Many nights, my moongazing time is limited to a few minutes, which is precisely when binoculars are the instrument of choice.
I have a houseful of telescopes — it’s an occupational hazard that comes with building them — and yet I use binoculars most frequently to look a the Moon. Why? In a word, convenience.
Backyard astronomy always seems to involve a balance between reward and effort. For example, a telescope delivers all kinds of lunar detail, but you have to set it up first, and for most of us, that means several trips in and out of the house. If you use a Newtonian reflector, you may also have to align the optics and wait for the scope to cool down. Hardly a recipe for a quick look.
Binoculars, on the other hand, provide nearly instant observing with minimal effort. You simply grab ’em and head outside. Sure, when it comes to the Moon, the rewards aren’t as great as those you’ll get when looking through a telescope, but with binoculars, you can take advantage of brief viewing opportunities. And you’ll find the more often you look, the more you’ll see.
Binocular views of the Moon are limited mainly by the low magnification, typically in the 7× to 15× range. Even so, binoculars can reveal craters only a few tens of kilometres across and, at the same time, let you take in the big-picture view and appreciate the relationship between the dark lunar seas (maria) and the bright, heavily cratered highland regions. I also enjoy seeing the Moon amongst the stars, especially when the lunar disc is passing near or even through the Pleiades star cluster or other rich star fields.
I like to scan the Moon with binoculars when it’s full or nearly so, when conditions are ideal for seeing the feathery rays that radiate from craters such as Tycho and Copernicus. I find it a fun observing challenge to try to trace the full extent of these rays. Full Moon is also a rewarding time to look for subtle tints and shading in the large maria. Have you ever noticed how Maria Serenitatis and Tranquillitatis are slightly different shades of grey? And, if you look carefully, you’ll see plenty of surprisingly small craters, which appear as little bright spots on the dark maria.
Seeing the maximum amount of detail generally requires two things. First, you must scan along the day/night line, called the terminator, to see craters and other features in stark relief. Second, you have to hold your binoculars steadily. Sit in a comfortable chair, preferably with elbow support, or secure the binos on a tripod to improve the view substantially, although at the expense of some convenience.
My favourite lunar binos are Canon’s 15×45 image-stabilized binoculars. The image-stabilization feature really greatly reduces jiggles from hand-holding the glasses, and the magnification is enough to show plenty of detail. (Canon no longer makes the 15×45s, but its newer 15×50 and 12×36 models are excellent as well — you can find a review of the entire line here.)
With image-stabilized binoculars, I don’t need a tripod to get the most out of the views. Often, I use these binoculars to assess the steadiness of the seeing conditions and to determine what features are situated along the terminator before deciding whether I want to set up a telescope. Most of the time, though, I just enjoy the view for what it is.