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Epslon-Lyra Also know as
a Telescope: What kind of telescope should I buy?
and a simple guide for those buying their first telescope.
Last Updated: 11/20/2011 2:04 PM
www.my-spot.com > Astronomy
> Buying a Telescope Advice
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 than
$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...
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...
If you do not have
much money (say not more than $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 than 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!!!
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 be very
expensive. That means that most of us will be looking at a mirror based
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.
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 than 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.
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 than 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
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 than you want to spend.
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
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 than 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 than 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 many places sell a little tiny brass refractor that would
just fit the bill. If you intend to spy on your neighbors (I do not
recommended this) an "alt-az" mount would work better than 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.
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 than $80 - $90). While the
cost of acceptable telescopes has been getting lower over the last few
years DO NOT BE FOOLED!
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 (I
own one) with the now discontinued 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 than a pair of binoculars. This was a wise move on
the part of Meade. A newer model, the I haven't actually tried one of the ETX-80's yet, but if it is a larger and improved version of the
ETX-70 it should be worth a look.
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 advanced Meade ETX models (I have one of these...). Also the
Meade LXD75 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.
See the next
- I WANT TO DO SOME
Here is where the
number of choices explode! Money becomes more of a limiting factor than
the choices available. The simple fact of the matter is that those with
lower budgets will need to look at binoculars or lower end 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
such as those from Obsession and James Grigar's Astro
(Note: A very close friend of mine ordered a 14" dob from Astro Sky and
could not be happier! It took some time to get but it truly is a fine
scope - I own a custom pier from James and have used my
Astro Sky dob and can say from experience that it is a piece of art.
Please consider this as an endorsment from a couple happy
customers). We then move over into scopes like Schmidt-Cassegrain Telescopes (SCT) and APO
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
- I WANT TO GET INTO
First take a look at
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, Mathis 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 LXD75 series of
telescopes. If you have even more money you might look at
the Meade LX200-ACF or the new Celestron EdgeHD Aplanatic
- I WANT A GOOD SCOPE
FOR VIEWING THE PLANETS (Mars, Jupiter, Saturn and the Moon).
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 Maksutov-Cassegrains and
“long” achromatic refractors. Schmidt-Cassegrain Telescopes (SCT) can also offer pleasing views of the
planets but with less of that highly touted contrast. It is still true
that a larger aperture has a higher resolution than 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.
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.
should I buy that cheap scope?
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.
I get a refractor or a reflector?
depends. If you follow the advice to get as much aperture as possible
for the money you have to spend, a reflector (mirror 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.
I get a computerized “GOTO” telescope?
are arguments for and against computerized “GOTO” scopes. First, those
computers cost money that could be used toward 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 than 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…
is aperture so important?
reasons, light gathering and resolution. A 10 inch (25cm) 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!
Of course there are many many advice sites for
beginners, some of which are in the links below, However, I strongly
recommend viewing the Interview with Timothy Ferris on PBS's Seeing in the Dark website.
The four interviews take a little less than an hour to view.
You will also enjoy watching the Seeing in the Dark film.