Thursday, April 22, 2010

What Can I See with: 35mm Binoculars

I have a bunch of different telescopes. They range from 2 inches to 12.5 inches in diameter. But the instrument I use more than any of my telescopes is a pair of 7x35 binoculars.

antique binoculars
My binoculars aren't as good-looking as these, but they work the same way.
My binoculars are light, easy to pack along (they take practically no space at all) are easy to carry along even when I'm not observing near my car (when hiking and so on), and they're easy to share with others.

There's plenty that even a small pair of binoculars can be used to observe. And it's not just sort of generally looking around, either. You can do serious observation with binoculars. Not only that, but binoculars are a perfect helper when you're using a telescope, too.

What Can I See?

In the Solar System

The Moon (and features on it),
Mercury, Venus, Mars,
Jupiter and four of its moons,
Saturn and 2 to 3 of its moons,
Uranus, Neptune,
and about 26 asteroids.
Don't look at the Sun!

Seeing asteroids through binoculars can be a lot of fun. In some cases, they move across the sky quickly enough to make tracking them with a telescope over extended periods of observation difficult. They look like small dim stars, but in some cases you can see their brightness vary as you watch them. You're seeing the effect of the rotation of the asteroid when this happens!


You can see something like a total of 650,000 stars in the sky with a pair of 7x35 binoculars. Now, this is across the whole sky, even the parts you can't see. And, let's face it, not all stars are very interesting. Here are a few of the ones I find most interesting:

  • Albireo, a binary star in the Swan, one amber star and one blue one.
  • Cor Caroli, a binary star in the Hunting Dogs, one is bright, the other dim.
  • O1 Cygni in the Swan, a three-colored triple star
  • delta Scorpii, in the Scorpion, a sextuple star of which you can see three stars
  • Herschel's Garnet Star, a deep red star in Cepheus

A car as a bino mount
The top of a car can provide some stability at a pinch.

Star Clusters

Stars tend to be more interesting in groups. There are two kinds of star clusters, "open" clusters are groups of stars that formed out of the same cloud of gas and dust and are in the process of each going their own way in the galaxy. Globular clusters are like mini-galaxies of stars that are held together by the gravity of the stars.

Globulars are called that because the stars form a sort of "globe" shape due to their gravity. They are among the oldest objects in the universe, and probably have something to do with how our galaxy got its shape. Some of them may be the left-over cores of galaxies that merged with out own.

There are about 100 globular clusters that can be observed with 7x35 binoculars. The dimmest ones are very challenging. I have observed about 55 of them through my binoculars, getting more will take a trip to the southern hemisphere or extremely good sky conditions. When I observe globulars, I look at a few things. How is the light distributed across the area of the cluster? Does it have a tight core, with a faint halo of stars around it, or does the brightness taper off gradually toward the edges? Some are very bright out to the edge, then suddenly dim at the edge. I also look at how tightly bunched the stars appear to be, and the shape (compared to a circle.)

Some of my favorites are:
M22 in Sagittarius, which has a large, bright center and misty glowing edges,
M13 in Hercules which is just plain bright. It's center is bright and it fades out gradually.
M4 is large and misty, covering a large area of sky near Sirius, the Dog star.
M80  in the Scorpion is small and tightly bound.
M55 in Sagittarius is small and bright, with a faint haze around the edge.
M2 is big and bright in the center, fading out rapidly to its edges.
M5 is large and has a large central bright area.

Open clusters are often near nebulas, either gas and dust left over from the material they formed from, or other nearby nebulas in which other new stars are forming in our galaxy.
The trifid nebula has a nearby cluster called M21, for example.
In Perseus, the Double Cluster lets you see two star clusters at once.

Binos on a long neck bottle
A long necked bottle is another improvised bino mount.

Deep Sky Objects

Star clusters are one of the various types of so-called "deep sky objects", which includes nebulas and galaxies. One of the most famous lists of deep sky is the Messier list, named for astronomer Charles Messier. He and his associates were comet hunters. They spent night after night looking for fuzzy-looking patches in the sky, trying to find new comets. Often they would see other things that weren't comets. The Messier list was a list they made of things frequently mistaken for comets.

Now the list is far more useful to amateur astronomers as a list of relatively bright things in the sky that are interesting to look at. There are 110 objects on the list, from stars to galaxies to nebulas. All but three or four are visible through 7x35 binoculars (and if you have excellent skies and are a very skilled observer, you might be able to get all 110!)

Man Made Objects

There are a wide range of man-made objects you can see with your binoculars. For most of them, binoculars are the best way of observing them. You can easily see the space station. In fact, as you watch it you can pick out some of its details, such as the solar panels running crossways to the main boom on which it is built. As it moves, the reflection of the Sun will reveal different parts, such as the habitation sections and heat radiators, if you look sharp.

There are also the Genesis habitat test satellites, which are highly reflective. The Iridium satellites can be very bright, and with binoculars you can follow them through the sky far longer than is possible with the eye when they are dim.

Dusk and dawn are the best times for satellite observing, as you are seeing them when it is dark where you are, but they are still in the sunlight. Polar orbiting satellites are visible all through the night.

a pair of binoculars held on the end of a walking stick.
A walking stick, or tent pole, can hold up a pair of binoculars for astronomy, too.

Sweeping the Sky

One of the best things about binoculars for astronomy is their wide field of view. This lets you look at things that cover too much sky to be seen in a regular telescope. For example, many nebulas cover a large part of the sky, so only a small part of them can be seen through a telescope at any one time. You have to move a telescope around to see it, a piece at a time. With binoculars, however, you can see the whole thing or much more of it. Perseus the Hero and Cygnus the Swan are good constellations to go looking for this sort of nebula.

The Andromeda Galaxy (also known as M-31), is too big to see all at once in a normal telescope. You can see it all at once in binoculars. It covers about five times the width of the Moon in the sky. Under dark skies, you can see its bright heart (nucleus), and the faint cloudy outer parts (the halo.) The edges can be made out in binoculars, where the cloudiness sort of seems to just go away.

And then, there's the binocular's favorite--the Milky Way. With a pair of binoculars you can see the Milky Way like you've never seen it before. Not only can you make out the individual stars, but you can see little knots of brightness in it, and dark patches. The bright areas are nebulas and star clusters buried in the Milky Way. The dark areas are usually dark nebulas that block off the light of the stars behind them.

One particularly interesting area of the Milky Way for binoculars is the area around the constellation of Scutum (the Shield.) This is north and east of Sagittarius the Archer. There are clouds and whorls of stars in this area, as well as cloudy nebulas. With a bit of experience, and taking the time to look with relaxed eyes, you can pick out the details of what you're seeing from the general mass of the Milky Way. The more you learn about what you're looking at, the more interesting it will be to observe. I will often make an effort to remember something that is particularly interesting, then go look it up in a guide to the sky to find out what it was. Later, I can come back and see more detail yet, since I have a better idea of what it is I'm looking at.

Holding Binoculars

In order to see things well, you need to make the binoculars hold still. If they're moving, it's hard to make out what you're looking at and to relax to let your eyes see as much as possible.

hand held binoculars
How to hold binos in your hands to keep them stable.

By Hand

To hold the binos as steady as possible by hand, bring your wrists close together under the binoculars to form a sort of table for them to rest on from the heels of your palms. Then rest your elbows and upper arms against your body to support them. Take in a deep breath, then let it halfway out and hold your breath. Don't strain to hold your breath, just don't breath for a half a minute or so while you look. Then take a breath, and do it again.

With a Support

Placing the binoculars on something makes them far more steady than you can hold them by hand, and you can breath as you please while you do it. Aside from dedicated binocular stands I've supported my binoculars during observation in many ways. A fairly flat tree branch will do. For objects that aren't too high in the sky there's the roof of a car. A long-necked bottle will often sit nicely between the barrels of the binoculars to act as a simple "monopod", or a walking stick can be used.

Halfway In-Between

In some cases you can't rest the binos somewhere and see what you want to see. Then holding them by hand while resting your wrists and the backs of your hands against a steady object will have to do.

Binoculars into Space

Binoculars are great for astronomy, they have a wide field of view that gives a "space walk" experience, they're easy to use, find things with, and take along. They can also help you find things so that you can look at them through a telescope afterward.

They're what I recommend for starting stargazers who are thinking about getting a telescope. It's possible to do serious observing "campaigns" with binoculars, like collecting as many globular clusters or galaxies or Messier objects with them as you can. Using them is great training for learning to see objects in the sky that will pay off with a telescope later. They're cheap, and useful for things other than astronomy.

Check out some of these books on using binoculars for astronomy:

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