Okay, mister amateur astronomer. That money is burning a hole in your pocket and you can't stop drooling at all those ads in Sky and Telescope or Astronomy magazine. In most cases that money is hard earned and very hard to come by, but your wife (or husband) has allowed you to take a second mortgage on the house or to use your major credit card. Now the question is, what are you going to do with all that money? How are you going to put it to best use? What do you really want to do with that fancy new telescope you are drooling over, and what will you probably end up doing with it?

By far, the most common reason I hear for buying a telescope is that one wants to “do some photography.” I hear that phase so much it seems to be an automatic response. On the other hand, those that actually go that far are few and far between. The second most common reason (a very distant second) is the guy that just wants a light bucket to “see everything I can.” This is a far more practical application and one that is more likely to be achieved. Then there is the “I just want to look at planets and split double stars” guy (or girl). A far rarer breed, they will have no problem reaching their goal if they can afford the scope. So let's look at the different telescopes, their advantages and limitations. Hopefully, this will give you a better idea of how to spend your hard earned money to get the most bang for your buck.

Let’s start with the most common reason to buy a telescope, and that is to do some photography. By far, the best and most practical telescope for astrophotography is the compound telescope, most commonly, the Schmidt-Cassegrain. These telescopes are compact, and designed specifically for that purpose. They are usually equipped with drives and nowadays, GOTO capability. GOTO is a computerized map of everything in the sky and by selecting the object from the database, the scope will automatically “go to” that object. GOTO is a very handy tool if you do not know how to use star charts, or just don't want to look for anything. With the drive systems, you can hook up your camera and the scope will track the objects which is necessary for long exposures. The back of the telescope is specifically designed to hook up a camera so you are on your way. But now we must talk about the reality. You've spent several thousand dollars on the telescope but still need to spring for several more hundred (or thousand) bucks for a good camera.

Astrophotography is a lofty goal, but is it justified so spend all that money and never actually take any photos? Many amateurs end up that way. So instead they attend star parties with their telescope just to observe. Now we must look at the reality. Though Schmidt-Cassegrains are superior for taking photos, as observational instruments, they have a lot to be desired. The long focal lengths, and extra surfaces that the light must go through (or reflect off of), suck the light right out of faint objects. For instance, the most common Schmidt-Cassegrain is the 8”. Now compare the view through one of those with a classic Newtonian (or Dobson) of the same size and notice the difference! The images in the Newtonian are much brighter! The Schmidt Cass can get away with slightly dimmer images where photography is concerned but for observing, the images may be disappointing. The same goes for contrast. A good Newtonian will blow away a Schmidt-Cassegrain with contrast. Another very annoying problem is focuser slop. These telescopes, buy the nature of the focusing system, have an inherent slop in the focuser knob that makes focusing tricky. And though the scope can track, setup time for a Schmidt-Cassegrain can be a real pain.

The second case is the observer, the person that wants to “see everything they can.” Their best choice by far is the classic Newtonian reflector on a Dobsonian mount. In this type of telescope, you get a lot more aperture for your buck. The drawback is that you have no drive system. The Dobson style reflector is designed only for observing because there is to drive system to track the stars. On the other hand, you can set up one of these scopes in just a few minutes while the Schmidt-Cassegrain may take an hour or more to get it to track correctly, depending on how much practice the user has setting it up.

I have heard more than a few times people say they wished they had bought a Dobsonian instead of their Schmidt-Cass, especially after looking through one of comparable size. On the other hand, I have heard people say they wanted to trade in their Dobson on a Schmidt-Cassegrain so they can “finally” take some photos. As a compromise, one can purchase an equatorial mount for their Dobson or even a Dob driver system. The Dob driver system is the same principle as many of the new altazimuth mounted Schmidt-Cassegrains out there. But there is another problem. Newtonians are not designed specifically for photography so the images may not focus when you attach a camera to the scope. This may mean you need to move the mirror cell to bring the image in focus. This minor modification can involve re-drilling holes and maybe even installing a larger diagonal mirror in the tube. Also, an equatorial driven Newtonian reflector is much heavier than a comparably sized Schmidt-Cassegrain. Then you have the balancing problems. One more consideration is that with an equatorial mount, the focuser rotates into some awkward positions so a rotating tube is almost a necessity. And do not think a rotating tube system is cheap! Now back to the simple Dobson mount, you will not have a GOTO system so you will need to use star charts and a finder to locate objects in the sky. Ah, the old fashioned way!

The third use of a telescope is for planetary and double star work. Hands down, the refractor is best for this use. The better ones cost as much or more than a much larger Schmidt-Cassegrain or Newtonian but the images are fantastic on a good night. Another advantage is that they can be used for photography like a Schmidt-Cassegrain. In many cases, amateurs purchase a refractor as a second “specific use” telescope that they only use when they want to split double stars or when the planets are at their best in the sky. On the other hand, refractors are small and almost useless for deep sky observing.

Now how do the Newtonians and Schmidt-Cassegrains do on the planets? On the larger Newtonians, you can cheat the system by placing an aperture mask on the end of the tube. This cuts down the glare and removes the diagonal from the center of the mirror, increasing contrast. The images are refractor-like and on a good night, can rival a refractor. At full aperture, a Schmidt-Cassegrain is a poor performer on the planets, but an aperture mask works on the same principal as a Newtonian the better ones rival an equivalent sized Newtonian when masked. On double stars neither can rival a refractor of the same aperture but usually the size of the optics are so much larger than a refractor that it doesn't matter as much. Depending on your interest, there are only so many planets, and so many observable double stars compared to the amount of deep sky objects out there. Do the math.

So now you have to make a decision. Do you really want to spend a lot of money on a photographic capable Schmidt-Cassegrain when there is only the possibility you may use it for photography someday? Or, do you want more aperture and go for a larger Dobson? And if you are only interested in the planets, are you going to spring for a refractor or buy a larger reflector and cheat the system with an aperture mask? Whichever scope you go for, just make sure you are going to get your moneys' worth out of it!

One more thing before you all think I hate compound telescopes. A compound telescope is usually much lighter than a Newtonian (Dobson or equatorially mounted) and they fold up into a more compact package for transport (most refractors too). For those of you with bad backs and small cars, it would be worth the extra expense for that convenience! My problem is that I am a hard core observer. Despite living in a one bedroom apartment and having a bad back, I still lug around a 16” Dobsonian. The payback is when I look through the eyepiece!