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Observing tips for July 4th, 2018 July 2, 2018

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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The forth of July brings a lot of people outside after dark. While you’re waiting for those fireworks to begin, here are a few things to look for.

I recommend taking along a pair of binoculars.

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Venus and Mercury in the West July 3, 2018, 9:30 PM.

Start about half an hour after sunset (or about 9:30 in SE Michigan) and look west. About 20º ( 2 sideways fists) above due west is Venus. As the skies darken, it stands out like a beacon! look 16º (index finger to pinky) down and to the right for Mercury. Mercury can be a tough object to spot because it’s never far from the Sun, so it’s never visible in really dark skies. The first map is for July 3, 9:30 PM in Ann Arbor, but should be good for the 4th as well.

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Jupiter and Saturn in the south at 10 PM July 4

Fireworks usually begin around 10 PM (especially if you’re farther north.) Get a seat facing south for some of the summer’s best celestial show. Jupiter is about 30º above the southern horizon, and Saturn about 10º up in the SE. While you’re looking that way, be sure to check out Scorpio and Sagittarius too. Bright Antares, the heart of the scorpion, falls between Jupiter and Saturn right now.

With binoculars or a small telescope, you can pull in the 4 brightest moons of Jupiter. They’ll be lined up in a tight row on the 4th, which helps make it easier to pick them out at low magnification.

From left to right, Io, Europa, Jupiter, Ganymede, and Callisto

The Galilean Moons of Jupiter at 10 PM July 4, 2018.

If you actually have a small telescope and can pull your eye away from Jupiter, check out nearby Zubenelgenubi, a nice double star whose name means “southern claw” because it was once considered part of Scorpius.

Saturn is sitting on the top of the teapot. If your skies are dark enough later in the evening, you’ll be able to see the Milky Way trailing up the sky next to it. With binoculars or a small scope, the rings should be visible, if only as a strangely oblong shape. Some of the brighter moons may also be visible, though they aren’t nearly as easy as Jupiter’s moons.

From left to right, Iapetus, Rhea, Saturn, Tethys, and Titan, which is actually much lower that the other moons.

Saturn and its moons, July 4, 2018 at 10 pm

It’s early days yet for Mars, but if you’re out past midnight, look back to the same are Saturn was at 10 PM. Mars rises ESE around 11 PM, so it’s up nearly 10º in the SE at midnight. It’s the brightest thing in that area right now, and only getting brighter, so if your skies are clear, it’ll be hard to miss. Keep an eye on it the rest of the month as it moves toward closest approach on July 31!

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Elusive Mercury in the Evening December 1, 2017

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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This weekend promises amazing weather for December in SE Michigan. Take advantage of it by looking for the elusive planet Mercury!

Sunset on December 1 in A2 is at about 5:03 PM, and Mercury sets at about 6, so grab a pair of binoculars and go out between roughly 5:15 – 5:45 and look low in the SW. Be sure to check out Saturn too: it’ll disappear behind the Sun soon! The image below is for 5:30 on Friday December 1, 2017

As the days progress, Mercury gets closer to the Sun in the sky (yes, it’s in retrograde), so by the 5th or 6th it’ll be all but impossible to catch! Conjunction is on the 12th. Saturn conjunction is December 21. 01Dec1730SW_Mercury.png

Cassini’s Legacy September 11, 2017

Posted by aquillam in Astronomy, MichiganAstro, Science.
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As the Cassini mission comes to an end, NASA and JPL ponder what its legacy will be.

When the mission started, I had just recently started working as the outreach coordinator for Michigan Astronomy, and the presentations I did about it were some of the first of my career here.

My how the time flies.

Saturn Opposition 2017 June 16, 2017

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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It’s summertime, and that means Saturn-time!

But why is that?

A year on Saturn is a bit more than 29 years on Earth, which means Saturn moves about 12º along the ecliptic each year. For comparison, the Moon moves about 15º per day, so in a whole year, Saturn’s position will change less than the the Moon changes in a single day! It fact it’s so little that it take Saturn an average of two years to move through each zodiac constellation. Last year Saturn crossed the boundary into Ophiuchus (between Scorpio and Sagittarius), and it won’t leave until December. That means Saturn will be visible in the evening at about the same time this year as it was last year.

Ophiuchus is often called the 13th zodiac because itt sits between Scorpio and Sagittarius

Saturn takes 29 years to make a complete circuit of the ecliptic

Of course 12º isn’t nothing. Each year opposition drifts just a little farther east along the ecliptic, so the date changes. And since there are 360º in a circle and 365 days in a year, the date corresponds to roughly a degree per day! This year, opposition was June 15th. In 2016, it was June 3, and in 2015, May 23. Next year, opposition will be June 27.

By the way, opposition is when something (like Saturn) is opposite something else (like the Sun) in the sky. So when Saturn is at opposition, it rises at sunset, then sets at sunrise. Each night it rises a little earlier, so the weeks following opposition are the best time for evening observers to get a look. Closest approach is always close to opposition too, so the planet will be bigger and brighter than usual.

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At opposition, the Sun, Earth, and outer planet are on a line with the Earth in between.

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Because the orbits aren’t circles, the Earth may get closer to the outer planet a few days before or after opposition.

 

So enjoy summertime Saturn while you can. In about 4 more years, it’ll be fall when Saturn’s out.