We had a question in our last live session about binoculars. Since many of our students may be interested in ways to observe the night sky, I thought I'd make a post about what kind of binoculars are best for this. Binoculars are a great tool for amateur astronomers. They cost less than telescopes, they're easy to tote around wherever you go to observe, and they reveal a lot of the sky that is not visible to the naked eye.
The 2 most important features of binoculars are the magnification, and the objective aperture. When shopping for binoculars, you'll find they're all designated by a set of numbers; for example, 20x60. The first number is the magnification. The second, is the objective aperture. A 20x60 pair of binoculars will magnify what you're looking at 20 times, and each of the big, outer lenses will measure 60 millimeters across.
For nighttime use, you'll need a pair of binoculars with a large objective aperture. The bigger those outer lenses are, the more light you'll be gathering, and the brighter dim objects in the sky will appear. I recommend picking out a pair with
a lens diameter of 50 or more.
However, it is perhaps, more important that you get the right magnification. For handheld use, you can't use a magnification higher than 20. No matter how steady your hands are, they won't be steady enough to allow you to keep the object you're looking at in your field of view if it's magnified too much. Every tiny little movement of your hand will also be magnified. Unless you'll be getting a stand for your binoculars,
keep the magnification between 10 and 15. Generally, for astronomy, magnification is not ever as important as light gathering power.
Therefore, an ideal pair of binoculars for observing the night sky might be 15x70.
And what will you see? Many star cluster that are invisible, or barely visible to the naked eye are easily seen through a pair of binoculars. The best star clusters to try to find are the one's in
Messier's catalogue. Other objects that are great to observe with binoculars, some of which are also listed in Messier's catalogue, include, the Andromeda Galaxy; the Orion Nebula; Coma Berenices; Saturn's rings; the phases of Venus; the Galilean moons of Jupiter; the moon; and, occasionally, comets.
The more you observe the more you'll find to look at. If you have a lot of experience with binoculars, and have any tips or recommendations, please leave comments and share your knowledge.
