Revised: February 5, 2005

Purchasing a first telescope is a daunting task.  There are just so many different types of scopes that do so many different types of things.  Apos, Maks, SCTs, achros, dobs, newts...the terminology can get overwhelming!

So instead of trying to explain to you what each type of scope does, I think it's important to outline 5 qualities that should be on your mind when searcing for your first telescope.  In fact, these qualities are relevant to both the beginner and the expert, and serve as general rules to the hobby.  Those qualities, in somewhat descending order of importance, are aperture size, optics, portability, quality, and flexibility.  I'll talk a bit about each of the qualities and what it will mean to you.  Plus, I'll give examples of scope designs that best meet those qualities.

• APERTURE size is important if you like deep sky objects (DSOs) like galaxies and globular clusters, or high resolution views of the planets.  Aperture works in two ways for the observer.  First, it gives a larger opening for collecting light, which is the first job of a telescope in the first place.  Most objects in the night sky are rather large and would be seen by the naked eye if they were bright enough.  Thus, the larger the aperture of the scope, the more likely you will be able to see these objects, even as very low magnifications.  Secondly, aperture serves to provide increased resolution, of detail in your views.  While the quality atmospheric conditions, or "seeing," is the true limiting factor in this regard, most people will find that a good 10" scope will give great details for the majority of sky conditions.  Only occassionally will larger aperture scopes perform at their theoretical resolutions, though make no mistake about it, they will certainly provide some exciting views during moments of excellent seeing!  Of course, those living in good seeing areas, like on the coasts or in the mountains, will be able to make best use of the resolution granted by large aperture scopes.  But the fact that these big scopes will accumulate more light makes them the best, and often only, choice for viewing faint DSOs, regardless of how good your seeing tends to be.
  
  The most common large apertured scope among amateurs is the reflector (aka Newtonian), mostly because it costs the least per inch of aperture when compared to other designs. Most observers of all levels of experience purchase these on a Dobsonian mount - a simple alt-az design - because they give the most bang for the buck, sparing the customer the added cost of a good quality German equatorial mount.   Even so, some people - like astrophotographers - will opt to put such tubes, also called optical tube assemblies (OTAs), on an equatorial mount. But this requires rather large and heavy (i.e. costly) mounts due to the size of the OTAs; hence, the Dobsonian mount has become the most popular choice for general, deep sky observing.   The big negative when considering a Dobsonian mounted reflector is that you are generally limited in the accessories you can include, especially where photography is concerned.   Electronic encoders are an additional expense and tracking platforms, especially the nice dual-axis ones, can add even more to the total
  
  There are several makers of quality Newtonian reflectors in sizes from 3" all the way up to 36"!  Prices vary according to aperture, optics, quality, and features (especially for "truss" designs").   Top notch makers include Obsession, Starmaster, Starsplitter, Teleport, and Mag-One, to name but a few.  Good quality reflectors most commonly purchased are those made by larger companies such as Meade, Celestron, Orion, Hardin Optical, and Discovery, with Discovery bridging the gap somewhat between the budget scopes and those from the aforementioned, top-notch telescope makers.  Those with custom optics will demand the highest prices.  If it comes with optics from the likes of Zambuto, Royce, or Pegasus then you can expect it to be a very nice telescope!  But be prepared to spend money in the thousands of dollars for such quality.
  
  Another alternative when considering a telescope with larger apertures are the Schmidt-Cassegrains (SCTs).   These are excellent choices because they are more compact and portable for any given aperture, and often contain some wonderful electronic features such as automatic GOTO, where you tell the scope where to go and it goes there all by itself.  Thus, gadget "freaks" will certainly enjoy the ability to use their computers to control a large apertured scope.  Of course, these added features come at an increase in price.  Plus, they generally take a long cool-down time and are more susceptible to quality control issues because of the complexity of their electronics and mass-production techniques.  Others will say that the large central obstruction is a negative to the SCT design because of the general loss of contrast; however, my experience has been that contrast seems to fluctuate among samples of these scopes because of a variance in optical quality and poor user collimation from sample to sample. I've seen certain SCTs that exhibit some impressive, nicely contrasted views despite being obstructed.  In my opinion, these design trade-offs are minor negatives for a system that provides such great versatility and power.
  
  Meade produces three SCT models, the LX-200, LX-90, and LX-10 which vary from 8" to 16" in aperture. Likewise, Celestron has available their excellent Nexstar series of fork-mounted scopes as well as their recent, lower priced CPC-series.  Plus, these same tubes, known as the C-8, C-9.25, C-11, and C14 (the numbers are their aperture sizes in inches) are available separately to be mounted on your choice of German equatorial mount, though I'm certain that Celestron would rather you purchase their own CGE mount, which is discounted when purchased with the tube.  Vixen also produces a rather unique SCT variant called the VC200L, which includes that flattening groups in the visual back to go with nice quality optics.  This 8" design lends itself quite well to astrophotography.
  
  Finally, many of the world's best astrophotographers and professional observators will choose the Ritchey-Chretien Cassegrain as their large aperture scope of choice.  These scopes generally combine the best qualities of all the other scope designs.  But this doesn't come cheap!  Expect to pay at least a $1000 per inch of aperture for such scopes.  Likewise, the classical Cassegrain and Dall-Kirkham Cassegrain are choices among large aperture designs.  They are generally longer focal length designs and are still rather expensive.
  
  Regardless, when talking aperture, you will want at least 10" for visual observing of deep sky objects in dark skies.  This is widely consider the point at which galaxy details begin to appear.
  
  Most amateur astronomers will say that aperture size is the most important consideration when deciding on a scope. It's hard to disagree!

• On the other hand, if you determine that observing solar system objects and bright deepsky objects (such as the Messiers) are your favorite, or if you really want to take great astrophotos, then you will want to consider OPTICS, as well as aperture.  Some of the best optical scopes are refractors, Maksutkov Cassegrains (Maks) and the Mak-Newt derivitives, and well-figured and polished newtonians.  Particularly great are those refractors that are described as apochromatic (APO).   These provide exquisite views with very good color correction, a problem with refractors in general.  The only caveat is that APOs come at substantial cost.  For example, a 3" version will cost in the area of $500 to $1500.  This price often doubles for each inch of aperture, and this only includes the OTA (optical tube assembly).  A 4" version might cost $2000 to $2500, the 5" would cost around $3500 to $5000, the 6" would be $7000 or more; you get the idea.  Plus, uou would have to spend an additional ~$500-$3000 (or more) for a mount to go with it since these prices are for OTA-only versions!
  
  Anything larger than 6 or 7 inches in any refractor becomes extremely large, heavy, and expensive, especially if its an APO.   Takahashi, Astrophysics, TMB, Stellarvue, Vixen, TEC, Williams Optics and Televue are the standards here. Likewise, Orion now produces two exceptional nice small APOs, the 80mm ED and 100mm ED, that yield surprising quality at great prices...$500 for the 80mm OTA and $1000 for the 100mm OTA.  These models are highly recommended for the aspiring astrophotographer who is on a budget.
  
  Most of us who own APOs settle for scopes in the 3" or 4" range because of price considerations and portability concerns.  Of course, we eventually yearn for more.  But apochromatic refractors, and to a lessen extent achromatic refractors (achros) , have such high contrast due to their quality optics, lack of central obstruction, high color correction, anti-reflective coatings, and internal bafflings that they tend to show objects in similar detail to that of scopes slightly larger in size.   They even seem to have the ability to cut through nights of poor seeing to give steady views when you wouldn't be able to see anything otherwise, though this is perhaps more of a function of their smaller aperture sizes.  
  
  As mentioned earlier, large Newtonians with great optics will yield uncompromised views.  Newtonians in this category as well as APO refractors will have wide fields of view (in smaller focal ratios) providing the luxury of seeing more of the sky at once.   But many will find that such large reflectors are too cumbersome when compared to the size/performance of an Apochromatic refractor.  Plus, big reflectors are difficult to keep centered on planets unless they are equatorially mounted or sit on a tracking platform.   Thus, for pure planetary performance, I recommend the apochromatic refractor.
  
  The aforementioned Maksukov-Cassegrains (Maks) are also good alternatives when looking for scopes of excellent optical quality; most notably, the legendary 3.5" Questar.   Costing as much, or more, than APO refractors, the Questar is the prime example of how good these scopes can be.  However, lower priced alternatives are the Meade and Celestron series of Maks that are reasonably priced (around $1000 for 5" of aperture). They are often overlooked, but they too have really nice optics.  These scopes even have the luxury of GOTO drives like the big SCTs, though these features are often under-utilized in the smaller aperture sizes...which is the source of lots of criticism among amateurs because you will be paying extra money for a GOTO function that you might not even need.   Afterall, what good is an object-library of 40,000 items if your 3" scope will only show you a few hundred of them from your light polluted site?  Maks have longer focal lengths than normal scopes (due to their design limitations).   This makes them excellent planetary scopes due to the fact that they are more powerful with smaller eyepieces and have very small central obstructions for higher contrast views when compared to other obstructed designs.  The only real negatives to these scopes would be their general quality, especially their enclosures, and the increased likelihood that the scope's electronics gives it more reasons to find its way into the repair shop.  Many people will say that thenarrow fields of view are the only real negatives to these Mak designs, but I'd tend to disagree.  Wide-field eyepieces and focal reducers are available to give you wide enough views, if needed.    And if you are looking for good planetary views, the 7" Maks from Questar and Meade; and the elusive 10" Astro-Physics Mak, are some of the best scopes around, regardless of design.

• The third consideration when looking to buy a scope is PORTABILITY.   This is perhaps the most important factor, especially if you need to travel to dark sky sites or desire quick setup observations (see this article on the importance of dark skies for viewing here).  Scopes bigger than 10" are very difficult to transport (SCTs due to the weight and reflectors due to the size), which is a big reason why many of these scopes never get used.   So, this must be considered in any purchase decision.   For example while being a great performer, a 16" dobsonian (especially the non-truss variety) cannot be carried in anything smaller than a cargo plane (a little exaggeration, but not far off).   Likewise, my 10" LX-200 SCT weighs somewhere around 50 lbs., not including the huge, heavy tripod and wedge (optional).  8 inches in aperture is generally the largest scope among reflectors and SCTs that could genuinely be considered "portable."  Of course, portability in the mind of most advanced astronomers is determined by their passion.  Afterall, portability is often sacrificed for the move to a bigger aperture scope, or scopes.
  
  But unless you are super-motivated, larger scopes are best when you can set them up permanently at home, either in your own observatory or rolled out from the garage.   Of course, this would require reasonably dark skies to begin with, something that a growing majority of people no longer have.   Because of this, it becomes necessary to consider scopes that can be toted easily to darker sky sites.  Some examples are most Maks, smaller Dobsonian reflectors, and smaller refractors on alt-az or light-weight German equatorial mounts.   These can be good first telescopes, especially considering their lower prices.  A person who buys a scope that never gets used will probably leave the hobby prior to finding out how truly wonderful it is.   Lack of portability is a major reason why.
  
  Therefore, quite often the best scope for YOU is the scope you will use most often.

• QUALITY is another important concern. While we've already discussed the necessity of quality optics, the other components such as mounts, focusers, tubes, mirrors/lens, etc., can make or break the your enjoyment of the hobby. Because many scopes are mass-produced, the potential for sub-par quality, or inconsistent quality controls, are always there.   This could come in the form of inadequate optics, breakable plastic parts, and limited or inaccurate electronics, to name just a few.   For this reason, there is a central truth to astronomy, "YOU GET WHAT YOU PAY FOR..."  As with anything else in life, if you put money into it you'll be purchasing a certain amount of quality, and the more you pay, the more quality you get!
  
  Scopes less than $300 can be real pieces of excrement, the exception being some smaller sized reflectors and the aforementioned widefield refractors from a reputable maker.   Some makes like Tasco, Jason and Bushnell, along with the consumer-lines of Meade and Celestrons found at places like Wal-Mart, should be avoided at all costs.   These classes of scopes might be suitable for people with low budgets, especially if their expectations of the scope match their budgets, but generally speaking a good pair of binoculars will likely be the wiser purchase.
  
  Few scopes have perfect track records where quality is concerned.   For example, some of the ETX/Nexstar style of Maks suffer from poor workmanship in the form of mickey mouse, plastic casings, even though the optics remain of good quality.  And even some of the flagship LX200 models will have plastic gears.  User reports help the most when determining which scopes (and mounts) have the best quality.
  
  Quality makes itself most evident in the mount.   Remember this rule: A GOOD SCOPE WITH A BAD MOUNT BECOMES A BAD SCOPE.   Shaky or undersized mounts should be avoided at all costs. As much time should be used in considering the mount as the scope itself, and if you are interested in astrophotography, the mount is by FAR the most important component in the system.  If you are going to buy quality, make sure it comes in the mount!
  

• Finally, you might need to consider FLEXIBILITY when considering your scope.   You'll know more about this trait after you do your homework and you'll likely understand its importance after a year or two in the hobby.   For example, if you decide that you want to do Astrophotography, then you might want a scope that has the versatility of both a good visual and astropix platform.   SCTs are the masters of versatility, designed to be accommodated with tons of options and enhancements that make these scopes extremely powerful in the hands of even the most casual of observers.  
  
  Be careful with some of the extras that come with computerized scopes.  While GPS or global positioning satellite capabilities are more and more becoming standard equipment, they generally provide very little in the way of excess flexibility.  Afterall, if you only use the scope at home, then GPS really only helps on the first night of observing.   Likewise, smaller scopes might be highly portable, but you lose some flexibility because their aperture sizes make them less optimal scopes for DSOs.
  
  Generally speaking, the more money you pay for a scope, the less versatile or flexible it becomes.  This is largely because of  the requirements of specialist activities such as astrophotography, where scopes and mounts are designed with only that in mind.  For this reason, many amateurs will own more than one such scope, each of which with the purpose of doing something different, yet doing it exceptionally well!
  
  But most beginners desire to see a bit of everything, and do a bit of everything, with their first telescopes. Therefore, though the highly recommended 6" or 8" Dobsonian reflector might be a great purchase, some people get a little disappointed when they find out later that the Dobsonian mount is quite a bit lacking for long-exposure astrophotography.  Likewise, those that purchase a small, rich-field refractor will be very disappointed with the views they get on planets.  Rich-field refractors simply aren't designed for anything other than wide-field views of the Milky Way and star clusters from darker skies.  So, my advice is to understand this entirely before making your purchase.

In your search for a scope, be certain to do your homework and if possible seek out a "star party" close to you.  The best way to know what scope is best for you is to actually look through them and ask the owner tons of questions.  You will discover that most all amateur astronomers are more than happy to share their equipment, and talk endlessly about it!

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