Fall is a great time to be outside, even after the Sun goes down. Be sure to check out our list of celestial events you’ll be able to see during the month of October. It will be an exciting month for viewing the planets, meteor showers, and two full Moons! Be sure to bookmark this page and refer to it all month long!
Take note that we sometimes will use angular degrees to define the separation between two objects, such as (for example) a bright planet and the Moon. Keep in mind that the width of your clenched fist, held at arm’s length, measures roughly 10°. When we speak of magnitude, we are referring to the brightness of an object, the lower the figure of magnitude, the brighter the object. The brightest stars are zero and first magnitude. Under a dark, clear sky, the faintest objects that you can see with just your eyes are fifth or sixth magnitude. Objects with negative magnitudes are the brightest. Sirius, the brightest star, is -1.4. Venus can get as bright as -4.8. A full Moon is -12.7 and the Sun is a blindingly bright -26.7.
All times are listed as Eastern Daylight Time for the Northern Hemisphere.
October 1—Mercury reaches greatest elongation, 26° east of the Sun. But this zero-magnitude planet is also positioned well south of the Sun in our sky, so from northern latitudes it sets only ¾ hour after sundown and is nearly impossible to see. From the Gulf Coast states and the Southwest, however, Mercury will be somewhat higher, sets a bit later, and might be sighted with the unaided eye.
October 1— Full Harvest Moon at 5:05 p.m. named as such because it’s the full Moon occurring nearest in the calendar to the autumnal equinox. Usually it’s the September full Moon, but this year it came much too early (on September 2nd). There are other versions of this rule that the Harvest Moon is the full Moon that comes either on or after the equinox, which, more-often-than-not would also put it in October. Farmers utilize the full Moon’s light at this time of the year by working late into the night by the light of the Moon. And for a while, instead of rising its average of 50 minutes later each night, it rises only about 24 minutes later.
October 2—Call tonight “M&M” Night (Moon and Mars). Look due east at 8:30 p.m. local daylight time and you’ll see the Harvest Moon, and shining like a fiery beacon to its upper left will be Mars. As the night wears on, watch how the Moon slowly creeps (at its own diameter each hour) eastward to just below Mars by around midnight. By the time dawn is breaking the following morning, you’ll see the Moon descending the western sky, with Mars now sitting to the Moon’s lower right.
October 3—Venus shines as a brilliant Morning Star in the east during dawn. It rises about 3½ hours before the Sun at the beginning of the month, and 3 hours before the Sun at month’s end. This morning it is closely paired with first-magnitude Regulus in Leo. Venus will be within 2½° of this 1st-magnitude star from October 1st through 5th, but on this morning, they are separated by only ½°, with Venus, burning 150 times brighter, sitting just below it. Throughout this period, some of us may notice an enhancement of their subtle colors because their contrast is more obvious when they’re near each other. The hint of yellow in Venus and touch of blue in Regulus will be quite a sight to the unaided eye.
October 6—Mars arrives at its closest approach to Earth at 10:18 a.m. EDT, when the distance will be 38,586,816 miles; reflected sunlight from the planet will traverse the distance to the Earth in 3 minutes 27 seconds. It will not come this close again until the year 2035. Viewing Mars through a telescope with an 80X eyepiece will cause the planet to appear the size that the Moon looks to the unaided eye. Since its south pole is inclined toward the Earth, Mars’ polar cap should be visible even in small telescopes.
October 9—Last Quarter Moon at 8:39 p.m. In this phase, the Moon appears as a half Moon due to the direct sunlight; the illuminated part is decreasing toward the new Moon phase.
October 13—Mars arrives at opposition to the Sun, visible from dusk to dawn and shining at a head-turning magnitude of -2.6 —three times brighter than Sirius! After reaching this pinnacle, Mars will recede from Earth and gradually become dimmer through the remainder of the year. This close approach will be unusually favorable for observers in the United States since the planet will literally soar high in our sky—nearly 60° up at 1 a.m. local daylight time for most northern U.S. cities.
October 14 —Set your alarms! Check out the eastern sky at around 5:30 a.m. local daylight time and you’ll see the slender sliver of a waning crescent Moon, just 2½ days before new, and hovering well to its upper right will be Venus. Despite their rather wide separation, it will be an eye-catching sight for early risers.
October 16 —New Moon at 3:31 p.m. In this phase, the Moon is not illuminated by direct sunlight and is completely invisible to the naked eye. The Moon is also coming to within 4½ hours of the perigee point in its orbit. In fact, the Moon’s distance on that day is 221,775 miles, which is only 3 miles farther away than it was on April 7th, the so-called “Supermoon.” This new Moon will cause an unusually large range of tides, which could be especially problematic if a tropical cyclone threatens the coast. Some might even prefer to brand this unseen Moon as a “proxigean” Moon, because of its proximity to the perigee point in its orbit.
October 21–22—This is a fine year to watch the Orionid meteor shower, which is expected to peak early this morning in a moonless sky. Past displays have yielded 10 to 20 meteors per hour under similar conditions, especially during the wee hours before dawn when the constellation Orion dominates the south-southeast sky. These meteors tend to have dusty trains, and a few Orionids may be seen up to a week before and after maximum.
October 22—As darkness falls this evening, look toward the south-southwest sky for a broad triangle formed by the Moon, Jupiter, and Saturn (magnitude +0.6). Jupiter will be situated 4° to the Moon’s upper right, while Saturn will be nearly 5° to the Moon’s upper left. Jupiter stands watch in the south-southwest at dusk to the upper left of the Teapot of Sagittarius. The big planet is lower and a little more distant than it was in summer, but next to Mars, it’s the brightest star-like object in the evening sky. Saturn, meanwhile, stands in the south at dusk. The Summer Triangle of Vega, Deneb, and Altair points down at it from on high like an arrowhead, but Saturn shines coolly with a steady yellowish glow, in marked contrast to the stars’ twinkling.
October 23—First Quarter Moon at 9:23 a.m. In this phase, the Moon looks like a half-Moon in the sky. One-half of the Moon is illuminated by direct sunlight while the illuminated part is increasing, on its way to becoming a full Moon.
October 25—Mercury passes inferior conjunction (between the Earth and the Sun) and then rapidly enters the morning sky.
October 25—For the second time this month, the Moon pays Mars a visit, although they more widely separated (4° apart) as opposed to their last encounter on Oct. 2nd. Mars is also 4 million miles farther away and consequently now appears about 28% dimmer, yet still dazzling at magnitude -2.1.
October 31—Rare full Halloween Blue Hunter’s Moon at 10:49 a.m. Popular culture regards the second full Moon occurring in a month as a “Blue Moon.” And traditionally— in Algonquin Indian lore—the full Moon that comes after the Harvest Moon is known as the Hunters’ Moon, when hunters tracked and killed their prey by autumn moonlight, stockpiling food for the coming winter. Read more about this Halloween Blue Moon here!
But in addition, this particular full Moon comes within less than a day of apogee—its farthest point from Earth—252,522 miles away. So, this full Moon is 14% smaller than in April, the antithesis of a “super” Moon, or as the mainstream media calls it, a “Micro” Moon. And this all happens on Halloween!
So, get ready to finish out October with a “Rare Halloween Micro Hunters’ Blue Moon.” Wow, that’s a mouthful!
By Farmers’ Almanac Astronomer Joe Rao. This calendar is adapted from “Skylog,” a regular feature appearing in Natural History magazine written by Mr. Rao since 1995.