Purchasing Your First Telescope

The Warning
Firstly you should take warning from numerous articles about “department trash scopes.” Terence Dickinson is one of Canada’s best known astronomers, astronomy educators and editor of SkyNews. He has written over 35 astronomy books including the best selling, NightWatch, which is still the best primer for someone beginning in astronomy. In a section of NightWatch which deals with astronomical equipment he writes about “Trash Scope Blues” and warns against purchasing the $200 department-store telescope announcing 450-power and several accessories in a box with colorful photos of comets and planets. Our own experience at public events and at trade shows is of many people who have one of these telescopes and who are frustrated at not being able to use it or see anything but the moon. Sadly, many people are turned off from astronomy because they have spent good money for poor results. It becomes difficult to convince them that economical equipment is available that is easy to use and will give them exciting views of hundreds of beautiful celestial objects.
In previous years the glossy photos and promises of high power were bait to catch the unwary shopper. Today the computerized mount on telescopes priced below $500 equally appeals to some the technological instincts of many. Terence Dickinson says, “walk right past the computerized telescope that’s on sale for less than $500 (sometimes much less) in your local big-box discount store. Hundreds of thousands of these scopes are cranked out each year. SkyNews has tested this category of telescope and given models to beginners to try. Our conclusion is that computerized instruments in this price range should be avoided.”  Of course there are exceptions to every rule and now SkyNews (July/August 2008) has given a positive review to the Celestron 130 SLT which is priced at $439.95.

So Many Choices – How do I decide?
When choosing a telescope, the most important question to ask yourself is, “How do I mostly want to use the telescope?” If you have a cabin at the lake or a condo in the mountains or a villa by the sea and you want to primarily use the telescope for daytime viewing, you will choose a telescope quite differently from one that will be used primarily for nighttime viewing. However, the best telescope will be the one that you use the most. If the telescope has poor optics and a wobbly mount like the department store trash scopes, you will not use it long. Nor will you use a really good telescope if it is to heavy and cumbersome to set up.
Let’s begin with the premise that you are looking for a telescope primarily for astronomy. Astronomy is about collecting light from distant objects and the first general principle for astronomy is that you will have a better view if you can collect more light. This means that a larger telescope generally is a better choice than a smaller telescope. This leads us into the discussion of the two major types of telescopes – refractors and reflectors.

A refractor uses glass lenses to “refract” or bend the light and bring it to a focus at the eyepiece. This type of scope is often what we think of as a telescope because we look in one end and point the other end toward the sky or toward the object we want to observe. A refractor generally will give sharp, high contrast views of the moon, planets, double stars and some star clusters.
In contrast, a reflector uses a concave mirror and a second flat mirror to “reflect” the light to a focus at the eyepiece. The advantage of a reflector, also called a Newtonian, is in the ability to build a larger mirror at a lower price than the lens of a refractor. All of the large telescopes in Hawaii, Chile and even the Hubble are reflectors, using mirrors up to 10 meters in diameter to collect light from distant galaxies. For regular consumers, we rarely see a refractor with lenses larger than six inches in diameter. Lenses larger than 6 inches become too costly to manufacture and they introduce distortion that is difficult to overcome.

So which should you buy? If your interest is in viewing the planets and the moon, some double stars, a few nebulas and a few star clusters, a refractor with a 100 mm to 120 mm objective lens may be a good choice. Refractors with smaller lens from 60 mm to 100 mm may also offer excellent views if the telescope has good quality optics, mount and tripod. You should be aware that these scopes of this size are often the ones promising far more than they are capable of delivering.
However, if you are interested in brighter and clearer views of “deep sky” objects such as star clusters, nebulas and galaxies a reflector with at least a five inch mirror likely is your choice. Because the size of the mirror will determine how much light you collect, I always encourage people to purchase the largest reflector that they can handle and afford. Those who purchase telescopes with an eight or ten inch mirror are able to find more and more celestial objects. Their interest in astronomy often grows more quickly than those with smaller telescopes because there seems to always be more and more to find and view. Many people experience “aperture fever” where they continue to purchase or build bigger and bigger telescopes for the bigger and brighter views. A reflector still offers excellent views of the moon and planets although a smaller refractor may offer a sharper, higher contrast view.

Compound Scopes: A third type of telescope is a combination of the refractor and reflector known as a “Schmidt-Cassegrain” or “Maksutov.” Both of these scopes use a similar principle in bending light three times before bringing it to a focus at the eyepiece. These telescopes can be a bit more expensive due to additional manufacturing but they offer a compact telescope with a longer focal length and thus, higher power. For many people the higher power is a disadvantage as objects are more difficult to find and appear to jiggle more readily because of the higher power. But on a stable mount and with a little patience you will enjoy the high magnification views from these scopes. Their advantage is sharpness, compactness, transportability and quick set-up.

Different Views
If you were to look directly through a refractor, the image would be upside down and reversed (mirror image). A 45 or 90 degree diagonal is almost always included with a refractor for ease of viewing and the diagonal also brings the image right side up. Sometimes the view is still a mirrored view with everything right-side-up but reversed. Views through a reflector are almost always inverted. When looking at planets, star clusters and most celestial objects, the observer is not aware that the view is inverted. This makes most reflectors unsuitable for daytime viewing.

Different Mounts
1. Dobsonian mount – Named after John Dobson who developed the initial simple design, this type of mount allows you to manually move a reflector simply and easily in all directions. As the earth spins and stars move across the sky along with the sun and moon, you will regularly nudge the Dobsonian in the direction of the star’s movement. These telescopes have been called “light buckets” because of the large amount of light they can collect at a minimal cost. Terence Dickenson recommends a six inch or eight inch Dobsonian reflector as an ideal beginner’s scope. If you can handle a 10 inch Dobsonian you will have even bigger and brighter views. Many of us began our exciting journey of celestial discoveries with a Dobsonian. Prices have dropped in recent years on most telescopes with an eight inch “Dob” selling in the $400 range rather than in the $700 range only a few years ago. Of note, “Dobsonian” refers to a style of mount that is made available by several manufacturers. As recently as 2007 John Dobson, now 92 years old, was speaking to star parties and assisting with his astronomy group in San Francisco.




2. Equatorial Mount – Both reflectors and refractors come on equatorial mounts. With an equatorial mount you point the polar axis toward Polaris, the North Star. Once you locate the celestial object you will turn a single knob to keep the object centered in the eyepiece in contrast to nudging along the Dobsonian. On some equatorial mounts motors drive the mount rather than having the observer turn a knob. While an equatorial mount may initially seem daunting and difficult, it can be quickly mastered and offers other advantages such as having the telescope up on an adjustable height tripod.


3. Alt-Azimuth Mount - This type of mount may be thought of somewhat like a camera tripod mount where you move it up and down and sideways. This is a mount that offers simplicity of use along with the advantage of having the telescope up on a tripod. You find refractors and compound scopes on this type of mount.

4. GoTo Mount – In recent years computerization has entered the field of astronomical equipment. Many young people come to astronomy through their technical knowledge which is applied to astronomy. A GoTo telescope usually needs some form of alignment with certain stars or planets and then is able to follow those objects and move its motorized mount to hundreds of other designated celestial objects. Celestron and Sky-Watcher are two manufacturers of GoTo scopes that are popularly available.

What Will I See?
We have chosen a fairly arbitrary standard for recommending a telescope. We think you should see Saturn’s rings. Many people have traced the beginning of a wonderful journey in astronomy to their first view of Saturn and its rings. Unless otherwise noted, all of the telescopes we recommend will allow you to see Saturn and its rings, Jupiter and its four moons, the Orion nebula, hundreds of craters on the moon, and numerous star clusters and double stars. All telescopes will allow you to see the oval structure of the Andromeda galaxy. Telescopes with at least a six inch aperture will allow you to see additional galaxies such as the double galaxy M81 & M82.

Our Recommendations:
The best value in an astronomical telescope is the Dobsonian reflector. You will need some simple sky charts such as those available in the monthly astronomy magazines or in NightWatch to know where to point the telescope. I am not aware of anyone who has returned a Dobsonian because it disappointed them. Many, however, quickly trade up to a larger Dobsonian because the simplicity of use, economical price and exceptional views of “deep sky” objects have made them avid observers who want to see more things and to see them more clearly. Again, we recommend the largest scope that you can manage and afford. This scope is easily transported if you have space in your vehicle for it. You will also need a place to store a Dobsonian. While Dobsonians can be purchased in many larger sizes, the most popular sizes are with 6 inch, 8 inch and 10 inch mirrors. A Dob with a 12 inch mirror is also available under $1000 but it is almost more than one person can handle.

Another economical reflector is the 5 or 6 inch telescope on an equatorial mount. The advantage to these telescopes are in gathering a significant amount of light and having the telescope up on a tripod where it can follow a celestial object with turn of a knob. They can be somewhat more readily moved in and out of the house than a Dobsonian. An inexpensive version of this telescope is the 114 mm ( 4 1/2 inch) costing around $200. If funds are seriously limited, this telescope can offer reasonable views of the moon along with some of the planets under good, dark skies. However, we would recommend something larger such as the 5 or 6 inch models.

The Celestron NexStar 130SLT is similar to the above Sky-Watcher but for about $150 more, it includes a full "goto" system.  After an initial set-up and alignment, this telescope operates on the same "SkyAlign" system as its bigger cousins costing thousands of dollars.   While a computerized telescope under $500 was not recommended earlier by the editor of SkyNews,  this telescope has now received a favorable review in the July/August 2008 SkyNews.  The reviewer says, "A generous aperture and ease of use make the NexStar 130SLT an attractive choice for those who want a computerized GoTo instrument that's a step up from the typical beginner's telescope."  - p. 33

Recommended Refractors
 There are a variety of refractors available and it is difficult to narrow our recommendation down to one or two. We tend to favor telescopes with as much aperture as you can handle and afford. The 120 mm Celestron Omni is an excellent refractor. A refractor with a longer focal length will give you the sharpest views. This telescope is mounted on an equatorial mount that is easy to maneuver and track celestial objects. Other refractors with 100 mm objective lenses and smaller may also give you good views if the they have good optics, a solid mount and longer focal length. However, a lot of department store trash scopes fall into this category so you will need to be aware of the quality of the telescope.

A GoTo Scope
If you would like to jump into astronomy with both feet, a compound scope on a fully computerized GoTo mount may be the scope for you. A 58 year old purchased a 9 1/4 inch compound scope (Celestron CPC925) as his first telescope and has been thrilled with the exceptional views. He commented, “this is an amazing instrument…. I could never find and see these objects without this technology. For a person who is so ignorant about the skies and see these objects in a two hour period is absolutely remarkable. I saw things last night I have never seen before. It was a very special and may I say a worshipful time as well.”
A less costly GoTo telescope that still brings in incredible views is the Celestron NexStar SE series. While available in 4 and 5 inch models, we recommend the 6 or 8 inch models. Both the Celestron CPC and NexStar SE telescopes were reviewed in the January/February 2007 SkyNews magazine. Terence Dickinson said, “These scopes are a joy to use….Time after time, it was a pleasure to see each new object emerge right there in the field, with enough magnificaion to see it well. This powerful astronomical instrument is ready to offer a lifetime of observing pleasure…I had similar results with the 6-inch SE….Here are two well-behaved telescopes that get my full five-star recommendation.”

A Great Dual Use Scope
If there was one telescope that we could recommend for the best of daytime and night time observing, it would be the Sky-Watcher 120 mm refractor on an Alt-Azimuth mount. For daytime observing this telescope is simple to set up and use. You can leave it set up on your deck or in font of the living room window and easily pick it up and move it to a new location. It is on an adjustable tripod which allows comfortable viewing. This is a favorite scope for folks who want to watch what is happening on the lake, out on the ocean, on the side of the mountain, out on a prairie field or up in a distant tree. Even with the attached tripod you can carry this telescope short distances if you need a better vantage point. In contrast to the Omni 120 recommended under refractors for astronomy, this 120 mm refractor has a shorter focal length which results in a wider field of view. You can increase the magnification with the second eyepiece for a closer look at your subject.
The telescope also works well for night time observing. Because of its 120 mm aperture you will still draw in enough light to see planets, star clusters and hundreds of craters on the moon. The rings of Saturn are also visible, especially with the higher power eyepiece.
The mount is simple to use, offering both fast and slow motion controls in vertical and horizontal directions.
In comparing this telescope to the 120 Celestron Omni, you will find the Omni to be a better telescope for astronomy but the longer length and equatorial mount make the Omni a bit more challenging to use for daytime viewing.

Photography
Most telescopes can be paired with a camera .   Read our section on "astrophotography" for various possibilities including daytime photography.

Conclusion
Whatever telescope you purchase as your first telescope, we recommend the purchase of the NightWatch. This is still the best introductory book for those beginning in astronomy as it helps you to quickly identify the constellations in the night sky and to find the nebulas, double stars, star clusters and galaxies within each constellation. A second important accessory is a moon filter for comfortable viewing of the moon. When viewing the moon, we are viewing an object standing in broad daylight and the telescope collects hundreds of times the light that your eye collects. So without a moon filter it is similar to someone shining a flashlight into one eye. A moon filter, also called a neutral density filter, will simply cut the amount of light from the moon and allow you to continue observing other objects also. A third recommended item is a red LED flashlight. It can take up to 20 minutes for your eyes to adapt fully to the dark. Once your eyes are fully adapted to the darkness, you will be able to see everything, including the fainter nebulas and galaxies better than if your eyes are not dark adapted. A red LED flashlight allows you to change eyepieces and read sky charts without losing your night vision. These three items are sold as a package or individually.
Finally, let us encourage you to take the plunge. You will have a lifetime of observing enjoyment if you purchase a telescope knowing its capabilities. When compared to a lot of recreational products, astronomy is affordable and enriches your life in ways not otherwise possible.

May all your skies be clear!