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

April 10, 2018 Comments off

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 and Callisto woodcut

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

Arcas and Callisto

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

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04/09/2018 – Ephemeris – Follow the arc to Arcturus

April 9, 2018 Comments off

Ephemeris for Monday, April 9th. The Sun will rise at 7:09. It’ll be up for 13 hours and 11 minutes, setting at 8:20. The Moon, 1 day past last quarter, will rise at 4:40 tomorrow morning.

The fourth brightest night-time star is now up in the east. It is Arcturus, a bright star with an orange hue. It can be found otherwise by finding the Big Dipper and tracing out and extending the curve of the handle and remembering the line “Follow the arc of the handle to Arcturus”. To remember the name of the star and how to find it. Arcturus is about 37 light years from us and is moving quite rapidly across the sky, compared to most stars, though one would not notice it to the naked eye in one’s lifetime. Arcturus is slightly more massive than our Sun, and about 7 billion years old, and is entering its red giant stage of life after using all the hydrogen fuel in its core. Our Sun, being slightly less massive will survive on hydrogen a bit longer.

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

Addendum

Arc to Arcturus

Look high in the east on a spring evening to follow the arc of the Big Dipper’s handle to Arcturus. Created using Stellarium ans GIMP.

Categories: stars Tags: ,

04/06/2018 – Ephemeris – Marking the passage of 13 hours of daylight

April 6, 2018 Comments off

Ephemeris for Friday, April 6th. The Sun will rise at 7:14. It’ll be up for 13 hours and 2 minutes, setting at 8:16. The Moon, 2 days before last quarter, will rise at 2:33 tomorrow morning.

Tomorrow morning early, the crescent Moon will pass Saturn and Mars. These planets will be below the Moon in the dark early morning hours. The dark night hours will be increasingly more inaccessible as summer approaches. Today we’ve broached 13 hours of daylight. By the summer solstice on June 21st the Sun will be out just a bit over 15 and a half hours. Meaning that the Sun will be down for only eight and a half hours, with only three and a half hours of really dark sky, Moon permitting, between the end of evening astronomical twilight and the beginning of morning astronomical twilight. Twilight is really long around the summer solstice because the Sun sets at a shallow angle.

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

Addendum

Definitions

End or start of Civil Twilight:  Sun is 6° below the horizon

Brighter planets become visible

End or start of Nautical Twilight:  Sun is 12° below the horizon

Brighter deep sky objects can be found for public star parties

End or start of astronomical twilight:  Sun is 18° below the horizon

On moonless nights, the twilight glow is gone and the sky is dark

04/05/2018 – Ephemeris – Hydra, a constellation for all of spring

April 5, 2018 Comments off

Ephemeris for Thursday, April 5th. The Sun will rise at 7:16. It’ll be up for 12 hours and 59 minutes, setting at 8:15. The Moon, 3 days before last quarter, will rise at 1:41 tomorrow morning.

In the southern evening sky can be found the constellation of Hydra the water snake. Unlike the monster of the same name this Hydra has but one head, which is its most distinctive part. At 10 p.m. look to the south. The head of Hydra is located below a line from Gemini and Leo. It is directly below Cancer the crab, and left of the star Procyon. Hydra’s head is a small distinctive group of 6 stars that make a loop and the snake’s slightly drooping head. At that time the sinuous body of Hydra sinks below the horizon in the southeast. As it gets later in the evening the rest of Hydra will wend its way to eventually end beneath Libra the scales. This can also be seen in the next few months as Hydra slithers across the southern horizon.

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

Addendum

Hydra finder

Hydra the water snake finder animation for 10 p.m. April 5th.. Hydra is the longest of all the constellations. Click on image to enlarge. Created using Stellarium and GIMP.

04/04/2018 – Ephemeris – Wednesday is bright planet day on Ephemeris

April 4, 2018 Comments off

Wednesday, April 4th. The Sun will rise at 7:18. It’ll be up for 12 hours and 56 minutes, setting at 8:14. The Moon, half way from full to last quarter, will rise at 12:44 tomorrow morning.

Let’s take our weekly look at the bright planets. We’re down to 4 the naked eye planets are visible now. One is in the evening sky. Venus will be visible low in the Western twilight from about 8:40 p.m. until it sets at 10:01. Mercury is in the morning sky, but too close to the Sun to be seen by anybody. Jupiter will rise late this evening at 11:16 p.m. That doesn’t make it an evening planet. It has to rise before sunset to be an evening planet. Saturn will rise at 2:59 a.m., while Mars will rise 14 minutes later at 3:13 a.m. At 6 tomorrow morning these three planets will be strung across the southern sky. Bright Jupiter will be in the southwest, dimmer Mars and Saturn will be in the south-southeast, with Mars below Saturn.

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

Addendum

Venus in twilight

Venus in evening twilight at 9 p.m, tonight April 4, 2018. Click on the image to enlarge. Created using Stellarium.

Morning planets and the Moon

The morning planets and the Moon at 6 a.m. April 5, 2018. Click on the image to enlarge. Created using Stellarium.

Binocular Moon

The waning gibbous Moon at 6 a.m. April 5, 2018 as it might be seen in binoculars.

Telescopic planets

The morning planets as seen by a telescope using the same magnification for all at 6 a.m. April 5, 2018. a.m. Jupiter’s moon Io is in the planet’s shadow. See the table below from Project Pluto. Created using Cartes du Ciel (Sky Charts).

Moon Event             Date     Universal Time   Local time   
Io : Eclipse start     5 Apr 2018  9:04 UT        5:04 EDT
Io : Occultation end   5 Apr 2018 11:57 UT        7:57 EDT (unseen)
Planets and the Moon at sunset and sunrise of a single night

Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on April 4, 2018. The night ends on the left with sunrise on the 5th. Click on the image to enlarge. Created using my LookingUp program.


 

04/03/2018 – Ephemeris – How to spot Zodiacal Light

April 3, 2018 Comments off

Ephemeris for Tuesday, April 3rd. The Sun will rise at 7:19. It’ll be up for 12 hours and 53 minutes, setting at 8:12. The Moon, 3 days past full, will rise at 11:44 this evening.

Zodiacal light is a faint but towering glow that can be seen after the end of astronomical twilight on a moonless night. It is seen in the west in the evening in late winter and early spring and in the east in the morning in late summer and early autumn. The axis of the glow is the ecliptic, the plane of the Earth’s orbit, indeed that of all the planets, along which lie the constellations of the zodiac. Right now the end of twilight is about 10 p.m. and advancing at a rate of a minute or two each night. The cause of zodiacal light is dust, micron sized dust from comets and asteroids. Most of these lie in the plane of the solar system, which is why zodiacal light is centered on the ecliptic and the constellations of the zodiac and increases in brightness and width toward the Sun.  Spotting Zodiacal Light takes dark adapted eyes,  time and patience.

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

Addendum

Zodiacal Light

Much enhanced Zodiacal Light from the my back yard at 9:31 p.m. March 16, 2018, 5 minutes after the official end of astronomical twilight. Canon EOS Rebel T5 18mm f.l., f/3.5, 6 sec. ISO 12,800 . The clouds on the left appear to be illuminated by the lights of the towns of Beulah and Frankfort 20+ miles away.  Note the Pleiades at the top of the image.

 

04/02/2018 -Ephemeris – Mars is appearing to pass Saturn in the morning

April 2, 2018 Comments off

Ephemeris for Monday, April 2nd. The Sun will rise at 7:21. It’ll be up for 12 hours and 49 minutes, setting at 8:11. The Moon, 2 days past full, will rise at 10:40 this evening.

At 3:02 this afternoon the planet Mars will pass the planet Saturn. The event is called a conjunction, which simply means they are on nearly the same line of sight from the Earth, and nothing more. It will make a pretty sight tomorrow morning before the sky gets too bright with reddish Mars being just below Saturn, by a bit less than 3 moon widths. Conjunctions of these two planets occur at intervals of two years give or take, since it involves the orbital motions of Mars and Saturn while viewing them from a third planet also orbiting the Sun.

Currently both planets are moving eastward against the stars. Saturn will slow and stop its motion on April 18th, while Mars will continue until June 28th. They will track westward for a while. This is because the Earth will be passing these planets this summer, which is called opposition (from the Sun).  Saturn will reach opposition on June 27th, Mars on July 27th.  Mars closest approach will occur four days later at a distance of 35.76 million miles  (57.59 million kilometers).  This is Mars’ closest approach to the Earth since August 27th, 2003.  Expect the return of the Mars hoax emails this summer.

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

Addendum

Conjunction animation of Mars passing Saturn

Conjunction animation of Mars passing Saturn at daily intervals at 6 a.m. for March 30 to April 4, 2018. This will occur above the Teapot asterism of the constellation of Sagittarius. Created using Stellarium and GIMP.

I covered the Mars hoax 5 years ago here on an August 27th when Mars was nowhere close to us.