Buying A Telescope

Buying a Telescope: What kind of telescope should I buy? Advice and a simple guide for those buying their first telescope.

I get asked this question as soon as people find out that I'm into astronomy and telescopes. It is fun for me to help folks to answer this. Often I find that what kind of telescope people think they want and what they really want are two very different things. So, to start, I ask people two questions that need to be looked at together... •

What do you really want to do with a telescope?

•

How much money do you have to spend?

Many times after asking these questions I find out that what someone really wants is a fancy living room decoration and not so much a good star gazing instrument. How can you tell? Well if someone says they want to spend less then $250, I will usually come back with two answers 1) Get a good pair of binoculars. 2) Get a Dobsonian. What happens to tip me off is that their nose sort of scrunches up at these suggestions and they go out and buy a cheap Newtonian or Refractor with the cool looking (but cheap) mount and flimsy tripod. It looks good in the living room window but is so frustrating to use that it stays there. Instead of taking some time and looking seriously, they run off to the local mall or XYZ-mart and buy the $149 650x special. So if you are looking into buying a telescope here is some advice for you...

Choosing & Buying a Telescope: The Basics However, for those that have at least a mild interest in astronomy, who actually want to look up and "see the stars" and are not looking for a fancy living room decoration here are some basic rules of thumb... •

START WITH BINOCULARS

If you do not have much money (say not more then $250) you may be happiest with a good pair of binoculars. Binoculars, even inexpensive ones, will amaze you with how much you can see of the night sky. I viewed the sky far more often with my cheap ($98) 10x50 binoculars then my 10" telescope. •

DO NOT BUY A TELESCOPE BASED ON POWER!!!

If a telescope has "650x" (or any other reference to power) prominently displayed on the side of the box, walk away - No RUN AWAY. Even the best telescopes are limited to about 50x-75x per inch (25.4mm) of aperture. For an inexpensive 60mm refractor this equals 120x. So "650x" is just a marketing ploy to get you buy their inexpensive scope. Although this practice is not as common as it once was, still... Do not buy a telescope based on its power! Do not buy a telescope based on its power!! Do not buy a telescope based on its power!!! •

APERTURE IS KING

The diameter of the lens or mirror is generally the most important attribute (but not the only one) to consider in a telescope. Generally one will be happiest if they buy as much aperture as can be had in their price range. Large aperture refractors (lens based) can bevery expensive. That means that most of us will be looking at a mirror based telescope.

•

SOLID MOUNT

One can have the best optics in the world, but if the mount is wobbly, shaky, hard to use, or hard to track the sky with, you will NOT be happy. A good combination of aperture and solid, easy to use mount is a Dobsonian. Those department store telescopes almost always have poor mounts. •

USED TELESCOPES

Often, if you do not need to have the latest gee-wiz scope (and sometimes if you do), you can save a lot of money by buying a used telescope (This is what I did). Older model telescopes are often available on the used market for less then half of the cost of a new telescope. Serious used telescopes are almost always in excellent condition as the owners take very good care of them. See the links at the end of the page for online used telescope classified ads that I have used in the past. •

KNOW WHAT TO EXPECT

The views through your telescope simply will NOT match what you see in astrophotos in magazines or even on the box of your scope. Period! First, you will not see nebulae in color, planets will look tinier then you expect and will lack most of the color and contrast you see in books and magazines. Most people that look through a telescope for the first time are somewhat disappointed about what they see, or what they don't see. Don't get me wrong, you will never forget the first time you see Saturn or the Moon in a telescope and the "Wow!" that escapes your lips will amaze you also, but the "faint fuzzy" stuff often disappoints first time viewers.

What Telescope is Best for Me?

Answer: A telescope that you will continue to use and enjoy, NOT a device that will frustrate you to the point of never wanting to use it again. Really though, the answer depends on what your goals are and the money that you have to spend. Good telescopes are expensive regardless of the type. Now, I am going to assume that you know the difference between a refractor and a reflector and their variants. If not, click here and a new window will open that shows the difference. One word of caution, A good telescope will likely cost more then you want. The first thing you must do is answer this question: WHAT DO I WANT TO DO WITH MY TELESCOPE? •

I DON'T KNOW WHAT I WANT.

This is simple, get a good pair of binoculars and a star chart. You will be amazed at just how much there is to see through a good pair of binoculars. Generally a 7x50 or 10x50 is a good start, a 8 x 56 or a 9x63 is the next step up for a pair of "astro" binoculars. Notice, that if you take the second number (the size of the main lens in millimeters) and divide it by the first number (the power) you will get what is known as the "exit pupil" in millimeters ( 56mm / 8=7mm ). For an "astro" binocular an exit pupil value of around 7mm is ideal, this is the size of an average night adapted pupil. (Exit Pupil is NOT the diameter of the eyepiece lens' of a pair of binoculars). If you are a bit older then an exit pupil of 5mm may be better. In any case, a magnification (power) value over 10x makes hand holding very hard as the natural shaking that hand holding introduces is magnified as well. Magnification over 10x will require a tripod mount or an expensive image stabilizer system. •

WHAT I WANT IS A COOL LOOKING SCOPE FOR THE WINDOW SO I CAN IMPRESS MY NEIGHBORS...

This is fun. First, Be honest with yourself! If what you really want fits in this category, the people that you likely wish to impress will not know the difference between a good telescope and a 650x XYZ mart special, so you can save a a lot of money :-). I would get a 70mm refractor with the cool looking German Equatorial Mount (GEM). That would make it a little bigger then your neighbors 60mm scope and it would have a cooler mount to boot. Also a refractor looks like a stereotypical telescope, unlike a Newtonian which will just confuse them ("which end do you look through"). If you need a little telescope for your office or a shelf Orion sells a little tiny brass refractor that would just fit the bill. If you intend to spy on your neighbors (I do not recommended this) then an "alt-az" mount would work better then a GEM, but you will want a 45° diagonal. Just remember, if you get a telescope in this catagory, it will likely be useless when It comes to viewing anything astronomical with it. •

I HAVE A MILD INTEREST IN STARGAZING.

See "I don't know" above. For you binoculars are still the best way to start. But you really think that a telescope is for you, I would have to recommend a Dobsonian. You are the best person to determine what size to get but a nice average size would be a 6" to 8". Dobsonian refers to a Newtonian in a simple "alt-az" cradle type mount. This is best way to maximize your aperture per money spent. A "dob" is easy to use and setup. •

I WANT A GOOD TELESCOPE AND HAVE $XXX TO SPEND. •

Less then $200

Getting a telescope in this price that will not disappoint you is very very unlikely to happen! I must strongly suggest that you buy a good pair of binoculars. Orion sells very nice binoculars in the $150 dollar range. In the same way that it is suggested to avoid cheap telescopes, It is best to

avoid cheap binoculars ( less then $80 - $90). While the cost of acceptable telescopes has been getting lower over the last few years DO NOT BE FOOLED! •

$200 - $400

You just might find a usable telescope in this range. Some examples of good scopes in this range would be dobsonians sold by Orion and others, as well as some of the smaller Meade ETX models. I have some personal experience with the Meade ETX-70 model and I can actually recommend it for many people, if you can find one. The ETX-70 has a secret to its success... With the supplied eyepieces, it doesn't have much more power then a pair of binoculars. This was a wise move on the part of Meade. A newer model, the ETX-80AT-TC has been introduced and should have many of the same good qualities. I haven't actually tried one of the new ETX-80's yet, but if it is a larger and improved version of the ETX-70 then it should be worth a look. •

$400 - $800

There are many choices in this range. There have been very good reports about Stellarvue telescopes. Medium sized Dobsonians (8" - 12") can be had in this range (watch out though - they are really BIG) as can some of the more advancedMeade ETX models (I have one of these...). Also the Meade LXD55 series of telescopes have surprised many people with the amount of scope you get for the amount of money – seems that they are worthy of consideration. •

More then $800

I WANT TO DO SOME SERIOUS STARGAZING.

Here is where the number of choices explode! Money becomes more of a limiting factor then the choices available. The simple fact of the matter is that those with lower budgets will need to look at binoculars or Dobsonians. Those with more money will need to consider the size and portability of the telescope of their dreams. Big telescopes are, well, BIG! They can be so big that they will not fit inside the average car. The choices start with larger "dobs" in the 10" and larger range. Many very serious stargazers use large (12.5" to >20") Dobsonians. We then move over into scopes like Schmidt-Cassegrain Telescopes (SCT) and APO refractors. Finally we add computerized "Go-To" capabilities to these bigger APO's and SCT's (and even the "Dobs"). These larger and/or more complex telescopes can take a lot of room and a lot of setup time. If you are like me, you work a normal shift. If the sun sets at 9PM that means that it doesn't get dark until 10 PM or later. If you want to go to bed at midnight and the scope takes an hour to disassemble and put away... Hmmm... You do the math. There is something to be said for getting a simple telescope. •

I WANT TO GET INTO ASTROPHOTOGRAPHY.

First take a look at the Astrophotography for Beginners page. For the sake of this point I will assume that we are talking about long exposure astrophotography. Here the most important thing is not necessarily the telescope but rather the mount. A very high quality mount is a must. Often, quality German Equatorial Mounts (GEM’s) are preferred by astrophotographers. Mounts such as those made by Losmandy, Mountain Instruments, and Astro-Physics are employed by many astrophotographers. These GEM's also have the advantage of being able to accommodate many different types of telescopes. The very capable Meade and Celestron fork mounts work well but you must also use the scope that came with the mount (although you can piggyback a smaller scope on it). Another option may be the Meade LXD55 series of telescopes. If you have even more money you might look at the new Meade LX200R and RCX400 Ritchey-Chrétien models.

I WANT A GOOD SCOPE FOR VIEWING THE PLANETS (Mars, Jupiter, Saturn and the Moon).

Good planetary telescopes have a couple things in common. Contrast and usually a long focal length. Many people feel that the best planetary telescopes are APO refractors. The problem is that any APO refractor is going to be expensive. Lower cost options can include MaksutovCassegrains and “long” achromatic refractors. Schmidt-Cassegrain Telescopes (SCT) can also offer pleasing views of the planets. It is still true that a larger aperture has a higher resolution then a smaller aperture, but you MUST have very steady air to take advantage of it. So, for viewing planets, a larger aperture is not as beneficial as it is for viewing deep sky objects.

The Conclusion... A telescope can be a great thing, or it can discourage you from enjoying a rewarding hobby. The choice is yours. I cannot emphasize enough... DO NOT BUY A CHEAP TELESCOPE!!! If you can get a great deal on a good scope, great, but you WILL waste your money if you get that $149 650x special that may be tempting you. Never even consider a telescope that advertises it power on the box (650x, 725x, 625x60, etc). Why? Well put simply, I have never seen a good telescope that advertises it power on the box.

Telescope FAQ A So, should I buy that cheap scope?

No! The best advice I can give is that you get what you pay for. “Cheap” is a relative term, $149 may seem expensive to you, but worthwhile telescopes cost more. B Should I get a It depends. If you follow the advice to get as much aperture as refractor or a possible for the money you have to spend, then a reflector (mirror reflector? based) is the right choice for 75% of people looking to buy their first telescope. The reasons to get a refractor (lens based) are a bit more complicated. Inexpensive refractors have problems with false color, but they are often more compact and therefore better for traveling. Also, refractors tend to give more pleasing views when used in the daylight. Most reflectors tend to be very large by comparison, but will have better light gathering capability. C Should I get a There are arguments for and against computerized “GOTO” scopes. computerized First, those computers cost money that could be used toward “GOTO” telescope? sturdier mounts or better optics. Second, some feel that if you use a “goto” scope you will never learn the sky because you will never have to hunt down any objects. The other side goes like this, First, The cost of the scopes is coming down all of the time, and “GOTO” scopes cost no more then the earlier “non-goto” version did (the ETX90-EC vs. the ETX90-RA is a good example of this). Second, many people would give up trying to find a deep sky object before they ever found it without “goto”. For some it’s the hunt, for others, it’s the observing, the choice is yours… D Why is aperture so Two reasons, light gathering and resolution. A 10 inch (25cm) important? telescope can gather 4 times the light of a 5 inch (12.5cm) telescope. Seeing conditions permitting, a 10 inch telescope has twice the resolution of a 5 inch telescope. Example, Under perfect skies, the galaxy M51 looks like two smudges in a 3.5 inch

telescope. In a 6 inch telescope, the spiral structure of M51 is just visible. In a 10 inch telescope the spiral structure is clearly evident. In a 25 inch telescope, fine detail of the spiral arms is clearly visible, as is the molecular cloud that surrounds the galaxy!