On Saturday evening (Oct. 8), should local weather conditions permit, you'll be able to enjoy a view of a waxing gibbous moon hovering near to the "king of the planets," Jupiter.
Both will be posed about one-quarter up in the east-southeast part of the sky as darkness begins to fall. The moon, which will be less than 24 hours from full phase — 99-percent illuminated by the sun — will be situated just below and to the left of Jupiter, a distance measuring roughly 4 degrees.
To gauge how wide 4 degrees is, your clenched fist held at arm's length is equal to roughly 10 degrees. So, Jupiter and the moon will be separated by less than half a fist on Saturday night. In addition, the moon measures one-half degree wide. However, because of an optical illusion, the moon actually appears twice as big as it actually is to our eyes. Thus, while the separation between the moon and Jupiter seemingly should be equal to eight moon widths, when you see them in the sky on Saturday evening, the two will appear to be much closer — to some, perhaps less than half the predicted "eight moons wide" distance.
And yet, you don't really need the moon to identify Jupiter; it readily attracts attention all by itself. With Venus currently deeply immersed in the glare of the sun and out of view, Jupiter has taken over as the brightest object in the night sky, save for the moon.
For the moment, Jupiter ranks as the second brightest object in the night sky and does not set just before 6:00 a.m. local daylight time. As twilight fades it is soon joined by the bright stars of early autumn. When you sight the moon and Jupiter on Saturday for instance, don't overlook one of the landmarks of the sky, the Great Square of Pegasus.
Jupiter may be the best planet for amateur astronomers to observe; viewers with the smallest telescopes or even steadily-held binoculars will be able to identify its bright moons, and its disk shows more illuminated surface area than all the other planets combined.
For those with large telescopes of 6-inch or greater aperture, its cloud belts are readily visible as well as the famous Great Red Spot (GRS), a giant storm that has been raging on the planet for several hundred years.
An assiduous planet observer, Christopher Go of Cebu in the Philippines, has provided Space.com with an absolutely incredible image he recently shot (on August 27th) of Jupiter, using a QHY462C, camera which clearly shows the Great Red Spot crossing the planet's disk.
Mr. Go notes: "Transparency [atmospheric clarity] was very poor, but there was excellent seeing [a very steady image]!"
And one final thought: If clouds hide your view of the moon and Jupiter on Saturday, don't worry: They'll be together again on Friday, Nov. 4th.
If you're looking for a telescope or binoculars to observe the moon or the planets in our solar system and don't know where to start, our guides for the best binoculars deals and the best telescope deals now can help. And if you're interested in taking your skywatching photography to the next level, make sure not to miss our best cameras for astrophotography and best lenses for astrophotography guides.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium (opens in new tab). He writes about astronomy for Natural History magazine (opens in new tab), the Farmers' Almanac (opens in new tab) and other publications. Follow us on Twitter @Spacedotcom (opens in new tab) and on Facebook (opens in new tab).