We would be surprised at the amount of objects that can be seen with binoculars. We have at our disposal star clusters, some nebulae, the Andromeda galaxy and the entire Milky Way full of stars to explore.
If we want to observe the sky more closely, binoculars offer us that possibility. They are cheaper and easier to use than telescopes.
We recommend not to acquire a telescope as the first piece of equipment of the amateur astronomy. It is true that telescopes offer large increases, but precisely because of this, it is more difficult to find the celestial object that we are looking for. With binoculars it is much easier to locate, thanks to its small increases, the celestial objects. To this we must add that they show the images to the right. That is why we must spend time exploring the sky with binoculars and thus acquire a better preparation to find objects later with a telescope.
We would be surprised at the amount of objects that can be seen with binoculars. If we look for a dark place, we have at our disposal star clusters, some nebulae, the Andromeda galaxy and the entire Milky Way full of stars to explore.
We can also observe Jupiter and its satellites, as well as the craters of the Moon. Comets tend to look better with binoculars, like sun and moon eclipses, and planetary conjunctions.
Magnification of binoculars
There are binoculars of many types and magnifications. In the shop it is convenient that we check the smoothness of the mechanism, the clarity of vision at the edges of the field and how they adapt to our hands and eyes.
The most frequent models in astronomy are the 7 X 50. The first number represents the increases. In this case, it would be 7 increases. There are models that offer up to 16 or 20 magnifications, but such power has its drawbacks: by reducing the field of vision, it is more difficult to locate objects, and the vibration of the hands makes the images appear blurry.
The second number tells us about the opening of the front lenses, in millimeters. In the previous example, 7 X 50, would be 50 millimeters. There are smaller models, 35 or 42 mm. of aperture, but 50mm binoculars or binoculars offer brighter images. This is very important when it comes to finding weak objects in the sky. In stores we can find binoculars with a larger opening, with 60 or 80 mm lenses, but they are very heavy and difficult to hold.
The best choice consists of binoculars of 7 X 50 or 10 X 50. In both cases, they offer a good balance between increases, lightness of the image and lightness. We must avoid fixed-focus binoculars and those with zoom, because they offer insufficient quality images when we want to observe specific objects such as stars.
Large binoculars, of 11 X 70, 20 X 80, 25 X 100, etc., are not a good choice for beginners due to their high cost, since they cost the same as a small telescope, and also because of the difficulty of its management In addition, we must add the purchase of a tripod, indispensable element for binoculars so heavy. Although the fact is that large binoculars offer really spectacular panoramas of the sky and serious observers should consider them as a possibility.
It is very important to consider the ocular relief, which means the distance between the eyes and the eyepieces to see the specific field. If the observer wears glasses to see from a distance, it may be more comfortable to have them on during observation with binoculars. In this case, we must choose binoculars with 18 or 20 mm of ocular relief, at least, and finished in retractable rubber flaps. These models leave a lot of space between the eyepiece and the eye so that we can see the entire field even with the glasses on, and the eye is at the right distance. If glasses are not worn, we extend the rubber flaps so that the eyes are at the correct distance.
The binoculars of 7 increases offer, the majority, a field of 7 degrees, enough to see the box of the Big Dipper. Models of 10 or more magnifications have smaller fields of vision, for example, 5 degrees, still suitable to provide spectacular images of the sky.
There are binoculars that bring marked in the box the field that they cover in degrees, although sometimes they do not give it in degrees, but in meters covered to 1000 m of distance. In this case, the field spanning 1000 m should be divided by 17.5 to obtain the field in degrees.
Some binoculars with wide field eyepieces provide larger fields than normal, can reach up to 7 or 10 degrees for models of 10 magnifications. The bad thing is that in this case, the quality of the image sometimes suffers, and the binoculars show distorted stars at the edges of the field. They also tend to have a rather reduced eye relief. If we look for binoculars that have a comfortable eye relief, wide field and quality images, the price of these is higher.
Types of prisms
We can choose between two types of prisms for binoculars. The Amici prisms make the binoculars H-shaped with straight sides. Porro prisms give binoculars a zigzag or N-shaped profile. Porro prisms are preferable for astronomy. If we buy an economic model with Amici prisms we can get annoying sparkles in the form of points in the bright stars. The ideal ones are binoculars with Porro prisms made of BAK4 glass, which offer better illuminated fields than those produced with the cheaper BK7.
We must also take into account the type of surface treatments applied to the lenses, as well as the number of lenses treated. Treated lenses improve light transmission and contrast. Economical binoculars offer single-layer treatments on the most important optical surfaces, while those with better quality have multi-layer treatments on all optical surfaces. We can see this by looking into the binoculars through the front lenses. If we appreciate internal reflections of white color, it means that this model has lenses with minimal treatment. Some binoculars that have totally treated optics will have few reflections, weak and of green, blue or purple tones.
The more stable the binoculars are held, the better images they will offer. We can appreciate weaker stars and finer details. To make sure, the easiest way is to sit in an armchair and rest your elbows on the arms of the seat with binoculars in your hands. Or better yet, attach the binoculars to a photographic tripod that is solid.
A good tripod offers firmness, but it makes the observation of the highest areas of the sky more difficult. For binoculars of 11 X 70 or more, a tripod is essential, although they can also be used for small models, since we will have better images.