Jim's Corner Blog

Binoculars and Backyard Astronomy

An important piece of equipment for observing stars and deep sky objects in the amateur astronomer’s arsenal is the binocular. Armed with star atlases, or for the more technically oriented a smartphone or tablet app, and binoculars, the stars and deep sky objects can be hunted down among the constellations, the Milky Way, and star fields. The binocular offers the widest field of view available to the backyard astronomer, with lightweight convenience and ease-of-use.

For experienced observers, the binocular is an optical tool that allows for wide-angle viewing of star fields, up-to-6º or 7º of field-of-view. An amazing amount of night sky observing can be observed with binoculars, particularly when searching and discovering stars and deep sky objects that can only be seen with the wide field-of-view that a pair of binoculars can provide. Many of deep sky objects can be easily scooped up by a binocular sweep. Seeing the stars and deep sky objects in relationship to the sky around them will put that object in its proper context in the sky.

Most backyard astronomers hand hold their binoculars for observing. To obtain the steadiest images, the preferred technique for hand holding binoculars is to hold the ends of the binocular barrels, instead of gripping them around the binocular body where the prisms are located. This technique works well for both 7×50 or 10×50 binoculars. This handheld method is especially effective with the larger 12×60, 15×70 or 16×70 binoculars.

The larger 80-mm or 100-mm binoculars require the steadier support of a tripod or parallelogram binocular mount.

Observing in a bean bag chair is a comfortable and steady way to observe the night sky with hand-held binoculars. Nestle into the bean bag with binoculars in hand, with the elbows resting on the bean bag sides as they puff up from your weight . The binocular images will be steady from the support! This is an easy and comfortable way to observe the night sky with binoculars, and cheaper than some of the parallelogram binocular mounts or other forms of binocular mounts. This technique has been used by me successfully with binoculars up to 15×70’s.

Diametrically opposite from the aforementioned 50-mm, 60-mm and larger binoculars are the new pocket-sized low power 2.1×42 binoculars. Some of our members have looked through my pair of 2.1×42 at some of our outreach star parties. The 2.1×42 binoculars are small, lightweight, and provide an extremely wide field of 25º field-of-view. Easily carried for backpacking adventures or just a quick peek at the sky in the backyard, these binoculars can be used to scan constellations and large star fields. The night sky seems to come to life with the 2.1×42, giving the user the feeling of having 42mm aperture eyeballs. Don’t let the very slight field curvature bother you, the wide-open expanse of view easily outweighs this slight aberration. stars and deep sky objects comprising of open clusters or nebula clouds appear small due to the low magnification, but are still easily seen and identifiable, and are set in their stellar surroundings. stars and deep sky objects separated by tens of degrees can be captured by this diminutive optical tool. Although slightly aperture-lite, these are fantastic for hunting down stars and deep sky objects in clear Shenandoah country skies with little or no light pollution.

On the other end of the scale are the giant binoculars with apertures of 80 to 100 mm, with the rare 125-mm behemoths. The larger apertures of these giant binoculars do enhance light-gathering ability, but at the cost of convenience, portability, and wide-field-of-view. These large prism binoculars encroach upon the territory occupied by the 80-to-102 mm telescope. With a limited field-of-view of sometimes less than 2.5˚ and needing a sturdy tripod or binocular mount, the wide-field advantage, portability, and ease-of-use of binoculars is lost by using these giant binoculars.

Also, I would be remiss in failing to mention the rare binoculars that use interchangeable 1-1/4” eyepieces. I own two of these bad boys, and will bring them out to one of outings in the future.

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