What Advantages do Binoculars have over Telescopes in Stargazing?

Advantages of Binoculars over Telescopes in Astronomy
Image Credit: space.com

So, this year you are going to give yourself the shiny telescope you have been wanting for the last two or three years. You have never owned a telescope before but having re-prioritized your budget, you have decided that you can get a decent sized scope that will last you for many years to come. You have also done some research, and you have money available for additional eyepieces, some solar, nebula, and other filters, and even a decent mount and tripod.

However, at this point, we would advise you to postpone your shopping trip until after you have read this article, and here is why. If you are new to the hobby of stargazing from your backyard, you may very well end up being hugely disappointed because what you will see through the eyepiece for the first time will look nothing like the spectacular pictures of nebulae, star fields, and globular clusters you have been drooling over on astronomical websites and in magazines. In fact, you may well see nothing at all and end up packing your shiny new telescope away, never for it to see starlight again.

The purpose of this article is not to discourage you from buying a telescope. Far from it, we are only trying to discourage you from buying a telescope before you have learned your way around the sky, and certainly, before you have learned at least some basic observing skills, for which a pair of plain 7×50 binoculars is the perfect instrument.

However, considering the table below, it might sound counter-intuitive to want to use a pair of binoculars instead of a telescope,

Objects visible with the naked eye Objects visible with 7×50 binoculars Objects visible with small telescopes
5 planets 7 planets 8 planets + Pluto
2-3 galaxies Several galaxies Hundreds of galaxies
± 3 000 stars ± 100 000 stars Millions of stars
A few double stars Dozens of double stars Hundreds of double stars
A few star clusters Dozens of star clusters Hundreds of star clusters
A few nebulae Several nebulae Dozens of nebulae
Planets as point sources Several planets as disks,
moons of Jupiter
Moons of several planets,
surface details of some planets
Milky Way as hazy band Star clouds and dark nebulae in Milky Way Fine detail in Milky Way
Biggest lunar features Hundreds of lunar features Thousands of lunar features

..because who after all, would prefer to see only a few star clusters with binoculars, when there are hundreds of star clusters in the sky that can be seen with a telescope? There are many possible answers to this question, and while some are highly technical in nature, most revolve around affordability, ease of use, and the fact that the field of view offered by a pair of binoculars is at least six times bigger than that offered by a telescope. All of this is saying a lot, so let us address the main advantages of binoculars over telescopes (as they pertain to novice observers) one at a time.

7×50 binoculars gather more light than a 50 mm telescope

The purpose of optical instruments is to gather light, which is then magnified by an eyepiece to form an image of the object being observed. In our example binoculars, the figure “50” indicates the diameter of the objective (front) lenses, while the figure “7” indicates the amount by which the image is magnified. The same is true for larger instruments; the bigger figure always indicates the diameter of the objective lenses, and the smaller figure always indicates the amount of magnification.

Thus, since binoculars are essentially two small telescopes mounted side-by side, a pair of say, 7×50 binoculars, gathers twice the amount of light that a 50 mm telescope does, since the telescope gathers light through only one 50mm objective lens or mirror.

The practical advantage of this that many objects such as most star clusters, many nebulae, and particularly comets, appear much brighter in binoculars than in any other optical instrument of a similar size or aperture because of the lower magnification factor. In addition, the rich detail in the Milky Way appears much brighter in binoculars than in small telescopes because the binoculars gather twice the amount of light. Consider the practical effect over-magnification has on many objects as shown below.

Crab Nebula Magnified
The image above shows the Crab Nebula (circled in blue) as it might appear through low-power binoculars in the left frame. The same nebula is shown in the frame at right (also circled in blue) as seen through a small telescope at high magnification. The reason why the nebula is nearly invisible in the right-hand frame is that at higher magnifications, the available light is spread out over a larger area, which has the practical effect of darkening the background.

Below is another example of how magnification affects the quality of the visible image.

Moon magnification

The Moon is usually very bright and not much magnification is needed to see major features with small instruments. However, eyepieces used on small telescopes generally have minimum magnifications that are much higher than binoculars have, which results in dimmer views of bright objects. In this case, almost the whole Moon is visible through a pair of 7×50 binoculars, while the image on the right is of the same area, but at higher magnification. The result is a darker, less sharp image.

Binoculars provide better context

Field-of-view
Image Credit: SkyNews Magazine

One of the biggest challenges faced by novice stargazers is “learning the sky”. However, this is sometimes easier said than done, given that most telescopes produce images that are upside down or mirror-reversed, depending on the scope’s design. Add to this the fact that star charts have to be mentally reversed or turned right side up before they match the view seen through the eyepiece, and “learning the sky” becomes a steep learning curve that many newcomers to the hobby never master.

Binoculars remove this problem because they show the sky the way it really is. Nothing is upside down, mirror-reversed, or inverted, but the biggest advantage binoculars have is that they show a much larger piece of the sky than telescopes do. The image immediately above shows a view of the Pleiades Cluster (M45) centred over an orange circle, which represents the typical 1-degree field of view offered by most telescope/eyepiece combinations. By way of comparison, the blue circle represents the typical 6-degree field of view offered by most binoculars.

In practice though, finding the Pleiades does not require much “star hopping”, which is the process of following a “trail” of stars and/or other objects to arrive at a particular object that is difficult to find otherwise. Nonetheless, by seeing a 6-degree wide chunk of sky that is right side up, as opposed to a 1-degree wide chunk that is upside down, or worse, mirror-reversed, provides a better context against which to observe an object’s surroundings, which in turn, takes almost all the guesswork out of star hopping.

Binoculars are much, much easier to use than telescopes

While some telescopes, such as Dobsonian reflectors do not require complicated setting-up procedures, others types, and particularly GO-TO scopes have intricate mountings that have to both level and aligned with the North Celestial Pole before they will track objects accurately.

Learning to do this (after having lugged a heavy instrument, its mount, and a tripod down the garden path) represents a steep learning curve in itself, and that is even before you catch a glimpse of the heavens through the eyepiece. By way of contrast, a pair of binoculars has only one, or at most two, adjustments, both of which can be accomplished in three seconds or less. Moreover, binoculars don’t have to be polar-aligned; you simply point them at the sky, and start observing.

Binoculars are much, much cheaper than telescopes

While it is true that some binoculars are very expensive, most middle-of-the road binoculars that work for bird watching will also work for stargazing, especially if you are not immediately interested in hunting down “faint fuzzies” (faint extended clusters) or trying to split close double stars.

While most medium-sized telescopes can show relatively faint fuzzies and split many close double stars, making the most of a telescope requires not only more than a passing knowledge of the sky; it also requires a collection of eyepieces and filters that can collectively, cost more than the telescope itself did. With that said though, all experienced telescope users will agree that a large part of the enjoyment of observing the heavens with a telescope derives from the fact that they know what they are looking at.

In practice, this means that experienced telescope users have learned to manage their expectations. For instance, they know that a view of the say, the Ring Nebula (M57) in Lyra though their 10 or even 12-inch aperture instruments can never look like an image of the same object taken by the Hubble Space Telescope, but because they know what it looks like, they can mentally fill in the gaps, so to speak.

One more thing…

We hope that none of the above will discourage you from eventually buying, and enjoying a high quality telescope, but until you arrive at that point, we recommend that you get to know the sky with a pair of good quality binoculars. However, binoculars are not created equal, and some are better suited to stargazing than others are, which is why it is important to research the topic thoroughly before you purchase a pair.

Bear in mind that if a particular instrument is significantly cheaper than comparable models, there is a reason why it is cheaper, and that reason usually involves poor optics that are either not coated, or are poorly aligned. Other potential problems involve poorly evacuated (or completely un-evacuated) instruments that can cause the inside surfaces of lenses and prisms to dew up when the temperature inside the instrument changes.

Play it safe, and never buy an optical instrument from a department store. Instead, only deal with vendors that specialize in optical instruments made by reputable and recognized manufacturers. Such a vendor will let you test his wares, answer all your questions honestly, and give you an instrument that suits not only your needs, but your pocket as well.

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