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Other high-power binoculars may have excellent optics, but they can also be, quite literally, a pain in the neck. The Zhumell 20x80 SuperGiants, though, weigh in at just 4.4 pounds, light enough to use comfortably in the field. Still, they are equipped with an integrated tripod mount for use with any standard photographic tripod. That's just in case you don't feel like holding onto your binoculars all the time.
THE ZHUMELL 20x80mm SuperGiant
Other high-power binoculars may have excellent optics, but they can also - quite literally - be a pain in the neck. The Zhumell 20x80 SuperGiants, though, weigh in at just 4.4 pounds, light enough to use comfortably in the field. Still, they are equipped with an integrated tripod mount for use with any standard photographic tripod. That's just in case you don't feel like holding onto your binoculars all the time. High-performance features include: Extra-large field of view with crystal clarity from edge to edge; Ultra-smooth center focus that's easy to operate, allowing you to pinpoint your subject, Right diopter adjustment so you can fine-tune your viewing. Most impressive, though, is the sheer size of the 20x80 SuperGiants. The 80mm objective lens diameter is huge. In fact, you won't find many larger, and definitely not in the Zhumell's price range. Once you try these big binos for astronomical or terrestrial viewing, you won't want to go back to anything smaller. And, given all the Zhumell's advantages, there's simply no reason you'd have to!!
(Tripod not included)*
*If you would like the Zhumell Tripod, let me know, and I will give you a fair price.
Good for Astronomy
70 ft. Close Focus
4.0 mm Exit Pupil
17mm Eye Relief
168 ft. at 1,000 yds. Field of View
Center Focus Type
20 x Magnification
80 mm Objective
20x80 Power X Obj. Dia.
Porro Prism Type
4.4 lbs.Product Weight
Super Powerful Binoculars for Land and Sky
Excellent customer reviews for this top seller
Extra-large field of view
Edge-to-edge crystal clarity
BaK4 prisms for excellent light transmission
Fully multi-coated optics
Easy operating center focus to pinpoint subjects
Right diopter adjustment for fine-tuning
Built-in Tripod Adapter to use with any photographic tripod
Great for daytime or astronomical use
■Extra-large field of view with crystal clarity from edge to edge
■BaK4 prisms for excellent light transmission
■Fully multi-coated optics
■Ultra-smooth center focus that's easy to operate, allowing you to pinpoint your subject
■Right diopter adjustment so you can fine-tune your viewing
Most impressive, though, is the sheer size of the 20x80 SuperGiants. The 80mm objective lens diameter is huge. In fact, you won't find many larger, and definitely not in the Zhumell's price range. Interpupillary distance adjusts from 2.25 inches to 2.75 inches.
Once you try these big binoculars for astronomical or terrestrial viewing, you won't want to go back to anything smaller. And, given all the Zhumell's advantages, there's simply no reason you'd have to.
#1.I received the Zhumell 20 x 80's today, and the binoculars really look great. They're larger than I expected them to be, but for the price, I'm satisfied with them so far. I took them out and tested them by zeroing in on a jet that was flying over. The view was sharp and crisp, as I expected it to be. I saw no hint of double-vision that others have complained about, so it seems the collimation is good on this set. The real test will be when I can get them under the night skies and get first light through them of one of the globular clusters, or any of the other great binocular targets. Of course, I'll have to wait on the cloudy skies to clear before I can conduct any further tests. I've got the binoculars, a standard tripod to mount them on (until I'm able to get a parallelogram-style mount, which I prefer), and now I just need the patience to wait out the clouds, and the return of clear skies.
Newcomers to astronomy often rush to buy the first telescope they see in a department store, and this is perfectly understandable. All the beautiful pictures of celestial objects seen in magazines or in books have this effect on most people.
Unfortunately, after setting the telescope in the backyard and taking the first look at the night sky all the magic is gone. The instrument's narrow field of view and confusing image orientation will soon cause more frustration than fun.
The obvious alternative is to invest in binoculars, which have the advantages of being relatively inexpensive, highly portable and easy to use. The only disadvantage is that the magnification is generally fixed. Zoom models with variable magnification are also available, but for reasons you will find later in this article it is probably better to accept the fixed-power limitation.
Binoculars magnifying 5 to 8 times are ideal for finding the planets, scanning Milky Way star fields, studying star clusters such as the Pleiades and Hyades, and viewing bright comets. The Moon will also prove a constant source of enjoyment; the mountains, valleys and craters are beautifully brought out, and it takes only a few minutes to learn the most prominent features.
How Binoculars Work
To understand the working principle of binoculars, first you need to know a little about telescopes. In fact, this is exactly what binoculars are, two identical telescopes placed next to each other.
At the front of each telescope is a lens, called the objective. Its role is to gather light from whatever it is you're looking at and bring it to a focus in the eyepiece, where the light is formed into a visible image and magnified to take up a large portion of the retina. The magnification depends on the focal length of the eyepiece, and for binoculars it is usually between 5x and 10x.
The image produced by this telescope will be upside down and backwards, but for astronomical viewing this is not a major inconvenient. In space there is no up and down or left and right. However, for watching birds or following the action at a baseball game a right- side-up picture is essential. This is why binoculars use corrective elements between the objective and the eyepiece, called prisms.
Prisms used in binoculars are blocks of glass that function as mirrors, but without a mirror's reflective backing. They come in two models and use different types of glass, and we will
discuss about this later in the article. For now let's just mention their role, that is to bring the light beams from the objective closer together by means of internal reflection, and also turn the image right-side up and orient the view properly left to right.
To better understand the working principles take a look at the image above. It shows the path of the light as it enters the objectives, passes through a set of prisms that turn the image right side up, and finally leaves the eyepieces to enter the observer's eyes. This applies to all binoculars, no matter what model or size.
All binoculars are described by using a pair of numbers, such as 7x50 or 8x30. The first number, including the x, represents magnification or "power". This tells the degree to which the object observed is enlarged. For example, a 7x binocular makes an object appear seven times closer than when viewed by the naked eye.
There are some models of binoculars that offer variable magnification, usually in the range of 5x to 8x. They are
called zoom binoculars, and in most cases are not very suited for astronomical observations because of the inferior optical quality and fragile mechanics. The best thing to do is to avoid them and stick with the usual fixed-power binoculars.
Magnification is not that important, and in most cases comes within 7x to 12x. If the magnification exceeds these figures, most likely you won't be able to hold the binoculars steady enough and the images will be blurry and in constant movement. This is especially frustrating when observing faint objects like galaxies and nebulae. A tripod mount or image-stabilized binoculars will get you rid of this problem, but we will talk about this later in the article.
The second number in the two-number code is aperture (from the Latin aperire - "to open"), the most important specification of binoculars if you plan to use them for astronomical observations. It represents the diameter of each of the objective lenses (the lenses furthest from your eye), given in millimeters. Therefore, 7x50 binoculars have objective lenses 50 mm in diameter.
After all these said, it is clear that when it comes to
aperture bigger is better. The larger the light gathering area, the brighter the images will appear. Compared to the naked-eye a 50 mm binocular gathers from 50 to 100 times as much light, translating into a difference of five stellar magnitudes. Therefore, if from your observing site you can see stars to magnitude 5.5 with the naked eye, the binocular will show many more stars down to magnitude 9.5 or even dimmer.
If you divide the objective lens diameter by the magnification, you will get a number approximately between 4 and 8. This number is called the exit pupil, and represents the diameter of the beam of light that leaves the eyepiece when you hold a binocular with the objective pointed towards a light source. For example, a 7x50 binocular has an exit pupil of 50 divided by 7, just over 7 millimeters in diameter.
Ideally, the exit pupil of your binocular should be equal or slightly smaller than the pupil of your dark-adapted eye. In this way the binocular delivers the maximum amount of light and produces the brightest possible images for its aperture.
Average young adults under dark night conditions have pupils that are open to about 7 millimeters. This means that any instrument with an exit pupil larger than 7 millimeters will only waste light, as only the centre of the light beam could enter the eyes. As we get older our eyes dilate less, so the exit pupil size we need decreases to around 5 millimeters.
Field of View
The field of view is the area of sky or land seen through your binoculars, determined by the design of the instrument's optics. It is expressed in two ways; as the width in feet at 1,000 yards, or in degrees of field. When expressed in feet the field is called linear, and when expressed in degrees it is called angular. Don't let the terms confuse you, the conversion is easy - divide the liner field by 52.35 and you get the angular field.
In most cases the field is indicated on the outside of the binocular, in degrees. Average values are between 5 and 10 degrees, or roughly 260 to 520 feet. To get an actual idea of how wide this field is, think that in five degrees you can fit almost 10 Full Moon diameters!
For astronomy, a wide field of view is desirable because if offers a more pleasant viewing experience,
and you can see more of the sky at a better edge performance compared to a narrower field. However, when increasing the field beyond a certain point images start to exhibit signs of distortion, especially near the edges of the field. Also remember that field of view is related to magnification; the higher the power of your binoculars, the smaller the field will be.
Eye relief is the distance behind the eypice lenses at which the image is in focus, and indicates how far the binoculars can be held from your eyes and still allow you to see the entire apparent field of view. In general, the longer the focal length of an eyepiece, the greater is the eye relief. Standard binoculars have eye relief ranging from only a few millimeters to 25 millimeters or more.
Long eye relief is especially necessary for eyeglass wearers, because glasses increase the distance
between the lens and your eye. In case your eyeglasses correct only for near or farsightedness, you can simply take them off and refocus the binocular to compensate.
Interpupillary distance is the distance between each of the adult person's eyes. Most binoculars are adjustable to accommodate different interpupillary distances, typically within a range of 60 mm to 72 mm. Many children and some women have interpupillary distances too short for standard binoculars, so the only solution is to choose compact binoculars.
Because when using binoculars to observe the night sky you want the biggest possible amount of light to reach your eyes and not be reflected back into space from the objectives, modern lenses have antireflection optical coatings on at least one of the air-to-glass surfaces. Very good models will have all glass surfaces coated, but tend to be more expensive.
The most used and least expensive coating is a single- layer of magnesium fluoride
(MgF), but there are also modern broadband multicoatings. To save money, some optics manufacturers coat only some of the air-to-glass surfaces, and basically we can talk about four levels of coatings used on binoculars.
Coated lenses are the lowest quality, with a single-layer MgF coating on some of the optical surfaces. Fully coated means that all air-to-glass surfaces are coated with a single-layer MgF coating. Multicoated lenses have multi-layer coatings applied on some surfaces, and finally, fully multicoated lenses have multi-layer coatings applied to all of the surfaces.
Recently the market has been invaded with binoculars that have so-called "ruby" coatings intended to reduce glare in bright light and improve the contrast between brown and green objects. Avoid any binocular that uses these coatings, it will perform poorly for astronomical use.
All binoculars are built with prisms that serve as mirrors to reflect the incoming light between the widely spaced objectives and the narrowly spaced eyepieces. They also have the role of inverting the image that the objective lenses project, in a right-side up and not reversed left to right view. Prisms come in two types: roof and porro prisms.
Roof prisms are in line inside the optical tubes, allowing binoculars to be made small and light. This is a great advantage for hikers and birders, but for astronomical use roof-prism binoculars prove to be poor performers.
In roof prism binocular design the light beam is split in two parts, then recombined. This process leads to "phase shifting", meaning that less light is transmitted in the eyepiece and contrast is decreased. Besides, roof-prism binoculars are generally much more expensive than porro- prism binoculars of equal quality.
Porro-prism binoculars align the objective lenses and eyepieces in an offset arrangement, with the objective lenses farther apart than the eyepieces. They offer a wide field of view and are very affordable. However, porro
prisms have a minor drawback: they are easier to knock out of alignment than roof prisms.
Prisms are made of two types of glass, BK-7 borosilicate flint glass and BaK-4 barium crown glass. For most designs, prisms made of BaK-4 are preferred over the standard BK-7 because they have a higher refractive index and give brighter and well defined images.
To check for yourself the type of prisms in your binocular, hold it pointed towards a light source and take a look at the exit pupils. If the prisms are made of BaK-4 glass the exit pupils will be round and evenly illuminated. If the prisms are of BK-7 glass you will notice squarish, gray edges in the exit pupils.
Because binoculars are basically two small telescopes mounted side by side, an error in collimation (optical and mechanical alignment) can lead to numerous problems including eyestrain and double-images.
Most cheap binoculars are shipped out from the factory with collimation problems, and even quality models come out of alignment as they age and get bumped around. The only solution to this problem is to buy binoculars with quality mechanics, which will last longer before collimation errors become a nuisance.
Stabilizing the View
For any binoculars to give their best, they need to be held steady. This eliminates the constant jiggling associated with hand-holding, and allows you to see small details and objects fainter than you might think possible.
The traditional and least expensive mount for binoculars is a simple camera tripod. Most binoculars come with a threaded mounting hole and an L-shaped adapter that screws into this hole and onto the tripod. If you don't receive the adapter when you buy your binoculars you can purchase it separately, or even make your own.
Unfortunately, this type of mounting is difficult to use and tiring for the neck, especially when observing objects near the zenith. The solution is to purchase a commercial mount especially designed for astronomical use, or go for image-stabilized binoculars if your budget allows it.
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