Buying a Telescope: Suggestions for
Newcomers
For Starters
My first suggestion is the same as many other people's: Go visit
an astronomy club or a public star party and ask the people there.
Folks at public star parties are usually quite friendly and will
often let an interested person try out their scopes for a little
while. Once you've seen how different types of scopes behave (how
they move, what they show, how easily they are set up and put
away), you'll have a much better idea of what you want.
Additionally, I highly recommend getting familiar with the night
sky. Learn the major constellations; be capable of recognizing a
dozen or so when the sky is clear and there isn't much moonlight.
If you have a pair of binoculars, even little 25mm "pocket" models
you take to football games, spend some time exploring the night sky
with them. You'll be surprised at what you can see, and you'll
learn more about how to observer things without even being aware of
it.
A good beginner's scope will have the following features,
regardless of price, design, or accessories:
- Easily set up. Not too big, too heavy, or too complex.
Ideally, it's something you can take outside in one trip, at most
two, and then set up in just a few minutes.
- Reasonable quality. To an extent, you get what you pay
for, but even fairly inexpensive scopes will perform well if
competently designed.
- Good for a wide range of targets. After you get some
observing under your belt, you'll have a better idea of what kinds
of objects you like to observe. At the beginning, though, you'll
want something that shows pleasing views of a wide range: the major
planets, double and multiple stars, and at least the brighter star
clusters and nebulas.
- Good basic accessories. At a bare minimum, you will
want at least 2 eyepieces (ideally, 3) and a finding device of some
sort. Many scopes only come with 1 eyepiece, and some inexpensive
(but otherwise perfectly good) scopes come with an inadequate
finder. If your prospective purchase lacks some of these items,
you'll want to budget some extra money for them.
Some Things I Suggest
Given all this, I generally make two suggestions to new
observers:
- A 6" (150mm) or an 8" (200mm)
Dobsonian reflector
- A 4" / 100mm medium to long focus refractor (roughly,
f/ratio of f/8 to f/12)
At the moment (mid-2003), good vendors of the Dobsonians are
Orion
Telescopes and Discovery. For the refractors, look at Orion
Telescopes as well, and then look at any dealer that carries
Celestron or Meade telescopes, such as Astronomics,
Anacortes,
or Oceanside Photo
and Telescope. For higher but still fairly reasonable prices
(about 75-100% more than Orion, Celestron, or Meade), Stellarvue is a
fairly new refractor manufacturer with a very good reputation.
I have a definite bias towards the reflectors. The extra
aperture really makes a big difference, even (I might say
especially) from a light-polluted city. Don't believe what
people might say about light pollution being worse in larger
apertures than in smaller ones. Under given conditions, whether
light or dark, larger telescopes will show fainter objects, and
normally greater detail in bright ones. Also, the Dobsonian style
of mounting and aiming a telescope is straightforward, and
beginners can quickly learn their way around the constellations
with one.
However, they have a few minor drawbacks. In particular,
reflectors of all types require occasional maintenance to give
sharp images. I don't find reflector maintenance to be a big
hassle, but not all observers are alike.
Hence, my second suggestion, a 4" or 100mm refractor. With a
good small refractor, you will end up with very sharp images with
little or no tweaking. Also, assuming equal optical quality,
refractors can produce slightly brighter images than other
scopes of the same aperture; modern multi-coated refractor lenses
generally transmit more light than the combinations of mirrors used
in reflectors. This difference is fairly small (10 - 20%
typically), but still enough to be worth noting.
Refractors of a given aperture are significantly more expensive
than other types of telescopes, and usually larger and heavier, so
it's hard to get as much aperture on a budget. A good 6"
Dobsonian might cost $400; a cheap 6" refractor will cost
twice as much, and be much bulkier and harder to use. So, for
refractors, I suggest a smaller, more manageable scope. For many
people, having a scope that requires next to no maintenance is a
significant plus, worth some loss of aperture. If this is the case,
then a 4" refractor would make a good starting scope. If it's not,
and you want to get the most bang for your buck, stick
with the Dobsonians.
A Little Off the Beaten Path
- Cash-Savers: The scopes I describe above will cost at
least $300 to $500. If you are really strapped for cash, you can
get a slightly smaller scope such as an 80mm refractor or a 4.5"
Dobsonian. There are some very good deals out there. For example,
Orion sells two 4.5" Dobsonians, a larger (f/8) model for $200 and
a smaller (f/4) model (called the "StarBlast") for only $160. Both
of these would make an acceptable starting scope for a person on a
budget.
- Catadioptrics: Another possibility, which is a little
more expensive for a given aperture, is a catadioptric
telescope. This is just a telescope that uses both lenses and
mirrors to form the image. Usually they have a large mirror in the
rear, like a reflector, and a large corrector lens at the front. I
don't recommend them as much for beginners as the other two
designs, because most catadioptrics have very long focal ratios
(f/12 to f/15), making them less suitable for wide field views than
the other scopes I've described. Also, they tend to be relatively
expensive for the aperture. A 5" catadioptric might cost $600; for
the same $600 or so, you can get a 10" Dobsonian that will be
generally more powerful all around. They are, however, incredibly
compact for the aperture, so someone who really wants or needs an
especially portable telescope, and plans to observe things like
double stars or planets most of the time, might want to consider
one.
- For the Ambitious: Finally, if you know that
amateur astronomy isn't just a passing fancy, and have some extra
cash to spare, push my suggested aperture limits a little further.
Try looking at a 10" Dobsonian, a 7" or 8" catadioptric, or a 120mm
(4.7") refractor. This is as big as I'd go with a first telescope,
and in any event, try a scope in this size range before buying. A
10" Dobsonian is probably the largest medium-cost scope you can fit
in a typical car, for instance. Refractors larger than 4", of
conventional length (over f/8), are much bigger than they
seem in a photo.
Some Things I Don't Suggest
- Department-Store Hobby-Killers: Avoid the small (50mm
and 60mm) refractors that sell for $150 or so in the department
stores. These almost invariably have poor eyepieces, hopelessly
inadequate finders, and a wobbly mount and tripod. For just another
$150 to $200 you can get a much better quality telescope
that will serve you well for years.
- Very Small Refractors: Actually, don't get a 60mm
telescope from anywhere. For only a small amount more money, you
can get a larger telescope that will show much more.
- Small Reflectors: Ones smaller than 4" / 100 mm. Just
don't; very small reflectors tend to be rather poorly made.
- Pseudo-Catadioptrics: Any telescopes that appear to
have a corrector lens built right into the focuser (as opposed to a
true catadioptric, which has a corrector lens at the front of the
tube). These are almost always a disaster. Some ultra-short
reflectors, including some sold in department stores on online
shopping centers, use this design. Unfortunately, some otherwise
reputable vendors, such as Orion Telescopes, sell scopes like this.
- "Short Tube" Refractors: Usually 80mm to 120mm, with
an f/ratio under f/8. These actually aren't poor scopes, just
rather specialized ones that are sometimes a little oversold. They
are optimized for low-power, wide-field views of things like star
clusters and big nebulas. They are not very good for planets, which
are important targets for all observers, particularly new
observers from a city. Also, all inexpensive short-focus refractors
suffer from color distortions at high magnification. This can get
annoying on the Moon and planets in a hurry.
This last rule is not as absolute as the others. It can be bent if
you plan to do terrestrial observing as well as astronomy, for
example; the ubiquitous 80mm f/5 short tube refractor easily mounts
on almost any camera tripod, making a nice spotting scope too.
Also, wide-field telescopes complement larger scopes, especially
those over about 8", very nicely. In particular, there are always
nights where you want to observe something, but don't want
to set up the "big" telescope. You may want to consider a
short-tube refractor as your next purchase, after your
first telescope.
And Finally, Don't Forget
A few other things you might want to get, depending on your
experience and the scope you get:
- Eyepieces. You'll want at least two. A very general
guideline: have at least one eyepiece that magnifies about 6-8
times per inch of aperture (for low powered, wide-field views), and
another that magnifies about 15-20 times per inch (for medium- to
high-power views of things like planets and double stars). You'll
eventually fill in the gaps as you get more experience. For
example, if you observe the planets a lot, you'll probably want to
get an even higher powered eyepiece (say, 30 power or more per inch
of aperture); if you enjoy wide-field views, you might want an
ultra-low power eyepiece (one giving 3-4 times per inch).
For scopes of the sort I suggest as beginning scopes, you don't
need expensive, wide-field designs like Naglers or Panoptics (of
course, go ahead and buy them if you really do want them and have
the money). Plössls and Orthoscopics will be fine, and you'll
save a bunch of money (cost: $40-$80 per eyepiece).
- Finder. If your scope has a 40mm or larger finder
scope, it's probably enough for now. Otherwise, you may wish to
upgrade. If your scope has no finder, you'll want to get one soon.
Trying to find objects by sighting along the tube gets to be a
royal pain in a hurry. Either a magnifying finder scope (looks a
bit like a rifle scope) or a "unit power" finder like the Telrad or
Rigel Quickfinder will do, though I recommend trying both before
purchasing, since most folks have a preference for one type or the
other.
- Star charts. You'll need these to find anything
besides the planets and the brightest stars.
I have some guidelines and suggestions for accessories elsewhere on this site.
Last Modification: Dec 5, 2003
