line in the water". Well, you won´t see more detail unless that binocular is at your eyes. Poor quality binoculars usually spend a lot of time just dangling from the neck.

How to choose an ideal pair of binoculars?

Choosing a right pair of binoculars would very much depend on your main purpose of use. Here are some examples:
If you are looking for a handy pair of binoculars to carry around easily in your handbag or in the pocket, and to use it in numerous occasions such as stadium sports, indoor or outdoor concerts/plays, travel and birding, and you also want to keep the cost down, you may choose a compact model such as 8x21, 10x25 or 7X28 compact binoculars. Such a model has all the functions required for these purposes and they are light in weight. These products have a unique feature with new optical coating technology which greatly reduces light reflection over a wider spectrum and increases image sharpness.

I am an eyeglass wearer, how can I see better through my binoculars?

Most Visionking binoculars are fitted with rubber eyecups that can be 'rolled down' for improved field of view with glasses.

3. Spotting scope FAQS

What is spotting scope?

Spotting scope is an optical instrument used to view distant objects primarily on land - therefore optimized for terrestrial observations. Most spotting scopes are look and work just like small telescopes with refractor, Maksutov, or catadioptric optical design. Normally spotting scopes have 50mm to 80mm objective lens and magnification anywhere from 15x to 60x, but there are more powerful spotting scopes with higher magnification and larger objective lens to 90mm and up.

What’s the difference between Spotting scope and Telescope

From the point of view of the design, a spotting scope and a telescope are not very different altogether.

Both are used for magnification and are constructed with an eyepiece lens and an objective lens. Both are used to be able to see long distance images clearly. Both the spotting scope and the telescope are designed in such a way that they can be mounted on tripods. However, this is where the differences arise.

The basic purpose of a spotting scope is to observe terrestrial targets, whereas that of a telescope is to study celestial objects. Spotting scopes are lighter to make them portable and are armed with rubber reinforcements. They also sport a more ergonomic design, as compared to telescopes, and are more rugged and durable. As compared to an astronomical telescope, a spotting scope has lesser magnification and a smaller aperture. However this enables the spotting scope to have a wider field of view.

Telescopes are optimized for being placed at one place and hence tend to be heavier than a spotting scope. A major difference between the two is that spotting scopes are designed to be mounted on generic camera tripods while telescopes require special mounts, which are quite expensive, to support them. The image produced by a telescope is always inverted and a spotting scope always produces a right side up image.

How to decide whether to use a telescope or a spotting scope? As mentioned earlier, a spotting scope is meant for terrestrial observations. Typically, when there is a need for high magnification, a spotting scope is chosen over a pair of binoculars. Due to the wider field of view that spotting scopes offer, as compared to telescope, they are better suited for observing moving targets. This makes them ideal for birding, hunting, surveillance etc. Spotting scopes are also used with guns for targeting. They can also be paired with a camera to shoot pictures of distant objects. In fact a spotting scope can also be used for star-gazing but will not provide as much clarity as a telescope would.

Astronomy telescopes are far better suited at observing stationary objects due to their narrower field of view. Also, due to their greater aperture and magnification than a spotting scope, they are suited for viewing objects at great distances such as stars, planets and the Moon. Although a telescope can be used to view terrestrial objects, it is not a recommended practice as not only is a telescope bulky but also produces an inverted image.

Do I need to buy a special tripods for my spotting scope?

You cannot handhold a spotting scope due to its high magnification. It must be supported to steady it. You can get by at lower magnifications with a monopod or shoulder stock, but above 40x, you must use a tripod and the larger and heavier the scope, the larger and heavier the tripod should be. A car window mount is a viable option for a portable scope, though, if you are observing from a vehicle.

There is no need to buy a special tripod for a spotting scope. All spotting scopes are threaded like a camera and will fit on any standard camera/video tripod.

Can I use Visionking Spotting Scopes and camera to take photos?

Yes. But you need to buy a camera adapter.

What is ED glass in a spotting scope?

ED glass means Extra-low Dispersion. As you know, if you make a prism and pass light through it, it will break white light up into its component colors. The blue end of the spectrum is bent the most, and the red end is bent the least. The prism disperses or spreads out the colors that make up white light.

Dispersion is a simply a measure of how much the colors are spread out by the prism. A typical achromat is made of a low dispersion crown glass and a high dispersion flint glass. The recent advent of extra low dispersion materials, often called fluor-crowns, allows opticians to make two element lenses from a fluor-crown glass and a crown glass. So ED glass help correct chromatic aberrations, or optical color defects, caused when different light wavelengths do not converge at the same point after passing through optical glass. Calcium fluorite crystals were once used to correct this problem in telephoto lenses.

How to buy a Spotting scope

Before you buy, know how you want to use it, as well as the possible distance. By knowing exactly what application you want to use a spotting scope for, you can shop exclusively for the features you need, while preventing yourself from getting overburdened with the cost of extras. It is also important to note that many varieties of spotting scopes are camera adaptable, so you can photograph objects outside the range of your camera lens. These camera-mount scopes require specific mounting components; shopping for your model of camera is as important as shopping for the scope.

1) Spotting scope coated optics:

A coating on a spotting scope not only makes it perform better and deliver better images but also lengthens its lifespan. A coating on the lenses decreases the light reflection to a minimum thereby producing better images. The kind of coating depends on the quality of the spotting scope. A good spotting scope has lenses made of ED glass that eliminates all possibilities of chromatic aberrations. The coating can be of a single layer on the lenses or on all the external surfaces. The coating can also be multiple layered on the lenses or on the external surfaces.

2) Spotting Scopes - Exit Pupil:

The exit pupil refers to the size of the column of light that exits a spotting scope. The larger the exit pupil, the brighter the image. The higher the magnification on your spotting scope, the smaller the exit pupil and the dimmer the image that you see through your scope. To determine the size, divide the objective lens diameter by the power (a 15x45 model has an exit pupil, or useable light, of 3mm).

3) Spotting Scopes - Eye Relief:

The distance a spotting scope can be held away from the eye and still present the full field of view. Extended or long eye relief reduces eyestrain and is ideal for eyeglass wearers.

4) Spotting Scopes - Field of View (F.O.V.):

Field of view of a Spotting scope is the side-to-side measurement of the circular viewing field or subject area. It is defined by the width in feet or meters of the area visible at 1000 yards or meters. A wide field of view is better for following fast-moving action or scanning for wildlife. Generally, the higher the magnification, the narrower the field of view.

5) Spotting Scopes - size, Weight, Mounting:

Size and weight are not optical characteristics of a spotting scope, but if you spend a lot of time in the field hunting or birdwatching, you will appreciate a compact, light weight spotting scope that is easy to carry around.

For any high power observations (normally optical magnification 12x and up), we usually recommend a quality tripod to hold the spotting scopes steady! Most if not all of the spotting scopes we offer come with a built-in 1/4"-20 thread tripod adapter that allows them to be mounted onto any standard camera tripod that we have plenty of.

6) Spotting Scopes - Spotting scope magnification (Power):

Spotting scopes are often referred to by two numbers separated by an "x". For example: 15-45x60 or 15-45x60mm. The first number is the power or magnification of the spotting scope. With a 15-45x60 variable power spotting scope, the object being viewed appears to be 15-45 times closer than you would see it with the unaided eye. For long range observations, in addition to power, make sure to look for larger objective lens so enough light is coming through to support highly magnified image.

7) Spotting Scopes - Near or Close Focus:

The closest you can be to an object and maintain visual clarity. For birdwatching you normally want close focus. For target shooting and hunting close focus in normally less important.

8) Spotting Scopes -Objective Lens size (Aperture):

The second number in the formula: (15-45x60)60 is the diameter of the objective or front lens. The larger the objective lens, the more light that enters the spotting scope, and the brighter the image. For low light conditions (hunting, late night / early morning observations) a larger spotting scope will give you a brighter picture given that the quality and design of the scope is the same.

9) Spotting Scopes - Prism Glass:

Most optical prisms are made from borosilicate (BK-7) glass or barium crown (BAK-4) glass. BAK-4 is higher quality glass yielding brighter images and high edge sharpness.

4. Night Vision FAQ

What is a Night Vision Device (NVD)?

Night Vision Devices are electronically enhanced optical devices that enable us to see in near-total darkness.

What is the Minimal Amount of Light Required to Operate an NVD?

The threshold of vision with an NVD can vary with different "generations", the quality of the devices, distance and the environment. A Generation-1 Night vision with 500x amplification will give a very useful image in the dimmest light of a scarcely visible new moon. From 100 feet, you can distinguish between kinds of animals, whether a human figure is familiar, male or female. While the screen images are not as sharp as a photograph, Night Vision Devices are astonishing in what they accomplish. System amplification of most second-generation Night Vision Devices is around 22,000 times!

What is the difference between night vision generations?

The key difference between the night vision generations is the intensifier technology. Gen. I Night Vision devices use an intensifier tube that amplifies ambient light by accelerating electrons and striking a phosphor surface just like a Television. Generation II night vision devices add a micro-channel plate that multiplies the number of electrons before they impinge on the phosphor screen, thus increasing gain; Generation III Night Vision goggles, monoculars and scopes further add a Gallium Arsenide photocathode which creates significantly more photoelectrons than Gen II night vision devices. Generation IV Night Vision is now offered by ATN. Generation II and III night vision devices offer greater light amplification, they are definitely better than Generation I, but a price beyond the reach of most buyers. Modern Generation I Night Vision devices are high quality and provide light amplification adequate for most recreational activities camping, hiking, fishing, boating, and nature viewing, and for many professional uses such as surveillance, search and rescue, and property management.

Why use a Night Vision Device Instead of a Flashlight?

Two reasons: 1) Night Visions Devices make possible a quality of seeing that is far superior to flashlights. They provide your eyes with a light amplification tool that gives you much more night vision sensitivity than many nocturnal animals. 2) See, without being seen. Think of the advantages of seeing without intruding when you are trying to find your way around an unlit campground. Property owners can observe nocturnal criminal activity. Hunters and nature lovers can observe animals without startling them. If you suspect a prowler is nearby, you can spot the "perpetrator" without alarming him and safely call the police.

How dose night vision work

1. Available light (energy) is collected by the objective lens and focused on the image intensifier.

2. Inside the intensifier a photocathode is "excited" by the light and converts the energy into electrons.

3. The electrons accelerate across an electrostatic field inside the intensifier and strike a phosphor screen (like a monochrome TV screen) which emits an image that you can see. This acceleration of electrons provides gain and enhances the image

How do Night Visions Devices Operate?

Night vision optics are similar to video cameras. Instead of focusing the image on the film plane or CCD (video chip), the objective lens focuses the image on one end of a light intensifier tube. There it is turned into electrons, amplified, and accelerated past a field-forming electrode to a phosphor-covered screen where the image is inverted and focused by static electricity. The phosphors glow brightly where struck by electrons, the same principle by which fluorescent lights brighten a room. The observer looks at the screen through an optical eyepiece or eyepieces and sees the image.

Can I use my Night Vision Devices in the Rain?

Night air conditions frequently include fog and high humidity. NVD's can sustain damage from constant humidity or immersion. Avoid getting them wet, wipe them off with a soft dry towel after use, and store them in dry place without temperature extremes.

What Can Second-Generation Night Vision Devices do That First Generation NVD's Cannot?

They have about 45x more light amplification and, as stated above, they produce about 20% better resolution. The great price difference between the two generations is hard for most consumers to justify, but it is a result of the addition of a porous, coated glass screen called a "microchannel plate". Under most circumstance, there is little practical difference in results between second-generation and first-generation units of equal quality.

Is the magnification of night vision the bigger the better？

No，NVD are primarily intended to make it possible for you to see in the dark, not to magnify distant objects or see objects far away.

Can Night Vision Devices be used during the day?

No. Most of the devices contain highly light sensitive components. When exposed to sunlight, they might get damaged. Some devices are delicate enough to be damaged by bright streetlights, headlights, or even flashlights. The phosphor screen and the light intensifier tube are the units that suffer damage through exposure to intense light.

Do Night Vision Goggles Create Colored Images?

No. All devices for night vision are monochromatic. You see images in green color because thats what the phosphor screen glows with. Green is the color to which human eyes are the most sensitive

What If The Device Slips Off The Hand And Falls?

It will break! The phosphor screen and light intensifier tube are delicate parts that need to be handled with extreme care.

IS It alright to see black Spots on the device screen?

Yes. The image tubes of such devices show spots to some extent. This is one of the inbuilt characteristics of all night vision tools. However, the black spots should remain constant. They should not multiply or get bigger. There is a tolerance limit for these spots for which the devices are tested before being marketed.

Is it alright to see black Spots on the device screen?

Yes. The image tubes of such devices show spots to some extent. This is one of the inbuilt characteristics of all night vision tools. However, the black spots should remain constant. They should not multiply or get bigger. There is a tolerance limit for these spots for which the devices are tested before being marketed.

How far can you see with a first generation night vision device?

There are several different variables that play a role in how far you can see.

1) The amount of light available: When the moon is full and the stars are shining, you will be able to see wild animals as far as 180m away; half moon, only 130m away; only stars, only 80m away and a on a cloudy, overcast night, only 65m away.
But then, a major difference between an ordinary pair of binoculars and a night vision device is that a night vision device is not primarily intended to magnify objects you are looking at or look at objects far away, but to enable you to see in the dark; and they're good at that.

2) How big is the object you're trying to see? Obviously, watching an elephant at 100m is easy; watching a little duiker at the same distance is quite another matter.

3) The environment itself: Dense vegetation and trees soak up light, restricting the light available for your night vision device.

4) The quality of the device you have: As said above, quality comes at a price. The more you're willing to pay, the better the image you will see - no question about that.

How should I care for my Night Vision device?

The number one damage factor is using the device in bright light. Exposure will shorten the life span of a night vision device.

1) Exposure to rain, fog, or even extremely high humidity may damage night vision devices. Built for use at night, they can withstand short exposure to dampness or high humidity conditions.

2) Night Vision devices have delicate vacuum intensifier tubes that are sensitive to impact and should be handled carefully.

3) Clean lenses the same way you would your camera. The lenses are optically coated and may be scratch if abrasive material is used or if dirt is rubbed into the glass. Usually there is no need to remove the lenses and clean inside.

4) Storage for long periods is best in a cool dry place with the batteries removed.