Binocular astronomy is rather easy to carry out and is also a lot of fun. Binoculars are relatively inexpensive and are eminently portable. Employing both eyes simultaneously definitely adds to the visual experience.
Binoculars are ideal for showing the "big picture". These instruments can readily display objects that are too large to fit into the fields of view of most telescopes. In addition, binoculars can often be useful in "surveying" the area where an object is located prior to conducting a telescopic star-hop.
A surprising number of celestial objects, including many binary stars, open and globular star clusters, nebulae, and some of the brighter galaxies, can be detected with binoculars. Scanning through the heart of the Milky Way with a binocular from a dark site is a very memorable experience.
I recommend purchasing a 10x50 (i.e., 10 power and 50mm aperture) binocular for astronomical use. A 10x50 binocular is usually not overly heavy for most people to hand-hold and provides a 5mm exit pupil that will be appropriate for most observers when age and observing site darkness are taken into account*. People who must wear eyeglasses while observing may want to look for a binocular with at least 14mm of eye relief. Browse http://kingston.rasc.ca/Library/rasc-binoculars.pdf and http://binocularsky.com/binoc_basics.php for tips on choosing binoculars.
There's more on binocular performance at http://www.wwnorton.com/college/astronomy/astro21/sandt/powerbinocs.html
A chart showing the effects of magnification and aperture on binocular performance is posted at http://www.wwnorton.com/college/astronomy/astro21/sandt/images/pabin2.gif
A three part evaluation of three different binocular apertures can be found at the following URLs:
In my opinion, the best binocular observing guides available are Touring the Universe through Binoculars by Philip S. Harrington, Binocular Astronomy by Graig Crossen & Wil Tirion, Binocular Highlights: 99 Celestial Sights for Binocular Users by Gary Seronik, and Observing the Night Sky with Binoculars by Stephen O'Meara.
Phil Harrington discusses various targets monthly in his Cloudy Nights Binocular Universe column at http://cloudynights.com/category.php?category_id=182 and in a quarterly column in Astronomy. He offers an excellent freeware planetarium program known as TUBA (Touring the Universe through Binoculars Atlas), which also includes information on purchasing binoculars, at http://www.philharrington.net/tuba.htm
A number of articles on observing with binoculars are posted at http://www.skyandtelescope.com/community/skyblog/stargazing/86589452.html
Tips on binocular astronomy are available at the following sites:
A video on observing with binoculars is posted at http://www.youtube.com/watch?v=wAnAZz-ZPJ0
This website discusses a number of deep-sky objects that can be seen through binoculars. http://www.starman.co.uk/book/hba-home.htm is another binocular astronomy site worthy of consulting. See http://astrogeek.wordpress.com/2007/07/18/binocular-objects/ for a long list of binocular targets; http://www.deepsky.info/other/Binocular%20Targets.PDF is another list. A few more good objects are mentioned at http://www.backyard-astro.com/deepsky/bino/homeb.html
My monthly lists of binocular deep-sky objects are posted at http://cs.astronomy.com/asycs/forums/t/48393.aspx
A list of binocular objects is included with each monthly Evening Sky Map at
The Astronomical League's Binocular Messier, Deep Sky Binocular, and Southern Sky Binocular lists include many of the best binocular deep-sky objects:
Sketches of a number of deep-sky objects as seen through binoculars can be found at http://rodelaet.xtreemhost.com/binocular_astronomy.html
Mounting a binocular on a tripod, or better still, a dedicated binocular mount (guider) will improve views markedly. An informative pdf on binocular mounts is posted at http://www.cloudynights.com/documents/thoughts.pdf
* An excellent explanation of exit pupil can be found at http://www.nikon.com/products/sportoptics/how_to/guide/binoculars/basic/basic_05.htm