Based on the latest national forecast, skies will be mainly clear tonight (Oct. 31) across the western half of the United States, as costumed kids arrive at the door looking for candy or some other Halloween treat. 
Space.comBy Joe Rao  
©  Gowrishankar L. | Halloween Night Sky 2019: Don't Miss These Celestial Treats
Generally speaking, anywhere west of a line running from Duluth, Minnesota, down to Del Rio, Texas, should have generally clear skies, accompanied by unseasonably cold temperatures. Farther east, unfortunately, a developing storm system near the lower Great Lakes will bring widespread cloudiness and rain to much of the eastern U.S., although parts of Florida and the Southeast could luck out with dry, fair weather.  
If you plan to accompany children around your neighborhood, you might want to enlighten them by pointing out some of the objects that will be visible in the sky. Better yet, if you have a telescope, give your visitors a treat of a different kind: Give them a close-up view of some celestial sights, starting with the moon and two bright planets.

"King of the planets" and the "Lord of the Rings"

Jupiter and the moon will be the first objects to vie for attention as they descend the southwest part of the sky. The moon will be in a waxing crescent phase, nearly four days past new, and located 4 degrees to its lower right will be the king of the planets, Jupiter. It glimmers into view during twilight, and with even a small telescope using low magnification, you'll be able to see its disk as well as all four of the famous Galilean satellites, so named because Galileo Galilei was the first to see them with his own crude telescope in 1610. On this Halloween night, you'll see one satellite all by itself on one side of Jupiter — that will be Ganymede — while the other three reside on the other side of Jupiter. 
Two of the three moons huddled together on one side of Jupiter, Europa and Io will appear very close together, while the other, Callisto, will appear the closest of the four relative to Jupiter. 
Of course, the crescent moon is a telescopic showpiece in itself, and once the sky becomes sufficiently dark, you'll likely be able to see what is sometimes referred to as "the old moon in the new moon's arms," otherwise known as Earthshine. This is when the portion of the moon that isn't illuminated by sunlight glows with a faint, yet readily detectable bluish-gray glow — almost as if the moon were some translucent ball being illuminated from within. 
Tell your young visitors to pretend that they are astronauts on the moon's surface. If they were on that part of the moon where the bright crescent is, the sun would be in the sky illuminating the lunar landscape, but if they were on the dark part of the moon, there would be no sun. Rather, what would be in the sky would be a nearly full Earth, appearing almost four times larger than the moon appears to us. Sunlight reflecting off the clouds and oceans would make our earth appear dozens of times brighter than the full moon, and that Earthshine would light up the surrounding mountains and craters on the moon with an eerie blue-gray glow. That's why we can glimpse the dark part of the moon on Halloween night.
Saturn is another planet to look for, situated about 17 degrees to the upper left of the moon. Your clenched fist held at arm's length measures about 10 degrees in width, so roughly 1.5 fists to the moon's upper left will be a bright, solitary yellow-white "star," perhaps the most beautiful of all the planets. Its rings are still wide open, with the north face tilted some 25 degrees to our line of sight. But if you hope to show off the moon, Jupiter and Saturn to trick-or-treaters through a telescope, do it as soon as it gets dark, because later in the evening their images likely will be shivering and churning about, due to poor viewing quality near the horizon. Jupiter and the moon set about 2.5 hours after sunset, while Saturn will stay in the sky about 1.5 hours longer. 

Halloween fireballs

One good reason to keep a sharp eye on the sky on Halloween night is for the possibility — albeit small — of catching a view of a spectacular fireball meteor. The objects in the Taurid meteor shower, sometimes called the "Halloween fireballs," begin showing up in mid-October and continue into mid-November. The Taurids don't produce a lot of meteors — may be a dozen during an hour's watch at the very most, and usually much less. But so far as the Taurids are concerned, it's quality that's important, not quantity.
Meteors — popularly referred to as "shooting stars" — are generated when debris enters and burns up in Earth's atmosphere. In the case of the Taurids, they are attributed to debris left behind by Encke's Comet, or perhaps by a much larger comet that, upon disintegrating, left Encke and a lot of other rubble in its wake. Indeed, the Taurid debris stream contains noticeably larger fragments than those shed by other comets, which is why this particular meteor stream occasionally delivers a few outstandingly brilliant meteors known as "fireballs." If one of these flares across the sky on Halloween night, it might even make the kids temporarily forget about candy!

Helpful hints for young telescope viewers

In the September 2019 issue of The Astronomical League Magazine Reflector, author Richard W. Schmude Jr. offers some tips for those who plan to do public outreach for astronomy on Halloween:
"Firstly, children sometimes grab or touch the eyepiece, so use an inexpensive one. I gently warn children not to touch the telescope. In my area, parents have learned to tell their children not to touch the telescope. In some cases, a child will grab the eyepiece, causing the telescope to shift. For this reason, a Dobsonian telescope with a good finderscope is a good choice for Halloween outreach. A small stool or booster ladder may help very small viewers. Sometimes, parents hold their children up to look through the eyepiece. One may also place a monitor-connected video camera in the telescope and people can easily see the object on a screen. Finally, I have my bag of goodies next to my telescope so that the children get two treats!"
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