Add new comment

Telescopes to Help You Touch the Stars

Share

For astronomers, the cold, clear nights of winter present the ideal conditions for stargazing. The dry atmosphere doesn't cause the distortion that humid summer air does. Winter constellations, like Orion and Cassiopeia, are easily identifiable for beginners. Seasonal meteor showers offer awe-inspiring sights. And pre-dawn and dusk skies illuminate dozens of satellites streaking across the horizon. All of these celestial spectacles, and more, await the amateur astronomer and seasoned skywatcher.

Telescopes make good gifts for young people as well as adults. Parents, grandparents, and relatives are often faced with a dilemma, though: they don't want to get a big, powerful telescope, in case it just ends up sitting unused. But on the other hand, they don't want to get a telescope that can't do much, and still won't be used. Like so many such decisions, there is no magic formula. You should consider the person, understand their level of interest and patience, and their ability and desire to learn how to use a telescope. A purist might want a manual telescope and enjoy the setup, alignment, and hunt for the subject as much as the viewing. Someone with less patience or technical knowledge might prefer a Go-To computer-controlled scope that they can set up, align, and find a celestial body with in a matter of a few minutes, and be happy just to sit back and view. You should also know about the different types of telescopes and how they function.

There are also certain terms associated with telescopes that need to be addressed. Aperture, Focal Length, Magnification, and Field of View are important aspects to understand. Additionally, there are several basic types of telescope designs: Refractor, Reflector, and Catadioptric. Finally, there is the mount. The mount is what connects the telescope’s optical tube assembly to, in most cases, a tripod. A basic working knowledge of terminology, design, and mount will be helpful when trying to make your gift purchase

Telescope Terminology

Aperture is the diameter, usually measured in millimeters, of the objective lens or mirror of the telescope. The objective is the largest, main lens or mirror. Essentially, the larger the aperture, the brighter images will appear, and the deeper into space you will be able to see.

Focal Length is the measurement, again in millimeters, from the objective to the eyepiece. This length directly effects the magnification potential of the telescope when paired with an eyepiece.

Magnification is the number of times in size an object appears compared to viewing it with the naked eye. A magnification of 32x means what you are looking at will look thirty-two times larger than when viewed unmagnified. This is calculated by dividing the eyepiece focal length into the telescope focal length. The longer the telescope focal length, and the shorter the eyepiece focal length, the higher the magnification. So, a telescope that has a 1500mm focal length, using a 25mm eyepiece will produce a magnification of 60x.

Changing eyepieces will change the magnification. Most people assume that higher magnifications are better than lower. For astronomical observation, this isn't always the case. At high magnifications, objects can appear dimmer and less clear simply because the light is being diffused too much. From personal experience, a 45x image of Saturn can be much more rewarding (and inspiring) than a larger view of it at 65x that is dim and blurry.

Field of View is just what it implies. It is the area that you can see when looking through the telescope.  A general rule to remember is that the higher the magnification, the smaller the Field of View. Certain specialized, wide-angle eyepieces will be the exception to this rule, but few telescopes will come with wide-angle eyepieces; they are generally add-on purchases for an intermediate to advanced viewer.

Telescope Types

Refractor telescopes are the kind most people think of when they think of a telescope. A refracting scope has a lens at the front—the objective lens; a long optical tube assembly (OTA); and an eyepiece through which you view. With the eyepiece and focuser at the back, users often employ a diagonal mirror to make it slightly more comfortable to view.

Reflector telescopes use mirrors where refractors use lenses to get the light to your eye. A typical configuration has the front of the long OTA open, with a mirror at the back. A smaller, secondary mirror is located about 2/3 of the way toward the front of the OTA. This mirror directs the light into the eyepiece, which is located on the side of the scope. These scopes are often considered to be more comfortable for viewing, since most people can stand up and reach the eyepiece.

Catadioptric telescopes are also called compound telescopes. These use a combination of lenses and mirrors to produce their images, and have focal lengths longer than their optical tubes. The advantage to this type of telescope is that it is able to produce high magnifications with excellent image quality in a compact package, tending to be easier to store and taking up less space for transporting.

The Four Varieties of Tripod Mounts

The most basic mount is the Altitude-Azmuth (Alt-Az), a more advanced type is the Equatorial (EQ). Finally, there are Fork and Single-Arm mounts.

The Alt-Az mount has two axes that run perpendicular to each other. When tracking an object the user makes adjustments to the two axes to keep the subject in the field of view.

The EQ mount is more advanced and requires alignment with the North Star (also referred to as the Pole Star or Polaris). This mount, when aligned correctly, only requires adjustment to one axis to track objects. Using this type of scope requires a certain level of knowledge and patience. You need to do some reading and research to accurately use and align it, but the trade-off in finding and tracking objects is well worth the time and effort.

Fork and Single-Arm mounts are generally reserved for motorized and Go-To scopes. They usually don't have manual adjustments and will come with hand controllers to move the scope.

Alignment

A manual telescope requires the user to make adjustments by hand, either by moving the OTA itself or by manipulating knobs. A motorized scope will have small motors that can move and track objects automatically or with a hand controller. Go-To mounts are computer-controlled telescopes that have the capability to help the user set up and align the telescope, find celestial objects using an internal database, and track those objects while viewing.

With a manual telescope, you have to align the telescope, use star charts or finder scopes to find what you want to look at, and to manually track your subject. You have to remember that the Earth is constantly in motion. This means that as you view an object—whether it's the Moon or a distant galaxy, it will move across your field of view. A motorized scope will track those objects automatically. A computer-controlled telescope can also calculate the relative speed of an object and change the speed accordingly. The Moon, being so close, will move through your field of view faster than a distant nebula.

Telescopes to Consider

For a novice, deep-space objects often take too long to find. The moon and planets are easy to find, and are accessible. Novice astronomers want to see familiar sights from TV and movies. Deep space objects like nebulae or star clusters probably won’t make the same impact that closer objects might. The rings of Saturn or the craters of the Moon are awe-inspiring sights, and easy to see. The Meade StarNavigator refractor offers a lot of technology in an entry-level telescope. It is light and easy to set up, with a motorized mount and computer controller. This controller, the AudioStar, offers Go-To features with virtual guided tours and audio explanations of what your junior astronomer is viewing. Another excellent choice for beginners, also from Meade, is the reflector version of the StarNavigator. This telescope is similar to the one above, but with the larger aperture, you can see further beyond our solar system. These two telescopes offer fast setup, and the Go-To capabilities draw inquisitive eyes skyward and away from their smartphones.

I gave my brother his first telescope when we were both in our thirties. He's an engineer, so I knew that an equatorial mount would fascinate him, and I was right. Learning how it worked, the steps to set it up and find objects—and the excitement that followed when he discovered, for himself, his first deep-space object—made all the hours and days of preparation, before  we ever pointed the telescope into the sky, time well spent and truly a bonding experience for us.

However, as much as he and I enjoyed it, we found it difficult for his daughter to muster the patience to wait and see, and then appreciate, a binary star system. The reason for this was that he and I enjoyed the manual operation of the equatorial mount. For the technical purist in your life, a PowerSeeker from Celestron is ideal. This traditional German equatorial mount requires time before you even go outside to learn how to set it up, align it, and how to find objects. Then you need to research the objects you want to see, and go outside well prepared to do some work before you start seeing anything. While this might not be for everyone, it can be the perfect gift for the right person.

For a more instant-gratification-orientated person with an interest in astronomy, there are a couple of computer-controlled and motorized scopes that will allow for excellent planetary and deep-space object viewing. Celestron's NexStar 6 SE or NexStar 127 SLT offer power in small packages. These two telescopes feature a catadioptric (or compound) style of optical tube assembly. They rely on a combination of lenses and mirrors to produce high-quality images without extremely long optical tubes. The main difference between them is the size of the objective: the larger the objective, the more light can be focused to the eye and the more you can see. They both feature a motorized single-arm Alt-Azimuth mount and the NexStar hand controller. The controller firmware is updateable through a flash-drive port, allowing the telescope to take advantage of improvements over time.

Finally, there is the experienced astronomer. While, on the surface, they might seem like the hardest to buy for, the truth is they are the easiest. There are several ways to approach a gift for them. They most likely have used an equatorial mount and the thrill may have been replaced with a desire to see their favorite objects, or they might just want a smaller, less complicated scope to take on vacation, or to show friends or children their favorites. In this former class, are the Meade LX90-ACF and Celestron NexStar 8 SE. These are large-aperture catadioptric scopes, ideal for deep-space viewing. They offer computer controlled Go-To hand controllers for fast and accurate setup, with a large database of objects into which favorites can be programmed. These advanced scopes are also well-suited for astrophotography and astro-imaging. With the optional accessories and software, they can also be controlled by notebook computers.

If these experienced viewers are looking for a more portable option, the Tele Vue-76 is ideal. Featuring exceptional apochromatic optics, a dual-speed focuser and a wide field of view, this telescope produces clear and bright images with minimal distortion across the whole field of view. The user gets all that and more, with an optical tube assembly that is less than 15" long. This scope is made in the USA and comes with a carrying bag.

Accessories

There is no doubt that telescopes make excellent gifts for people of any age, interest, and experience. Even if the person you’re buying for has their favorite telescope, there are many accessories to expand the use and capability for most telescopes. Eyepieces and filters are always appreciated and are often interchangeable since there are industry-standard sizes like 1.25” or 2”, and the less popular 0.965”. Technological advancements have made astrophotography and astro-imaging accessible to more people than ever before. Camera adapters, CCD eyepiece cameras, software, and computer interfaces make capturing and editing your own photos and movies easier than ever. Finderscopes and alignment tools are also underappreciated and overlooked gift options that even the most experienced observer can enjoy.

Telescopes not only entertain and educate, they also have a unique ability to tap into an almost primal desire to see beyond our world. No one I have known has been left unaffected after a night of telescope viewing. Whether it’s a child viewing the Moon or an adult seeing a distant galaxy, there are infinite wonders to see and a universe to explore. Put the power to look into infinity in their hands.