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As Geoffrey Chaucer once said, "All good things must come to an end." And the beautiful spread of four bright planets that stretched from horizon to horizon across our summertime evening sky is now coming to its inevitable close.

Venus will be the first to go, dropping into the sunset fires early this month and transitioning to the morning sky by month's end. Jupiter will be next, and while it will not disappear completely, it will spend much of October gradually getting lower in the west-southwest sky, while setting progressively earlier. Saturn is next in line, but for much of this month still remains well positioned for viewing, though by late evening as it nears the horizon, atmospheric turbulence will likely cause its image to become rather shaky. Mars is still a fiery, eye-catching object in the south-southeast at dusk, but continues to fade and grow smaller as it continues to recede from Earth. By Halloween it will shine with only one-eighth of the radiance it displayed in July when it was unusually close to the Earth. Finally, there is Mercury which is very low in the southwest sky all month, but very difficult to perceive until the latter days of the month when it will be in the general vicinity of Jupiter. [Night Sky, October 2018: What You Can See This Month (Maps)]

In our schedule, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm's length measures roughly 10-degrees. Here, we present a schedule below which provides some of the best planet viewing times as well directing you as to where to look to see them.

Very low in the southwestern sky after sunset on Sunday, October 28, bright Jupiter will sit 3 degrees above much dimmer Mercury. The pair of planets will be visible together for several evenings surrounding that date. Mercury will set first at about 7 p.m. local time.
Very low in the southwestern sky after sunset on Sunday, October 28, bright Jupiter will sit 3 degrees above much dimmer Mercury. The pair of planets will be visible together for several evenings surrounding that date. Mercury will set first at about 7 p.m. local time.
Credit: Starry Night software

Mercury — is above the southwestern horizon after sunset during all of October but never high enough to be easily visible. The best time to look is the last week of the month. Use binoculars to scan for it, 45 minutes after sunset. On October 30th, Jupiter (magnitude -1.7) will be hovering about 3 degrees to the upper right of Mercury (magnitude -0.2). Can you glimpse either with the naked eye? Both planets may seem fainter than they are because they are very close to the horizon.

Venus' long evening apparition of 2018 will end as October begins. The very bright inner planet (visual magnitude -4.75) will only be visible during the first week of October, when it will set in the southwestern sky only half an hour after the sun. In a telescope,, it will exhibit a waning crescent that grows in apparent size as the planet moves towards Earth. For the rest of October, Venus will be too close to the sun for observing, passing below the sun in inferior conjunction on October 26. At month's end, Venus will enter the eastern pre-dawn sky.
Venus' long evening apparition of 2018 will end as October begins. The very bright inner planet (visual magnitude -4.75) will only be visible during the first week of October, when it will set in the southwestern sky only half an hour after the sun. In a telescope,, it will exhibit a waning crescent that grows in apparent size as the planet moves towards Earth. For the rest of October, Venus will be too close to the sun for observing, passing below the sun in inferior conjunction on October 26. At month's end, Venus will enter the eastern pre-dawn sky.
Credit: Starry Night software

Venus — enters its beautiful crescent phase for telescope users every time it nears the end of one of its months-long evening apparitions. But this season it’s making its lowest, poorest possible exit from the evening sky (as seen from mid-northern latitudes). As October starts, Venus is technically near its maximum possible brightness at magnitude -4.8, but it appears much dimmer because it’s low in bright evening twilight. This evening it sets about an hour after the sun, but it stands only 9 degrees above the southwest horizon at sunset for viewers around 40 degrees north latitude. And things just get worse after that. If you live in a northern land, you may need a haze free sky or binoculars to detect Venus even on the opening nights of the month. By October 9th, this dazzling world is barely above the horizon in very bright twilight 20 minutes after sunset. Then Venus is lost from view for several weeks as it shuttles toward inferior conjunction (between Earth and the sun) on October 26th, then shoots up gloriously into the dawn sky during early November. 

In the southern sky on the evening of Wednesday, October 17, the first quarter moon will be positioned about 6 degrees to the right of Mars. From dusk until they set at around 1 a.m. local time, the moon's eastward orbital motion (green line) will carry it towards the Red Planet. The following evening, the moon will appear a similar distance from Mars, but now on the left side of the planet.
In the southern sky on the evening of Wednesday, October 17, the first quarter moon will be positioned about 6 degrees to the right of Mars. From dusk until they set at around 1 a.m. local time, the moon's eastward orbital motion (green line) will carry it towards the Red Planet. The following evening, the moon will appear a similar distance from Mars, but now on the left side of the planet.
Credit: Starry Night software

Mars — is still in the south-southeast when twilight ends, and it stays right there at nightfall all month. It is traveling eastward with respect to the stars, or perhaps we should say the stars are sliding westward behind it. It spends all of October moving across the stars of Capricornus, the Sea Goat. As Mars’ distance from us increases from 56 to 73 million miles during October, the planet fades from magnitude -1.3 to -0.6. The telescopic view of Mars, so fine during midsummer, has become relatively mediocre again. In July the red planet was only 3.2 light minutes away from Earth and more than 24 arc seconds across. By the end of October it is more than twice as far and less than half the apparent size. Mars is that very bright, fiery colored object well to the right of the waxing gibbous moon on October 18th.

Very low in the southwestern sky after sunset on Sunday, October 28, bright Jupiter will sit 3 degrees above much dimmer Mercury. The pair of planets will be visible together for several evenings surrounding that date. Mercury will set first at about 7 p.m. local time.
Very low in the southwestern sky after sunset on Sunday, October 28, bright Jupiter will sit 3 degrees above much dimmer Mercury. The pair of planets will be visible together for several evenings surrounding that date. Mercury will set first at about 7 p.m. local time.
Credit: Starry Night software

Jupiter — Shining at magnitude -1.8, Jupiter is still easily seen as October begins. Look for it low in the west-southwest in early twilight. During the final days of the month it will be in the vicinity of Mercury and by October 31st the king of the planets is so low that you’ll probably need binoculars to help you find it. Three days past new phase and just 10-percent illuminated, a slender waxing crescent moon passes a little over 3 degrees north of Jupiter on October 11th.  

After dusk in the southwestern evening sky on Sunday, October 14, the waxing crescent moon will sit less than 2 degrees to the right of Saturn. The pair of objects will be visible together in the field of view of binoculars (orange circle) and will set at about 10:30 p.m. local time. Over the course of the evening, the moon's eastward orbital motion (green line) will carry it past Saturn. Their closest approach of 0.75 degrees, which occurs at 04:00 GMT, will be visible to observers in western North America.
After dusk in the southwestern evening sky on Sunday, October 14, the waxing crescent moon will sit less than 2 degrees to the right of Saturn. The pair of objects will be visible together in the field of view of binoculars (orange circle) and will set at about 10:30 p.m. local time. Over the course of the evening, the moon's eastward orbital motion (green line) will carry it past Saturn. Their closest approach of 0.75 degrees, which occurs at 04:00 GMT, will be visible to observers in western North America.
Credit: Starry Night software

Saturn — is in the south-southwest after dusk and this is probably your last chance to get a good telescopic view of Saturn’s disk, rings, and moons. The planet will remain visible in early evening almost to the end of the year, but it is getting near the horizon where atmospheric seeing wreaks its worst effects – assuming you have an unobstructed view to the southwest at all. The crescent moon has noticeably widened since it visited Jupiter on the 11th, when it passes only 1½ degrees to the right of Saturn on October 14th.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications, and he is also an on-camera meteorologist for Verizon FiOS1 News in New York's Lower Hudson Valley.