Binoculars with tripod
Binoculars come in a wide range of sizes and designs. This is because they are used in an equally wide range of applications, from watching operas and concerts to bird watching; from hunting to battlefield patrolling; and from sightseeing to stargazing.
Stargazing often requires binoculars equipped with objective lenses that are at least 50 mm in diameter. This is because smaller lenses cannot gather enough light into the optical tube to produce a clear and sharp image. Indeed, for the observation of celestial bodies, binoculars with 125 mm objective lenses are better suited. These are big and heavy equipment, often classified as giant binoculars, that require tripods for smooth and comfortable use.
Tripods are three-legged stands used to stabilize and support optical devices such as binoculars, telescopes, and cameras. They are also used to support surveying equipment such as transits or compasses.
There are several types of binocular tripods. These are the full-length lightweight, compact, table-top, and traveling types. They are usually made of lightweight materials such as aluminum or carbon fiber, but sometimes they can also be made of wood. A center post serves as a brace for the legs of the tripod for sturdier support. The legs themselves are collapsible, with one end telescoping into the other. The feet are usually cased in rubber to prevent them from sliding on slippery surfaces.
Binocular tripods come in three basic designs:
1) Altazimuth Tripods. An altazimuth, or alt-azimuth, tripod features a mount that has two perpendicular axes. These are the horizontal (altitude) axis and the vertical (azimuth) axis. This simple designed is used by home and field users as well as amateur and professional astronomers who work with huge research telescopes. A major drawback of this design is that it cannot follow the apparent movement of celestial objects in the sky with a single motion on its axis. The altazimuth mount has to be moved in its two axes to follow such movement in the skies.
2) Dobsonian Tripods. These are a variation of the altazimuth tripods. Invented by the amateur astronomer John Dobson, this design is suited for visual astronomy. It is made of wood with a simple and inexpensive construction.
3) Equatorial Tripods. Equatorial tripods carry a mount that has two perpendicular axes. These are the right ascension and declination, which allow the binoculars attached to the tripod to follow the apparent motion of any celestial object across the sky with only one motion.
Night Vision Binoculars
Amateur astronomers study the heavens as a hobby relying mostly, if not exclusively, on optical tools, since they do not have access to hi-tech equipment that measures infrared or ultraviolet radiations. They use either a telescope or binocular depending on the kind of heavenly image they want to study.
The most common celestial bodies observed by amateur astronomers are the moon, stars and star clusters, planets, galaxies, comets, nebulae, and meteor showers. Since these are better seen at night, their optical equipment must be suited for low-light conditions. Telescopes are often used, but for certain purposes and under certain conditions, binoculars are a better choice.
One of the main advantages of binoculars over telescopes is their wider field of view (FOV). When studying star clusters or widely dispersed meteor showers, you will want an FOV wider than what most telescopes can offer. Another advantage of the binoculars is their ease of use and portability.
You will want a binocular that can pick up images even in surroundings with very low-light. The three factors that can give your binocular this capability are:
- Prism type. Porro prisms, named after their inventor, Ignazio Porro, are deemed better than roof prisms in terms of gathering light. The type of glass used for the prism is also important. BAK-4 type is often preferred over BK-7 as it offers superior quality.
- Objective lens diameter. With a bigger lens diameter more light will be able to pass into the optical tubel, thus providing a clearer image. You may need a minimum of 50 mm for good nighttime observations.
- Exit pupil. If you hold your binoculars at arm’s length, you will see a circle of light in the eyepiece. That is the exit pupil. Its diameter is determined by dividing the objective lens diameter by the magnification. This opening controls the amount of light coming out of the binoculars. If it is larger than the pupil of your eyes, some of the light will fall on your iris, and thus will remain undetected. On the other hand, if it is smaller, you will perceive the image as dim because only a portion of your pupil will receive light. Therefore, since most astronomical observations occur at night, and since your pupils dilate when it is dark, it is advisable to choose a binocular with a wide exit pupil. Indeed, an exit pupil of at least 7 mm is recommended for nighttime viewing. You can get this measurement from a 7×50 mm binocular.
Most amateur astronomers consider a 7x magnification sufficient for their hobby. However, magnifications of up to 30x coupled with a 60 mm objective lens are also available for binoculars. This increase, however, comes at the price of portability and handiness.
Binoculars and telescopes are not rivals when it comes to observing the skies. They have their own roles to play and they actually complement each other. If you can afford to purchase only one of these fine optical tools, God bless you. That is a very difficult choice.
