Buying Binoculars for Astronomy

I am often asked to recommend a telescope for someone new to astronomy. My answer is invariably, "Don't buy one, buy two -- mounted side by side." In other words, the best first telescope is a binocular.

7x50 or 10x50 binoculars are good general-purpose instruments which are excellent for astronomy, although even the most humble binocular will reveal a wealth of detail invisible to the naked eye. Larger binoculars will need to be mounted on a camera tripod and smaller ones give less bright images, although they can have the advantage of being extremely portable.

There are some things to consider when buying a binocular for astronomy:

You will find that there is a great deal of difference in price, even in binoculars of the same size. Get the best you can afford; they will tend to have fewer faults and give better images. However, the best thing to do is to try some out first. If your local astronomical society holds observing evenings/field meetings, go along and try as many binoculars as you can and solicit as much advice as you can. If you have friends with binoculars, see if any of them suit you.

This post by Marcie Greer to sci.astro.amateur is an excellent introduction to astronomical binoculars from the perspective of a newcomer to their purchase and use for astronomy:

From: Curtis & Marcie Greer <>
Newsgroups: sci.astro.amateur
Subject: Binoculars a Great Way to Start (Long)
Date: Tue, 08 Dec 1998 12:47:29 -0500
Organization: ICX Online, Inc.
Message-ID: <>

While raking the leaves yesterday (I know...but better late
than never), it occured to me that this might be a good time
to share this with the newbie world.

Dear astro newbie:

Binoculars really are a great way to start observing! I
didn't believe it either. I wanted a *real* telesope. I
wanted to see *planets*, but I didn't have the $$ for a
Decent Scope (DS). In fact, I had no idea what a decent
scope was... had never looked through a real telescope (the
little comet spotters don't count).

Everywhere I read to buy binoculars, join a club, try other
peoples DS's and save up for a DS. Knowing I would be
disappointed, but also knowing that I would want binos
anyway, I went ahead and bought binoculars. It was an
excellent decision!

I'm no expert in optics or binoculars, so I chose an
independent shop that I knew  specialized in quality stuff.
You never know, but if you can find a shop with a Celestar
8" Deluxe on the floor, you might be in a good place for
astronomical binoculars. Do not go to Service Merchandise or
Sam's. You really need to be able to have them all lined up
in front of you on the counter and try each one out. You
need a salesperson who knows what is what and is willing to
spend some time standing there while you futz around. Take
your time... I have a hard time with this one. I get excited
and rush things. I spent just over $200 altogether for
binoculars, tripod adapter and cleaning supplies. I could
have easily spent another $75 (at least) on a new tripod and
I probably will when I have the $$. I am using a cheesey
old  tripod. It's flimsey and hard to adjust, but I had it

If you can read up on binoculars for astronomy before hand,
this is a good thing. There are several books available in
most public libraries on binocular astronomy. I checked out
two: The Binocular Stargazer by Peltier and Star Gazing
Through Binoculars by Mensing. Mensing has a good chapter on
testing your binoculars. I have found these books really
useful, esp. since they concentrate on things that are
pretty easy to find, and there's plenty of good stuff to

Even newbies can shop fairly intelligently for binoculars.
There are some basic things that you can look for. First,
don't get the insta-focus. This is a flat bar on the top of
the binos that is used to focus. Get the one that has a
center focusing wheel. Insta-focus is good for birds, but
not stars. You will want to take your time and get a finer
focus for stars. Second, get coated optics. This is pretty
easy to do. Be sure that the eyepiece *and* the objectives
(big lenses) are coated. You can tell by holding them up and
seeing if there is a greenish or golden sheen and they might
say "fully coated" on them. Generally speaking, you will be
looking for 7X50 or 10X50 binoculars.

I tried out 7X50's and 10X50's and liked the 7X50's better
because the field was wider. The ones I ended up with
(Pentax PCF III's) had a 6.2 degree field. In other words,
things weren't magnified as much, but I could see more. I
figured that for my application, this was best and I am
still happy with that decision. The wider field helps me get
from star to star when locating some particular object I
want to view. For instance, I was able to find the position
for M1 even though it was a bit out from any major landmark
stars. The wide field let me creep along from star pattern
to star pattern until I found my target. Besides, more
magnification won't make the stars any bigger. Only planets
and NSO's can be effectively magnified. Generally, you need
a DS for really good viewing of these things anyway.

Once you decide about general things such as the focusing, a
nice case, the cool rubber grips, the rubber eye cups that
fold down (great if you wear glasses) and know which pair
you want, have the clerk get the ones you are planning to
buy out of the box. This is one mistake I made. I spent too
much time looking at the demos and forgot to really inspect
the actual purchase before leaving the store. Fortunately,
it turned out OK, but it just as well might not have.
Inspect the ones you plan to take home! Turn the lenses up
and check to see that there are no scratches or white spots
in the coating. Look for debris inside and bubbles in the
lenses. Look through them at a distant straight line and be
sure it stays straight to the edge of the field. Try out the
wheels and knobs to be sure they turn smoothly. Hold the
binos away from you, towards the light and see if the light
beams coming out of the eyepieces are perfect circles with
no rectangularity. How does the focus look through the
center of the lenses and the edges?  Also ask if you can
return them and for how long and so on. After all you still
haven't seen stars with them!

Tip on using binoculars: move the two halves together until
you see a single circular field; focus with the center wheel
closing the right eye first then do the right eyepiece
focusing with the left eye closed, then do both eyes open
and make minor adjustments.

One more test you can easily do (there are many!) is to take
them outside at night (as soon as possible) and look at a
nice bright star. When it is in good focus, the star should
be a circular pinhole. There shouldn't be rays shooting out
or other funny looking stuff. However, if you have
astigmatism in your eyes and your glasses aren't right, you
might see rays no matter how good the binos. I have to have
my husband's good eyes do the star tests. Also, if you look
at Jupiter (for example) it shouldn't look like a big
florescent purple blob.

Accessories: A decent camera tripod and a binocular adapter
for it. I really like my Pentax adapter, but I will soon
replace my cheesey old tripod. It is much improved since my
husband tied a lead dumbell weight on a cable to the center.
Some newer ones have a hook that you can hang a weight from.
I find the tripod almost essential. If you have the money,
there are some nifty mounts with a boom arm. These would be

Care: don't rub the coatings off. Use a bulb blower (like an
ear syringe or one for cameras with the brush taken off),
microfiber cloth, and liquid cleaner/lens tissue as needed,
in that order. Don't do any cleaning you don't have to. If
it blows off don't wipe it. Keep fingers off the lenses then
you won't have to clean up after them. Don't look at the
sun. Don't poke your eye out. 8^) Read the manual....

A good book will give you more details and other tests, but
this stuff you can do quite easily. Also, a good book will
give you great ideas about projects for your nightly
observing and even some lists. I have found that it is more
fun after a while to have some goals rather than just
ambling around looking at little lights in the sky. All of
this is just my newbie opinion and experience.

Apologies in advance for errors, omissions and wordiness...
Hope this is of use to someone

© 1998 Stephen Tonkin