Welcome to
"Binoculars 101"
I am
assuming you are thinking about purchasing binoculars,
otherwise you wouldn’t have navigated to this page. There
are many things to consider before buying. I hope the
following information will help you choose the correct
instrument for your situation.
Things to consider:
1.
Are they
primarily going to be used for astronomy?
2.
Are they
going to be used just by you and/or other family members?
3.
Do you
wear glasses?
4.
How old
are you?
5.
How much
have you considered spending.
6.
Who you
purchase them from.
There are basically two types of binoculars.
Which one is best for Astronomy?
Sleek and Straight - Lite and Compact
but they produce a slightly dimmer image
and are more expensive because of the
precision required for assembly.
Good for wildlife viewing; birds, animals, etc.
Not my first choice for astronomy
.
Bulkier and Heavier
but they have high quality glass with Bak-4 coating.
Multi-coating or fully multi-coating available
which reflects light resulting in brighter images.
Costs less then roof prisms and are the most popular.
This type is my first choice for astronomy.
When
considering coatings, the key here is COLOR.
When you
look in the objective end of the binoculars (this is the
large end) check to see what color is reflected. White
means there isn’t any coating - purple or blue is partial
coating - green is usually fully coated. Fully coated is
the best, because it reflects more of the light through the
eyepiece, resulting in a brighter image. Bottom line, green
coating is your best choice.
Size does make a difference. The more
power, the larger your target, but, the greater the power,
the more movements are exaggerated. Another words, when you
increase your power over 10, you will need to support the
instrument with a tripod or some type of binocular mount to
keep the image from shaking in view. In astronomy that is
critical.
You will also want your objective lens (the large end of
the binoculars) as large as possible. The larger your
objective lens, the more light gathering power you have.
This is important when looking at the sky, because most
objects are dim and very small.
So
whats the best size? Opinions
vary somewhat, but 7x50's seems to be the choice to start
with. The 7, representing power, is small enough to hold
steadily on your target, but large enough to give you some
spectacular views over the naked-eye. The 50, representing
the objective lens which gathers light, is adequate for a
hand-held instrument. The larger the power and objective
lens, the heavier the binoculars become. This is an
important factor to consider, if other smaller family
members will be using them. 10x50's are also a good choice,
but they are on the border of being hard to stay on an
object without hand or arm quivers and they also narrow
your field of view.
One of the advantages of using binoculars is the wide field
of view. You should try not to sacrifice that value.
As a general rule, 'zoom' binoculars should be avoided,
because they have little application for astronomy and the
optics are usually inferior to other comparably
fixed-magnification binoculars.
The
next thing to consider is AGE.
I’m not
talking about the age of the binoculars, but the age of the
user. Whether we like it or not, as we get older, our eyes
don’t work as good as they used to. Maybe you have already
realized that.
When it comes to the eyes, the younger they are, the
quicker they adapt to light and dark. They dialate sooner
and more completely. When considering this process, to
properly match your age to the instrument, you need to
purchase the binoculars that best matches your
exit pupil (or
light leaving the eyepiece). Too large and the exit pupil
lowers the contrast between faint images.
Determine the exit pupil by
dividing
the objectives diameter by the power.
7x50's - 50 divided by 7 = 7.1mm exit pupil
10x50's - 50 divided by 10 = 5mm exit pupil
People under 30 can use 7mm exit pupil
People over 30 should use 5 to 6mm exit pupil
Good eye relief could
also be important
especially if you wear glasses.
Be sure to check with the seller for eye relief.
15 to 20mm eye relief is good for eye glass wearers.
Orion Telescopes and Binoculars offers
retractable
eye cups on many of their products. If your the only
family member that wears glasses, this option provides
an easy solution for those who will share the use of
the binoculars.
What
about optical alignment? This
usually isn’t a factor if you buy from a reputable dealer,
but if it's a private party or pawn shop you need to check
for alignment. The easiest way to check this is to look
through the binoculars with both eyes, cover one eye, then
quickly uncover that eye. If you see two separate images,
don’t buy them.
Other
things to consider when buying used; Focusing , Scratches,
Stains and Dust. Make
sure the center focus turns smoothly and doesn't wobble.
Check the individual eyepiece adjustments for smoothness
and proper function. If there are any lens scratches,
internal dust or stains, they could interfere with
astronomy viewing. If you have any concerns of the items
mentioned above, don't consider buying them for any
significant amount of money. They may be all you want for a
child too young to care for them properly.
Center
hinge should adjust for
whomever is going to use them. If your eyes are wide apart
and other users aren’t, make sure they will adjust inward
far enough to be used.
Should
have a tripod socket. Even if
they can be hand-held steady enough, there may be times you
will want to put them on a tripod. There should be a
threaded hole on the bottom of the center hinge.
What
about price? To get a
good quality pair of binoculars, 7x50's or 10x50's, you
should expect to pay around $150 to $200. To some that may
seem expensive, but over a 10 to 20 year period a good
quality instrument, fitted to your specifications and
needs, $150 to $200 will end up being a bargain.
When
purchasing binoculars, 'Try Befory You Buy' is
recommended. However,
if you haven’t a reputable vendor nearby, you can purchase
by mail order or via the internet. Just remember to check
their return policy.
I have purchased almost everything through the internet or
by catalog. I've always had good experience with every
company I’ve dealt with. Companies like Orion Telescopes and
Binoculars,
Discovery
Telescopes, Big
Binoculars.com, Shutan Camera, Meade, T & T
Binocular Mounts and JMI Telescopes are
just a few that have been outstanding to work
with.
If you have any questions, don't hesitate to e-mail me
at l.wenzel@mchsi.com
or call 618-663-3002