04/28/2022 – Ephemeris – The story of Arcas and Callisto

This is Bob Moler with Ephemeris for Thursday, April 28th. Today the Sun will be up for 14 hours and 6 minutes, setting at 8:44, and it will rise tomorrow at 6:35. The Moon, 2 days before new, will rise at 6:16 tomorrow morning.

Appearing in the eastern sky at 10 p.m. tonight is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite which is horizontal to the left, pointed to by the arc of the handle of the Big Dipper, higher in the east. The Big Dipper is the hind end of the constellation Ursa Major, the Great Bear. In one story, Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young woman who had the misfortune of being loved by god Zeus. Zeus’ wife, Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into a bear. Arcas, many years later, unaware of why his mother disappeared, was about to kill the bear when Zeus intervened and placed them both in the sky, where he continues to chase her across the sky nightly.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Boötes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center

08/19/2021 – Ephemeris – Jupiter is at opposition today!

This is Ephemeris for Thursday, August 19th. Today the Sun will be up for 13 hours and 51 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, 3 days before full, will set at 4:11 tomorrow morning.

Tonight, Jupiter will be at opposition. That’s a shortcut term for Jupiter being opposite the Sun in our sky. At that time, Jupiter rises at sunset and sets at sunrise. It is also at its closest to us. It also officially becomes an evening planet, available in the evening for those of us with daytime jobs. In even small telescopes, Jupiter shows two dark bands. There’s more, but those two are the most prominent. Its four largest moons will be visible before 9:50 pm tonight, after that the innermost of the four, Io, will start to cross the face of Jupiter. It will leave Ganymede on Jupiter’s east side. On the west side will be the moon Europa, and farther out, Callisto. At 12:08 am, Io will reappear on the west side of Jupiter, joining Europa and Callisto. The moons do put on a show.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Jupiter’s Galilean moons at two times tonight, August 19th at 9:30 pm (01:30 on the 20th, UT) and 12:30 am (04:30 UT). From 9:50 pm to 12:08 am (01:50 – 04:08 UT), Io will pass in front of Jupiter and be practically invisible. Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).

08/04/2020 – Ephemeris – Viewing Jupiter and its moons with binoculars or small telescope

This is Ephemeris for Tuesday, August 4th. Today the Sun will be up for 14 hours and 30 minutes, setting at 9:03, and it will rise tomorrow at 6:34. The Moon, 1 day past full, will rise at 10:06 this evening.

The planet Jupiter is a fine object to view with just about any optical aid be it a pair of binoculars, spotting scope or telescope. In binoculars, if held steady or mounted on a tripod Jupiter itself will no longer look star-like, but a tiny disk. Several of Jupiter’s moons can also be seen. With a telescope four of them can be seen, the same four Galileo discovered 410 years ago. At 10 pm they will be in the same order of distance from the planet that they actually are. The two nearest will be on the west side of the planet Io the closest, the Europa the next moon out. On the east side there is the third farthest Ganymede, and farthest out is Callisto. Their orbits are nearly edge on to us, so they shuttle from one side to the other of the planet.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and its Galilean moons for tonight and tomorrow night August 4 & 5, 2020. Those moons really move from night to night. This is shown north at the top, east to the left. Based on telescope design the image presented could be inverted, mirror image or both. Created using Cartes du Ciel (Sky Charts).

Due to the lack of time (59 seconds) I could only cover the moons. I’ll address Jupiter’s cloud features at another time. Can’t wait? Here’s a link: https://bobmoler.wordpress.com/2018/05/22/05-22-2018-ephemeris-seeing-detail-on-the-face-of-jupiter-with-a-small-telescope/

04/13/2020 – Ephemeris – The story of Callisto and Arcas or Ursa Major and Boötes

This is Ephemeris for Monday, April 13th. Today the Sun will be up for 13 hours and 25 minutes, setting at 8:26, and it will rise tomorrow at 6:59. The Moon, 1 day before last quarter, will rise at 3:09 tomorrow morning.

Appearing mid way up the sky in the east at 10 p.m. is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom-right of the kite, pointed to by the arc of the handle of the Big Dipper, above it. In one Greek myth Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods. Zeus’ wife Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into an ugly bear. Arcas, unaware of the events surrounding his mother’s disappearance in his youth was about to kill the bear when Zeus intervened and placed them both in the sky to save her. To this day Boötes continues to chase the Great Bear, Ursa Major, around the pole of the sky each night.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center

04/26/2019 – Ephemeris – The story of Ursa Major and Boötes

Ephemeris for Arbor Day, Friday, April 26th. Today the Sun will be up for 14 hours even, setting at 8:41, and it will rise tomorrow at 6:39. The Moon, at last quarter today, will rise at 3:39 tomorrow morning.

Seen in the east at 10 p.m. tonight is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite to the right. It is pointed to by the arc of the handle of the Big Dipper, higher in the east. Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods. Zeus’ wife Hera, found out about it, and since she couldn’t punish Zeus, turned the poor woman into a bear. Arcas, many years later, unaware of the events surrounding his mother’s disappearance was about to kill the bear when Zeus intervened and placed them both in the sky to save her, as Arcas still pursues her across the sky nightly.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center

04/10/2018 – Ephemeris – How Boötes and the Great Bear got into the sky

Ephemeris for Tuesday, April 10th. The Sun will rise at 7:07. It’ll be up for 13 hours and 14 minutes, setting at 8:21. The Moon, 2 days past last quarter, will rise at 5:14 tomorrow morning.

Appearing mid way up the sky in the east at 10 p.m. is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom-right of the kite, pointed to by the arc of the handle of the Big Dipper, above it. In one Greek myth Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods. Zeus’ wife Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into an ugly bear. Arcas, unaware of the events surrounding his mother’s disappearance in his youth was about to kill the bear when Zeus intervened and placed them both in the sky to save her. To this day Boötes continues to chase the great bear Ursa Major around the pole of the sky each night.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

04/25/2016 – Ephemeris – Arcas and Callisto

Ephemeris for Monday, April 25th.  The Sun rises at 6:41.  It’ll be up for 13 hours and 59 minutes, setting at 8:40.   The Moon, 3 days past full, will rise at 11:56 this evening.

Appearing mid way up the sky in the east at 10 p.m. is the kite shaped constellation of Boötes the herdsman.  The bright star Arcturus is at the bottom of the kite, pointed to by the arc of the handle of the Big Dipper, above it.  In one story Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods.  Zeus’ wife Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into an ugly bear.  Arcas, unaware of the events surrounding his mother’s disappearance was about to kill the bear when Zeus intervened and placed them both in the sky to save her.  To this day Boötes continues to chase the great bear Ursa Major around the sky each night.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center

04/12/2016 – Ephemeris – Can you tell the Jovian moons apart without a program?

Ephemeris for Yuri’s Night, Tuesday, April 12th.  The Sun will rise at 7:02.  It’ll be up for 13 hours and 21 minutes, setting at 8:24.   The Moon, 1 day before first quarter, will set at 2:22 tomorrow morning.

It’s the 55th anniversary of Yuri Gagarin’s flight as first human to orbit the Earth.  Speaking of orbits, we can see Jupiter’s 4 largest moons orbit that planet in small telescopes.  Their orbits are nearly edge on to us, so they seem to move back and forth from one side to the other of the planet in pretty much a straight line.  So how can you tell them apart without a reference?  The four moons from Jupiter in order are Io, Europa, Ganymede, and Callisto.  They are not normally arranged like that.  Ganymede is the brightest and Callisto the dimmest, and is usually the farthest away.  Io is usually the closest appearing and has a slight reddish hue due to its sulfurous volcanic surface, and Europa is the dimmer moon close in to Jupiter.  Io also can be seen to noticeably move in an hour.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

One of my old pictures of Jupiter. Callisto is obvious from its far left position and dimmer brightness. On the right, the farthest is Ganymede due to its brightness and position. Inside of it is Europa, again, dimmer than Ganymede and inside position is probably Europa. That leaves Io, which may be trying to duck behind Jupiter, as a bump in the left edge of the planet.

Jupiter and its moons as simulated by Cartes du Ciel for tonight, 10 p.m. April 12, 2016. The bodies, from let to right are Ganymede, Callisto. a background star, Jupiter, Io, and Europa.

02/19/2015 – Ephemeris – Jupiter is beginning to take its rightful place as king of the evening sky

Ephemeris for Friday, February 19th.  The Sun will rise at 7:37.  It’ll be up for 10 hours and 38 minutes, setting at 6:16.   The Moon, 3 days before full, will set at 6:10 tomorrow morning.

Jupiter is becoming noticeable in the evening sky in the east after 8 p.m.  The heavy atmosphere near the horizon make telescopic observations difficult because the planet and its satellites will appear fuzzy and have color fringes top and bottom.  Wait an hour or two for the planet to rise higher into quieter and thinner air to get the best telescopic views.  Jupiter is accompanied by four moons in telescopes.  Tonight they’re on one side of Jupiter, with Io closest, then Europa and Ganymede close to each other, while Callisto as usual appears to be the farthest satellite.  The face of Jupiter itself is crossed by dark belts and light zones that run in the same direction as the satellites orbit.  The moons change position from night to night.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter, the Moon and stars tonight at 10 p.m., February 19, 2016. Created using Stellarium.

This image is shown smaller than actual size.  Image expansion lately hasn’t worked.  If you are using Firefox, right-click on the image, and then click on View Image.

Jupiter and its moons tonight, 10 p.m. February 19, 2016. Created using Stellarium.

Jupiter and its four Galilean moons. The planet has to be over exposed to pick up the moons. But the eye can handle the brightness difference with no problem. This is one of my old pictures I do believe.

Jupiter with its Great Red Spot November 18, 2012 by Scott Anttila.

The above image by Scott Anttila is actually much better that the image seen in small telescopes.  Advances in digital photography and processing allow the stacking and averaging of many images to create better pictures by  amateur astronomers with modest equipment than the best telescopes of a quarter century ago.

04/14/2015 – Ephemeris – Arcas and Callisto

Ephemeris for Tuesday, April 14th.  The Sun will rise at 7:00.  It’ll be up for 13 hours and 25 minutes, setting at 8:26.   The Moon, 3 days past last quarter, will rise at 5:08 tomorrow morning.

Rising in the eastern sky at 10 p.m. tonight is the kite shaped constellation of Boötes the herdsman.  The bright star Arcturus is at the bottom of the kite, pointed to by the arc of the handle of the Big Dipper, overhead.  In one story Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief Greek god.  Zeus’ wife Hera, found out about it, and since she couldn’t punish Zeus, turned Callisto into an ugly bear.  Arcas, unaware of why his mother disappeared in his youth was about to kill the bear when Zeus intervened and placed them both in the sky.  Now Arcas as Boötes chases the Great Bear forever around the pole of the sky each night.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

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