What is a refractor telescope?

In simple terms, a refractor telescope uses a glass lense at its end to gather light, and as it travels through the telescope, the light bends. The light then bounces off a small mirror into the eyepiece, where the viewer sees a larger, sharper image of the object they’re looking at. Another name for this type of scope is a “dioptric telescope.”

 “Refracting” literally means to bend, and the first models of telescope were refractors. Galileo and others who designed the original technology found this method to be the easiest to make. Scopes used on rifles and other guns are refractors, as well as the small telescopes you find at general department stores. This type of scope tends to be tiny, but it’s perfect for looking at the moon and planets within this solar system.

 The benefits of choosing a refractor over, for example, reflector telescopes, start with the placement of the lense. It’s sealed off, so you don’t have to worry about cleaning it often, if ever. Also, images seen through the telescope are sharper and steadier thanks to the tube being immune to changing temperatures and climates.

 There are very few large-scale refractors used for research because of the disadvantages these scopes carry with them. Few and far between, these drawbacks are the reason that most refractors are for commercial use and small observatories. The largest refractor telescope is at Yerkes Observatory, and measures in at 102 cm.

 Chromatic abberation is one of the most common downfalls; light wavelengths bend differently, and because of this, you may see a rainbow effect around the object you’re viewing through the lense. Refracting lenses don’t allow ultraviolet light through them at all, and the thickness of the lense determines the clarity of the other lights that pass through. Also, the glass lense itself will eventually dip thanks to its own weight because it can only be supported by its ends.

 Prices on these scopes vary, but considering the difficulties they present for makers of large scopes, the versions available to the public tend to be within a reasonable price range. For those looking to set up a scope in their backyard for clear nights, roughly $200-400 will get you a great quality starter scope. If you have more to spend, you can look into computerized telescopes, ones with tracking devices, larger lenses, or higher magnification rates. The prices depend on the maker and the technology.

 The beginner lenses generally measure 60mm, 80mm, 90mm, and offer very clear pictures regardless of their small size. Telescopes come with a tripod to set them on, usually with a rotating ball at the center for easy navigation. You can buy a finderscope, which is essentially a miniature telescope that sits on top of the main scope and helps you focus in on the object you’re viewing. It makes observing objects at a distance much easier, and much more accurate. 

 Overall, if you’re looking to view the moon’s surface or planets when they are within range, a refractor telescope is a perfect purchase for you as a beginner.

A Short History Of Refractor Telescopes

Hans Lippershey

A refracting telescope, the first type of telescope, uses lenses to magnify objects. Refractor telescopes are reported to have been invented in the Netherlands, though there is some evidence they had been in use in other areas. In 1608 the opticians Hans Lippershey and Zacharia Jannsen came up with the initial designs. There is evidence of others coming up with the telescope around the same time, Jacob Metius being one who applied for a patent around the same time as Lippershey, and some controversy remains on who the actual original inventor was. Regardless of who credit is given to, the early inventors realized they could magnify objects by looking through two lenses. 

Galileo Galile
Galileo Galilei

Galileo Galilei invented his version of the refracting telescope in Venice in 1609. He presented the telescope to the Doge and was rewarded for his efforts. He made improvements over the first telescopes and was the first to use the telescope for astronomical purposes. He used his telescope to map the moon, discover moons of Jupiter, see sun spots, and Venus’ phases. 

The Galilean telescope design used a concave eyepiece with a convex lens which resulted in the image being right side up. In 1611 the design was changed and further improved by Johannes Kepler. He changed the eyepiece to a convex lens. While this caused the image to be inverted, it made the field of view wider and improved eye relief. The idea of the Keplarian telescope design was first used in a telescope by Christoph Schenier, a Jesuit astronomer, in 1630. 

There were some problems with the early refracting telescopes. They had chromatic and spherical aberration. This caused the telescopes to have a long focal length, some up to 150 feet. This problem was corrected by John Dollond, an optician from Britain, around 1758. He was the first to patent the achromatic refracting lens, though some give credit for this development to Chester Moore Hall. He is said to have come up with the idea in 1733. The achromatic refracting lens was constructed with two different pieces of glass, crown and flint glass. The crown and flint glass had different dispersions which corrected some of the aberrations. Refractor telescope design has changed little since this improvement. The achromatic lenses, however, kept telescopes relatively small because of the limited size of the disks of flint glass. 

A Swiss optician discovered how to make the flint glass larger, allowing for refractor telescopes to be made with a diameter of up to ten inches. The optician was Pierre Louis Guinard. His discovery was not made until late in the seventeen hundreds. Since his time, much advancement has been made in glass manufacturing that has further reduced aberration. Apochromatic refractors are made with extra-low dispersion glass that makes the image sharper and reduces chromatic aberration. 

The largest refracting telescope for scientific research was built by an American optician, Alvan Clark. The telescope is at the Yerkes Observatory of the University of Chicago in Wisconsin. It is a one meter refractor built in 1897. 

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When To Use A Refractor Telescope

Refractor, or dioptric, telescopes are the oldest existing model of telescope. They were used by Galileo and Kepler, among other notable astronomers. Though their design has been improved over the centuries, the general technology has remained the same. Now it is possible for anyone to own a small version of this powerful tool. But, with other choices of telescope available today, how are you to know if the refractor telescope is going to meet your stargazing needs? Let’s find out.

How They Work

Refractor telescopes use a combination of a curved lens and an eyepiece to project an image to you, the viewer. The lens works as an objective, catching a large amount of light and focusing it into a much smaller beam. The beam is directed into the eyepiece, which you can then use to adjust the focus and attain clarity. Often the eyepiece will be set at a 90 degree angle, functioning with the aid of a mirror. This allows the device to be used more comfortably.

Alternatives

The only major alternative to the refractor telescope is the reflector telescope, which uses a series of mirrors instead of a lens to capture light. The reflector telescope was invented to give stargazers another option in the 16th century, at a time when the lenses in refractors tended to have manufacturing flaws. Since production methods have changed since then, the flaws apparent in the refractor model have diminished The choice is really up to you. However, the two models of telescope have different strong points, so there are a few things you will want to consider.

Budget

If you’re looking for a small telescope, the refractor model is slightly cheaper. A good starter size is about 60mm, and that can run you €50-70 (that’s $70-100 American). If you’re looking for something bigger, it is important to understand that lenses get expensive to make as they get larger and mirrors comparatively do not. At larger sizes, a refractor telescope can cost significantly more than a similar reflector, so keep that in mind. If you’re a beginner and you’re keeping it small, stick with the refractor.

Viewable Objects

Sir Paul McCartney croons that Venus and Mars look alright tonight. If you want to see for yourself, the refractor telescope is your best bet. Refractors are more capable of focusing closer objects. The moon, the planets, even the sun (yes there are filters that allow you to view it, though staring at the sun through a magnifying lens is still never advisable) will come in clearer through this model. If you are trying to focus on dimmer, more distant objects like other galaxies and nebulas, then the refractor is not as effective and you might consider the alternative. However, to focus on something so distant you would have to consider a bigger scope anyway.

Conclusion

So, when should you use a refractor telescope? A refractor is recommended if you are a new stargazer. There are no real flaws to set it below the reflector model, and the smaller refractors are cheaper. It is useful for viewing most objects within our own solar system, and is comfortable to look through if it has an angled eyepiece.

Once you have purchased your new telescope, try to set it up outside on a clear night. Looking through a house window will never get you the best results. Also, if it is a particularly warm or cool night, give the instrument 20 minutes to adjust to the temperature before viewing. This will also improve your results. Finally, remember to have fun. The cosmos is an intriguing sight.

Caring For Your Refractor Telescope

Astronomy can be an incredibly exciting and rewarding pastime, and it’s important to learn how to properly maintain equipment to ensure that it remains an enjoyable hobby for years to come. Refractor telescopes have become very popular with less experienced enthusiasts due to their durability and relatively maintenance free operation. The closed optic system does not require any alignment and normally will not need any type of cleaning. However, as with any telescope, refractors still require special care in order to stay in good condition.

Unless the telescope is permanently mounted, it should be kept in a hard case when not in use. If the telescope is mounted in a fixed location, a good soft cover should be used to shield from dust and other contaminants. It is critical that children understand that a refractor telescope, although it looks like a lot of fun, is not a toy and shouldn’t be treated like one. In addition to the damage that could occur to the telescope, injury can be caused if parts or glass lenses become broken. Simply bumping into a refractor telescope can cause it to fall to the floor or tip over and break, so keep this in mind when determining where the best and safest storage place is.

Cleaning the lens and eyepiece is essential to keeping your refractor telescope in pristine shape, but improper techniques can cause permanent damage. Before attempting to clean a lens, it is first necessary to determine what type of cleaning is required. If there is simply dust present, a camel hair brush may be used to gently clear the surface. There is a significant risk of scratching the lens if any dirt or particles larger than dust are brushed. As a result, it is critical that careful consideration is used prior to beginning to clean.

Another product that is actually safer for the glass is canned air, which is available at most office supply stores or hobby shops. The only concern associated with using canned air is that there is an aerosol propellant in the container, and it can actually be expelled if the can is tipped too much. Many individuals believe that they can simply blow the dust off with their mouth, but saliva and small particles can be very difficult to clean if they inadvertently settle on the lens.

If there are any fingerprints or other dirt on the glass, it is important to remove it without rubbing it against the surface. There are many different cleaning solutions available on the market that will allow the owner to simply soak the lens in a container. Many cleaners will dry clear and smudge free, so wiping will not be required. However, the lens can be carefully dried if absolutely necessary. Before drying, ensure that the surface does not have any contaminants present whatsoever. Proper cleaning helps keep the images crystal clear, and much more visible.

One of the great things about refractor telescopes is that of the many objective lenses contained within the unit, only the exposed surfaces require cleaning. Although a novice may hear many other enthusiasts talk about aligning optics, it is important to note that refractors cannot be aligned without sending them back to the factory. The inner lens assemblies should never be disassembled or dismantled, as potentially dangerous gases may have been used in the air sealing process. Refractor telescopes are a very wise purchase for any beginner, but are an equally acceptable option for many more experienced individuals. If properly cared for, a refractor telescope can have an incredibly long life and can be enjoyed well into the future.

Refractor vs Reflector Telescopes

If you are considering the purchase of a telescope, one of the first decisions you will want to make is whether to buy a reflector scope or one that’s a refractor. At first glance, the differences seem pretty clear cut, but the distinctions between the two grow somewhat more subtle the more closely you explore the subject.

Let’s start with the easy part: Refractor telescopes use glass lenses not unlike those found in eyeglasses, while reflector scopes operate with a series of mirrors. So far, so good. It is easy to distinguish between the two different types of telescope at a glance, because they vary significantly in appearance. The refractor scope is long and tubular and probably fits most people’s stereotypical view of what a telescope should look like. Quite different in appearance is the reflector telescope, which is shorter and much larger in diameter than its refractor cousin. While the eyepiece for the refractor telescope is at its back end, the eyepiece for a reflector is generally on the middle or front of the optical instrument.

English astronomist/physicist Isaac Newton developed one of the world’s earliest relector telescopes, a design that remains extremely popular to this day. The Newtonian scope uses two mirrors to focus ambient light into a conical configuration, with the first mirror establishing the cone and the second bending it so that it can be viewed through an eyepiece on the side of the telescope’s barrel-like scope. 

Far older in design is the refractor telescope, which focuses light entering the front or larger end of the tubular scope through a series of glasses lenses to deliver an image through the eyepiece that is located at the back or smaller end of the scope. One of the advantages of the refractor design is the absence of any obstructions within the body of the telescope itself. A telescope of this basic design is essentially the type that Galileo used to make his astronomical observations during Europe’s Scientific Revolution in the late 16th and early 17th centuries.

Both types of telescopes have their champions, and each will argue passionately that the design of their favorite scope is far superior to the alternative. In the end the decision should be based on your own personal preferences and the type of celestial viewing you plan to do. 

If you are going to be searching the nighttime skies for smaller and dimmer objects in space, then you will probably have better luck with a reflector telescope, which because of its broader design admits more light, enabling the telescope user to see smaller objects more readily than might be the case with the refractor. The latter, however, should be more than adequate for those who are content to limit their astronomical searches for larger, brighter objects, such as planets and stars.

If you find you just can’t make your mind up, you might want to consider a compound telescope, which embodies the best of both designs. Alternatively, you may eventually want to purchase both types of telescope. As we’ve already observed, each has its own unique merits, and where the refractor may be a bit weak for some types of celestial observation, the reflector is strong, and vice versa. 

What is a refractor telescope: more

Quite simply, refractor telescopes function by collecting light from the object being observed; therefore, the more genuine light received, the clearer the image. There are a variety of telescopes available, but typically those that have larger apertures achieve better quality. It’s important to understand the way a refractor telescope functions because they are probably the most effective: firstly, a telescope lens will bend or refract the light, and a mirror in the eye-piece will in turn magnify the image, thus enhancing the view. Refractor telescoped were conceived of before reflector telescopes and have a multitude of uses: it’s now possible to understand why many rifle scopes mimic refractor telescopes; it’s because they aid in heightened precision. Another benefit to using refractor telescopes is that they are durable and rarely have misalignment issues like many types of reflector telescopes. 

what is a refractor telescope

Unfortunately, there are some disadvantages to refractor telescopes, and this is why many astronomical research companies rely on them less than before: oftentimes, a rainbow like entity hovers around the observed image, thus making it difficult at times to distinguish the image from the colorful distortion. One way to minimize this effect might be to increase the length of the focal piece, or to use several lenses at the same time in order to balance the distortion, or possibly erase it; the longer the refractor telescope, the more effective it is.

Ultraviolet light cannot be seen in a refractor scope, in addition to other types of light that are unseen because perhaps the scope is not long enough. Some of the original refractor telescopes were used for astronomical research and were built in the late nineteenth century; the refractors contained thick forty-inch lenses and a giant dome to hold the telescope.

Furthermore, a ladder, and an ascending platform were often required to transport the researcher to the eyepiece; the ominously piercing telescope resembled a missile ready for deployment. Although the refractors used to be giant, they are now much smaller and can be used by beginning astronomers and experts alike. Refractors maintain a more crisp and sharper image in comparison to the more common reflector telescopes. Furthermore, most reflector scopes are made cheaply and with less precision. 

For beginners, it makes sense to spot a planet or constellation initially without the use of a telescope. This way the viewer will not be searching aimlessly into the horizon. Moreover, it may behoove of a potential buyer to subscribe to several astronomy magazines, so that he or she can make an informed decision of which telescope to buy. Nowadays, refractors are more common again because of technological advances in components and glass lenses. Again, refractors offer the clearest images because there is little interference in the path of light. 

The study of astronomy has mystified and captivated novices and experts alike for many years. For beginning users, find an area far away from the surging lights of the city, because city light interferes with any potential constellations that could be observed. Therefore, take a trip to a rural setting with thick black skies and little pollution in order to attain optimal viewing. 

Last update on 2020-07-15 / Affiliate links / Images from Amazon Product Advertising API