SJAC Astronomy and Telescope Primer

I’m putting this article together to provide those interested in Astronomy with some advice and direction when starting out. I’m working under the assumption that most people reading this have access to the Internet and are willing to pursue further research beyond the scope of this article. With Ed Ting’s permission I am starting with his Advice for Beginners, followed by some tips and Etiquette suggestions from the Rose City Astronomers Club, some suggested readings, a list of Internet Links, and Member Contacts for individual questions.

So You Wanna Buy a Telescope… Advice for Beginners
By Ed Ting

So, you’ve decided to take the plunge and buy a telescope — congratulations! Astronomy can be a life long pleasure, with the right equipment. But what to buy? There’s more equipment out there than ever before. This article will attempt to make some sense out of the seemingly huge selection of scopes and accessories.

Ready? Good. Let’s begin. First of all, some words of advice:

1.   Learn to spot a few constellations and maybe a planet or two with the naked eye. If you can’t point to M42, how do you expect to able to point a telescope (which has a much narrower field of view) there?

2.   Subscribe to one of the two major magazines, Sky and Telescope or Astronomy. These will get you started not only with finding celestial objects; it will also acquaint you with the variety of equipment out there. Don’t buy anything yet!

3.   Join a club, or tag along on one of their observing sessions. This is the single best piece of advice I can give you. There is no substitute for spending time with real equipment out in the field. You may discover, for example, that you like the portability of Schmidt-Cassegrains, or that you enjoy the views through a good refractor, or that the big Dobsonian you saw in the catalog is much more of a handful than you imagined. Or whatever. There’s no substitute for experience.

That said, your ideal first telescope might not be a telescope at all, but a pair of binoculars. Perhaps you have a pair lying around the house already. Most experienced astronomers keep a pair of binoculars close by, for quick peeks or for scanning the field of view before using their telescopes. The common recommendation is to get a pair of 7X50’s, or at least, 7X35’s. The first number “7” is the magnification, the second “50” is the aperture of each objective lens, in mm. You want the largest lenses you can comfortably hold.

Many astronomers opt for 10X50’s, although you should make sure in advance that you can hold them steady at that power. It seems that the current trend is towards 10X50’s, but I still like the traditional 7X50 size.

Finally, there are new “giant” binoculars, which can give stunning views of the heavens, if you know how to use them. If someone offers you a view through one of these, by all means oblige, but hold off buying a pair for now. You’ll know later if you want them.

OK, so binoculars aren’t exciting the way telescopes are. Before I leave the topic, allow me to make a final case for good binos:

1. Cheap binoculars are much, much more useful than cheap telescopes. Trust me on this one.

2.   Good binoculars can last you a lifetime. As you trade up (or down) your telescopes, you’ll still need a pair of binos for quick peeks and scanning. As a result, binoculars tend to be something you buy only once or twice.


Ask a roomful of people what the purpose of a telescope is, and chances are they will say something like, “to make distant objects look bigger.” I’m a frequent guest speaker at local schools, and I always get that answer (or something close to it) when I ask that question.

 Is the primary function of a telescope really to make things look bigger? Take this test. Step outside on a clear night from a brightly lit room. See anything? Probably not. But it gets better after a few minutes, doesn’t it? In fact, after a while, you’ll wonder why you didn’t see all those stars before. What made it better? Did you change the magnification, or make the apparent size of anything change? Of course not. What you DID change, was the amount of light your eye gathered, when your pupils opened to compensate for the darkness.

So, the primary function of a telescope is to gather light.

The more light a scope gathers, the more powerful it is. And remember, telescope apertures are circles, and the areas of circles increase with the square of the radius, so moving up in aperture, even modestly, can yield big results. Our hypothetical 7X50 binoculars (above) gather over twice the light of the 7X35’s, even though they look about the same size. Put another way, the owner of a 10″ Schmidt-Cassegrain who decides to upgrade to a 12″ will see a 44% increase in light-gathering ability. Not bad for a 2″ increase, eh?

So, you should buy the biggest telescope you can afford, right? The answer is an unqualified MAYBE, and for some people, the answer will be NO. But we’re getting ahead of ourselves.

Types of Telescopes

Modern amateur telescopes can be divided into three classes:

The refractor is what most people think of when they hear the word “telescope”. Refractors gather light with an objective lens at one end and focus the light at the eyepiece at the other end. Refractors were almost extinct at one point, but modern glass elements (including an exciting new artificially grown crystal known as fluorite) have brought the refractor back to prominence.
Refractor advantages: Potential for the best images, no obstruction in light path.

Refractor disadvantages: Some secondary color (“chromatic aberration”) still visible in all but the best units, large aperture instruments can be massive, most expensive of the three designs (often by a large margin), “Guilt By Association” with horrible department store refractors.

The Newtonian Reflector, invented by Sir Issac Newton, uses a parabolic mirror at the end of a tube and focuses the light back at the front of the tube, where the eyepiece sits, after being deflected by a smaller secondary mirror in the light path.

Reflector advantages: Cheapest of the three designs (especially those on Dobsonian mounts), more portable than refractors of similar aperture, inherently color free (no chromatic aberration).
Reflector disadvantages: Secondary obstruction results in some loss of contrast, still quite large compared with Schmidt-Cassegrains, can require frequent collimation (alignment) of optics.
The Schmidt-Cassegrain and its derivatives (Maksutov-Cassegrain, Classical Cassegrain, etc.) use BOTH mirrors and lenses to fold the optical path back onto itself, resulting in a compact tube. The technical term for these scopes is catadioptrics, but since nobody seems to use this term, I won’t.
S-C Advantages: Most compact of the three designs, less expensive than refractors, huge assortment of after-market accessories, can be totally computer driven, very popular.
S-C disadvantages: More expensive than reflectors, images are potentially the worst of the three designs (notice I said “potentially!”), most subject to dew of the three designs.

So, which one should I buy?

Depends. The “right” telescope depends on you, your observing habits, and your financial situation. Picking a telescope used to be a simple matter. You started out with a 60 mm refractor (probably from a department store), then you upgraded to a 6″ f/8 reflector from either Criterion or Meade, and if you stuck with it long enough, you eventually bought an 8″ Schmidt-Cassegrain from Celestron.”
My, how things have changed. Throughout the 1960 and 1970’s, the Newtonian reflector ruled the amateur roost. From about the 1980’s onward, astronomers flocked to the portability of Schmidt-Cassegrains as both Meade and Celestron duked it out to try and out-do one another on features. Then, the refractor, long given up for dead, came roaring back with the advent of ED and fluorite glass. Now, you see all three designs in use regularly.
The advantages/disadvantages of each design are well-documented elsewhere, so I’ll attempt to give you some “other” information which may be useful to you.
Despite the optical superiority of good refractors and the lower cost of reflectors, most astronomers still wind up with Schmidt-Cassegrains as their primary instruments. It’s not hard to see why. A 10″ S-C is relatively affordable and portable. A 10″ reflector is a handful, especially an equatorially-mounted one. And a 10″ refractor? Forget it — you’ll probably need a separate observatory to house one.
4.5″ or 6″ reflectors make excellent beginner’s instruments. For $300-$650, you get a decent aperture and a scope that’s relatively portable. On the refractor side of the table, look for an 80 mm scope on a stable mount.
Avoid like the plague any cheap refractor sold on the basis of its magnification. A “675X” 60 mm telescope is almost certainly a piece of junk. Maximum useful magnification is usually given as 50X-60X per inch of aperture. Thus, the 60 mm example given above is really only a 120X-144X telescope (and its images will probably break down well before that point). You find these scopes all over the place, in department stores, toy stores, “Science & Nature” centers at the mall, etc. This is not just what Ed Ting thinks you should do. This same important advice can be found in any responsible text on telescopes.
I’ll say one thing for Newtonians. They’re the most comfortable to use of the three designs. The eyepiece is nearly always at a convenient height. Refractors are the worst in this regard. Looking at anything near the zenith with most any refractor is a less-than-appealing proposition.
Many astronomers give up trying to decide what’s best for them and buy more than one scope. While this may not be the best advice for beginners, newcomers might want to keep this in mind when making a purchasing decision. For example, if your first scope is an 80 mm refractor, you might balance things out by getting a 12″ Dobsonian in a year or two. That way, you’d have both a light bucket and a planetary/double star scope.
Avoid any thoughts of astrophotography for now. You are going to have your hands full dealing with the scope itself. Trust me. More astronomers leave the hobby due to excessive involvement with astrophotography than for any other reason, save the cheap department store telescopes.
Finally, avoid “paralysis-by-analysis.” If you spend more than an hour a day reading telescope catalogs, you are probably in this category. Just get something; you’ll feel a lot better.

Which one would you buy, if you could only get one?

This is a tough one to answer, since everyone has their own priorities and preferences. Still, knowing what I know, if I were starting out today, I would probably get a 6″ or 8″ Dobsonian-mounted reflector. The fact that I am something of a “refractor guy” says a lot about this choice.
A 6″ Dobsonian is simple, cheap, and will teach you a lot. The simplicity part is important; since you will spend your time aiming and observing with your telescope, rather than playing around with the sometimes-complicated controls on an equatorial mount. Beginners need early success, and the 6″ or 8″ aperture is big enough to throw up a bright image of most common celestial objects.
I like all the 6″ Dobsonians from Meade, Celestron, Orion, and Discovery. I like the Orion the best, but you can just pick one; they’re all good. If you’re feeling ambitious, get an 8″ version. The differences between the brands show up mainly in the quality of the accessories. Look for a 6X30 finder (or larger), Plossl instead of Kellner eyepieces, and Pyrex instead of plate glass mirrors. If I were pressed to recommend one telescope for beginners, it would be the Orion Skyquest XT8.


Here’s one area where beginners tend to go overboard. You don’t really NEED more than 3 or 4 carefully chosen eyepieces, a barlow, and perhaps a filter or two, but most of us eventually wind up with collections, some of them needlessly impressive. Still, the first accessory a newcomer buys is usually a new eyepiece. Below is a guide to various designs.

1. Ramsden and Huygenian – These are 2-element eyepiece designs. While simple, they exhibit narrow fields of view; have numerous aberrations, and terrible edge correction. Generally supplied only with the least expensive telescopes. While not of much use visually, they make good solar projection eyepieces (i.e. you can risk ’em). About $25-$40.
2.   Kellner – A three-element design that shows an acceptable 40-45 degree FOV, and good correction of spherical and chromatic aberration. Offshoots include the Meade MA, Celestron SMA, and Edumnd RKE. A decent general-purpose eyepiece for the price. About $30-$50.
3.   Orthoscopic – These eyepieces were once considered the best for general use, but have lost some of their luster compared with newer Plossl designs. Using 4 elements, they are still popular for planetary work. They are well corrected throughout their 45 degree FOV. About $40-100.
4.   Plossl – Probably the most popular eyepiece design today. Using 4 or 5 elements, they are very well-corrected and have a wider (50-52 degree) FOV than Orthoscopics. However, some models have shorter eye relief than equivalent Orthos. About $50-$150.
5.   Erfles – Using 6 elements, Erfles throw up a wide 60-65 degree FOV, with increasing distortions near the edge. Rapidly becoming extinct. About $75-$150.
6.   Many observers find a barlow lens to be a valuable accessory. Inserted between the focuser and your eyepiece, a barlow will typically double or triple the magnification of any eyepiece. Thus, for $60-$100, you have effectively doubled the number of eyepieces. Also, a barlow preserves the eye relief of your longer focal length eyepieces, thus reducing the amount of squinting you have to do.

What can I expect to see?

Next to “What telescope should I buy?” this is the most common question I usually get asked. This is a tougher question to answer than you may think. What you can see depends on a lot of factors, including the type of telescope you bought, the quality of your local seeing conditions, and your level of skill.
Since the quality of your instrument and conditions are largely out of your control, it would make sense to hone you’re observing skills. Sadly, I don’t see this happening much anymore. Observers, eager for instant results, often upgrade to larger and larger telescopes without bothering to learn how to “see” properly.
Seeing well is both an art and a skill. You need to spend lots of quality time with your telescope. The more you look, the more you will see, and the better you will get. As a result, an experienced observer might enjoy deep sky objects in an 80 mm refractor, while a beginner with a light bucket next door is still struggling to find the Orion Nebula.
Astronomy is a patient hobby. Don’t be in too great a rush. The cosmos will still be there tomorrow. 
OK, now that the lecture is over, here’s what you can see with a typical 6″ reflector under reasonably good skies:
1.   All 110 Messier objects, which includes nebulae, open and globular clusters, and extended galaxies. Most of these will seem impossibly dim to you at first. Later in your career, they will seem really bright.

2.   All of the planets except Pluto. Saturn’s rings are easy. Shadow transits on Jupiter are easy. Detail on Mars is somewhat harder, but gets a little easier once every two years. Venus, Mercury, Neptune, and Uranus are pretty much featureless balls.

3.   Hundreds of named craters on the moon.

4.   Sunspots and other activity on the sun, with a proper filter. Do not look at the sun without proper filtration!

5.   Hundreds of other various objects.
In summary, here are the prominent points given above: 

1.   Binoculars, even cheap ones, are sometimes a good substitute for a cheap telescope. In addition, binoculars are almost always good companions to a telescope.

2.   Avoid department store, toy store, and “Nature/Science” store telescopes. I cannot restate this strongly enough: STAY AWAY from department store telescopes!

3.   The primary purpose of a telescope is to gather light. Thus, all other things being equal, beginners should buy the largest aperture telescope they can afford. A 6″ Dobsonian reflector is an excellent first telescope.

4.   BUT, if the instrument is too large, you may never use it. Be realistic about what you’re willing to lug around.

5.   You don’t need more than 3 or 4 carefully chosen eyepieces in your collection at first. The minimum quality you should consider are Kellners (and their offshoots). A barlow is useful tool for doubling your collection at minimal cost.

Stargazing Tips

The Rose City Astronomers Club has provided the following stargazing and etiquette tips.
1.   NEVER look directly at the sun with the naked eye, binoculars, or telescope. Permanent blindness can result! Special filters are available from astronomy sources and are required for solar viewing.
2.   Prepare for an evening viewing session by becoming familiar with star charts of the current night sky. Develop a small list of specific objects to identify. Bring your binoculars. It’s amazing how much you can see with them if you know where to look.

3.   Abstain from any smoking or alcoholic beverages. These substances poison optic nerve transmissions and decrease night vision considerably. Anyway, alcohol is not permitted in State Parks, such as Belleplain.

4.   Be well rested. Fatigue decreases accuracy and enjoyment and may ruin an otherwise good evening.
5.   Bring more than what seems to be enough warm clothing. Since you are sitting quietly for extended periods, your body doesn’t manufacture much heat. Even summer evenings can get pretty cold. A hat or some type of head covering is essential. Gloves, warm socks, warm shoes, insulated underwear, and warm outerwear are standard. Ski clothing is a good option. Layer clothes to allow for adjustment of temperatures.
6.   Eat something with sugar 30 minutes before observing. This will increase your energy, attention, and warmth level. Hot chocolate or soda pop are also good choices. Artificial sweeteners are not helpful.

7.   Bring your kids. Many kids get cold and tired early, so bring a sleeping bag for them.

8.   Bring a folding chair of chaise lounge. It’s nice to sit under the stars, listening the quiet sound of voices in the night.

9.   Plan to remain in the dark for at least 30 minutes prior to observing really dim objects. It takes a healthy retina 45 minutes to adapt to the dark. Be sure your glasses and/or contact lenses are clean.
10.  Use a dim, red-lens flashlight to check charts or books. The night portion of the retina is least affected by red light. To make a simple viewing light, you can cover any flashlight with red construction paper or thick cellophane. In addition, it is a courtesy to any other observers that are in the vicinity who will appreciate their night vision not being ruined by your light as well.
11.  An ideal observing spot is high with 360 degrees of view. A small clearing surrounded by trees is even better because it provides a wind break that will help prevent cold fingers, flying book pages, and shaking equipment. Try to pick a spot removed from streetlights and traffic. It is a good idea to check out your observing site in the daylight before your viewing session.
12.  Check the moon phase. Even a bright quarter moon can make faint objects difficult to see. But then, looking at the moon can be a pretty interesting experience itself!

Star Party Etiquette

Most amateur observers enjoy sharing their telescopes with anyone who happens along. They are sensitive creatures, though, and react strongly to the presence of even small amounts of white light. So:
1.   Park away from the viewing field if you arrive after dark or expect to leave before dawn. Remember, your vehicle back-up lights are bright white. A good idea is to back your vehicle in at the start of the evening so that when you leave, you can pull straight out rather than having to back up. If you’re not bringing a telescope, it is best to park in the lot and walk out onto the ballfield, that way one can leave at any time without inconveniencing the other astronomers.

2.   If you have to drive out onto the field after dusk, please turn off your headlights, usually an SJAC member will walk out to safely guide your car to a suitable spot. If I am late, I turn off my headlights right after the gate and give my eyes a few minutes to adjust as I cover up my license plate lights with a towel and close the gate behind me. By this point I can see well enough to drive up the dirt road to the field entrance with my parking lights. After I pull onto the field, I stop and walk over to ask somebody to guide me to a spot.

3.   If you park on the viewing field, either disconnect the overhead light in your vehicle or cover it with red tape. This protects other viewers from flashes of bright white light when car doors are opened during the evening.

4.   Each person should have a red flashlight for use at the site. It is easy to modify a regular flashlight by covering the lens with a red filter. Red construction paper, red fabric, red cellophane (thick layers), or red taillight repair tape works great to make filters.

5.   If you set up a telescope, be sure to put it several yards away from your closest neighbor. Many people need room for star chart tables, chairs, power supplies, cables… and especially for long lines at the eyepiece.

6.   Some people have expensive equipment at star parties. Most astronomers are eager and enthusiastic to share the view from their instruments with everyone. Don’t be afraid to ask the owner for a view through their telescope. However, before you try to move or adjust someone else’s equipment, ask if it is OK and how to properly do it. They may want to do it for you.

7.   Astrophotography/CCD imaging is an increasingly popular hobby of club members, and many will set up their equipment at star parties. If you are planning on taking pictures, let those around you know that you have a camera set up so they can be careful about their red lights. On the other hand, be sure to check around you before flashing your red lights, opening car doors, or using any running lights on your car when leaving so you don’t inadvertently ruin someone’s once-in-a-lifetime 45-minute exposure at the 42-minute mark!

Books and Atlas

Planisphere – The first thing to do is to find the main constellations. A planisphere is a rotating map which by dialing in your local date and time and it shows you the locations of the constellations and deep-sky objects as they appear in the night sky. You rotate the top piece of plastic to match up the time and date. Then hold it up and you should be able to match the diagrams on the chart to the sky. This is easiest in a fairly dark sky, so you can find the bright stars. A *very* dark sky makes this harder since you will see so many more stars.
Nightwatch by Terence Dickinson – Considered to be one of the best books on amateur astronomy ever published. It covers everything from how to observe to how to buy a telescope. 
The Deep Sky, An Introduction by Philip S. Harrington, Leif J. Robinson – It covers about 300 of the best sights for amateur astronomer including: multiple and variable stars, asterisms and all types of deep sky objects. Just about everything that really looks good in amateur instruments from binos to medium size telescopes is in here. This book also has an excellent set of star charts and data tables

Turn Left At Orion by Guy Consolmagno, et al: Teamed with Nightwatch, this is a superb starter set for the new amateur astronomer. Turn Left explains how to observe the 100 finest sights in the nighttime sky. It includes easy to use, detailed finder charts and a clever rating system to get you started looking beyond the obvious and into the mysterious. This is the first astronomy book I purchased and I highly recommend it along with a planisphere to get started observing.
40 Nights to Knowing the Sky: A Night-By-Night Skywatching Primer by Fred Schaaf – A practical, interactive guide for learning astronomy. The program is a system of practical objectives and activities that get readers actively involved in skywatching. Starting with simple instructions on learning one’s way around the night sky and progressing to more challenging concepts, each night’s activity takes the reader to a deeper level of knowledge and understanding.
This is not a definitive list, merely a starting point. A good source for these and other Astronomy-related books would be

My Personal Experience

When I decided to get into astronomy, I had every intention of purchasing a 60 mm refractor (the most popular size for “department store scopes”). I was able to contact Fred Schaaf through his “South Jersey Skies” column in the Atlantic City Press. His advice was to save up for a 6” reflector. I decided to wait and save up for a larger scope. I purchased a planisphere and a copy of “Turn Left at Orion”. I dug up an old pair of binoculars and proceeded to learn about the sky.
For about a year, I attended meetings and the occasional Club Skywatch. I found the club members more than happy to let me look through their telescopes. When I was ready to purchase I was torn between an 80 mm Short Tube refractor (portability) or a 4.5” to 6” Dobsonian reflector. At the first SJAC Star Party I had the opportunity to look through an 80 mm (~3”) refractor and an 8” Dobsonian side by side. There was no comparison; at that point I knew I was going to get a reflector. I had found a small company in Canada (Stargazer Steve, aka Steve Dodson) that made telescope kits. I had contacted the owner earlier about a 4.25” Dobsonian kit that was reasonably priced, he informed me that he was coming out with a 6” reflector in a few months, so I got on the waiting list.
Why a kit, you may ask? At the time, the Dobsonians from the big three (Orion, Meade, and Celestron) consisted of a particleboard base and a painted cardboard tube (sonotube). Years ago, I had the pleasure of lugging a particleboard computer desk up two flights of steps to my apartment, since then I’ve had a deep and abiding hatred of anything particleboard. A 6” Dobsonian reflector from the big three weighs 35 to 45 lbs. My Stargazer Steve 6” Dobsonian weighs 24 lbs. Instead of particle wood, the base is birch plywood. The tube of the scope is sonotube, rather than painting it, I covered it with Coverite, a cloth-like material that can be attached and shrunk with a hot iron. I took the time to assemble, sand, and stain the base. I’ve been very pleased with the scope, it has held up very well. As for customer service, it’s not often one speaks with the owner of a company. Of course a kit is not for everyone but it worked for me.
Last year, I had the opportunity to pick up a used Orion XT8 (8” F6) at a reasonable price. This is a Dobsonian reflector with steel tube and particleboard base that has gotten good reviews. The tube and base weigh about 58 lbs, so it is a bit of a handful. On the up side, it is a very stable scope. Once the scope is collimated, it rarely needs adjustment. For a beginner, this is a big plus. In the future, I will probably replace the base with a wood one and cover up the tube.
Most Dobsonians come with a finderscope, usually 6×30 (6x magnification, 30 mm aperture). These are okay for finding planets and brighter stars. My preference is for a unit finder (1x magnification). A unit finder (Rigel Quickfinder or Telrad) projects a red LED bullseye against the sky. Since you can see the entire sky it is easy to point the scope to an area of interest and then locate the desired object with a low power eyepiece. My Stargazer Steve came with a Rigel Quickfinder instead of a finderscope. The XT8 has a good quality 6×30 finderscope, but after trying both I still prefer the Quickfinder. On the other hand, I could get a bigger finderscope for the 8”, but that will have to wait.

Internet Links for more information your have access to the web, here a couple of good sites (out of many). All of these sites have additional link listings for further research.
1. Sky and Telescope Magazine:  – On the left side of the screen select “How to” and check out the “Astronomy Basics”, “Visual Observing”, and “Telescopes and Binoculars” selections to learn some of the basics. The “Observing” section is also worth a look. The old Sky and Telescope site had an archive of Telescope and Binocular reviews, the new site now keeps an archive of available.
2. Orion Telescopes and Binoculars: – Besides having lots of telescopes and accessories for sale, there is a lot of info for beginners. Select “Learning Center” for a list of articles. Not the least expensive, but customer service is impeccable. The XT line of scopes (4.5″, 6″, 8″, and 10″ Dobsonians) are a good choice for beginners. See the website for reviews of these scopes. Request a free catalog via the web site or by calling 1-800-447-1001.
3. Martz Astronomical Association & Martz Observatory: – Under “Eductation > Observatory Lecture Series” there’s some good beginner advice, equipment and book reviews.
4. Cloudy Nights Telescope Reviews: – From the web page – “Reviews of astronomical scopes and equipment as written by experienced observers in the amateur astronomy community. Our goal is to assist amateur astronomers in their purchasing decisions by presenting comprehensive and in depth reviews of astronomical equipment and accessories.”
5. The Telescope Review Site: – Ed Ting’s website with over 100 telescope reviews plus beginner’ advice. The Beginners’ Advice section is well worth reading and provide the basis for this overview.
6. Rose City Astronomer’s Club: – The Frequently Asked Question section provided the basis for the Stargazing Tips and Etiquette portion of this document. The entire section is worth reading.

What to Bring

1. Red Flashlight
2. Telescopes and eyepieces, binoculars or a pair of eyes
3. Planisphere and/or Atlas
4. Extra warm clothes
5. Don’t be afraid to ask questions (We won’t bite, unless you drive onto the field with your headlights on).