07/27/2018 – Ephemeris – Mars is at opposition from the Sun today
Ephemeris for Friday, July 27th. The Sun rises at 6:23. It’ll be up for 14 hours and 50 minutes, setting at 9:14. The Moon, at full today, will rise at 9:16 this evening.
The planet Mars was at opposition with the Sun early this morning, that is opposite the Sun in the sky. It is a time when a planet rises at sunset and sets at sunrise. For us it will rise tonight at 9:40 p.m. 26 minutes after sunset and will set tomorrow at 6 a.m., 24 minutes before sunrise. This odd behavior is due to the fact that Mars is actually south of a lime from the Sun through the Earth. Mars’ orbit is tilted to the Earths’ so it will appear lower in the sky as one would expect for a planet in its position. Today Mars is 35.9 million miles (57.7 million km) away. In four days it will be a bit closer to us due to its elliptical orbit taking it a bit closer to the Sun. How much closer? About 93,000 miles (150,000 km) to us.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
This chart is shown with the horizontal being parallel to the ecliptic, which is the horizontal line near the top of the image. Created using Cartes du Ciel (Sky Charts).
Created using Cartes du Ciel (Sky Charts).
Mars on opposition day, July 27, 2018 at 1:55 a.m. as it crossed the meridian due south. In the Interlochen/Traverse City area a bit south of 45 degrees north latitude. Mars appears a an altitude of slightly less than 20 degrees altitude. Created using Stellarium.
Update
Mars at opposition and the full Moon at 2:01 a.m. July 27, 2018. I thought I’d go out near the Mars transit time this morning and photograph the Moon and Mars. Earlier we had a pop-up rain shower, and the clouds were clearing out. Got a lucky shot.
07/26/2018 – Ephemeris – How can you get to Mars – the Hohmann transfer orbit
Ephemeris for Thursday, July 26th. The Sun rises at 6:22. It’ll be up for 14 hours and 53 minutes, setting at 9:15. The Moon, 1 day before full, will set at 6:06 tomorrow morning.
How does one get a spacecraft to another planet, like Mars? One might think to wait until the two planets are closest and zip across. That would take more energy than we are capable of. We cab barely escape the Earth and get a spacecraft into solar orbit. Also one needs energy to slow down to be captured by the planet if one wants to orbit it. The most economical way was devised way before the space age by Walter Hohmann, a German scientist in 1925. The idea is to launch a spacecraft with enough velocity to reach the other planet half way around the Sun, so the transfer orbit is tangent to both the Earth’s and the planet’s orbit. Transit times to Mars would be in the range of 7 months. The InSight lander is currently on such a trajectory.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Hohmann transfer orbit. Credit Planetary Society-Myron Kayton
A Hohmann lowest energy transfer orbit to Mars. This diagram is for the Mars Exploration Rovers Spirit and Opportunity orbits, launched in 2003, arrived in 2004. Solid planets, Spirit launch and arrival. Ghost planets, Opportunity launch and arrival. Credit NASA/JPL.
07/25/2018 – Ephemeris – The bright planets this week
Ephemeris for Wednesday, July 25th. The Sun rises at 6:21. It’ll be up for 14 hours and 55 minutes, setting at 9:16. The Moon, 2 days before full, will set at 5:13 tomorrow morning.
It’s Wednesday and time to look for and at the bright planets. Three of them are visible in the evening sky. The brilliant beacon of Venus will be visible in the western twilight from about 9:40 p.m. until it sets at 11:07 p.m. Mercury, is now too close to the Sun be seen. Jupiter will be in the south-southwest as it gets dark. It is only outshone by Venus, the Moon, and for a few weeks by Mars at its closest. Jupiter will set at 1:15 a.m. Saturn will start the evening low in the southeast and will stay relatively low, above the Teapot of Sagittarius. It will be due south at 11:45 p.m. and will set at 4:10 a.m.. Mars will rise at 9:49 p.m. and is now only 36.0 million miles (57.9 million km) away. It will reach opposition early Friday morning.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Evening planets from Venus to Saturn plus Moon and the officially morning planet (for two more days) Mars at 10:30 p.m., July 25, 2018. Click on image to enlarge. Created using Stellarium.
The Moon as it might be seen in binoculars this evening. Created using Stellarium.
Venus, Jupiter, Saturn and Mars with the same magnification at 10:30 p.m. July 25, 2018.
Mars is also shown enlarged. It seems that the global dust storm may be abating according to one report I saw on Twitter. Created using Cartes du Ciel (Sky Charts).
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on July 25, 2018. The night ends on the left with sunrise on the 26th. Mars, being close to opposition and very much south of the ecliptic is not in the sky at either sunrise or sunset, I showed a patch of sky with Mars in it in the morning that was below the horizon. Click on the image to enlarge. Created using my LookingUp program.
07/24/2018 – Ephemeris – What about those martian canals
Ephemeris for Tuesday, July 24th. The Sun rises at 6:20. It’ll be up for 14 hours and 57 minutes, setting at 9:17. The Moon, 3 days before full, will set at 4:25 tomorrow morning.
The greatest mystery of the late 19th and early 20th century of Mars was the discovery of fine linear marking seen by visual observers of Mars. They were first reported by an Italian astronomer Giovanni Schiaparelli in 1871 as grooves, canali in Italian. It was turned into canals by the English language newspapers of the day. Canals are artificial constructions. Thus one Percival Lowell of Massachusetts built an observatory in Flagstaff Arizona to observe and map Mars for himself, dying in 1916 still believing in an ancient martian civilization bringing water from the polar caps to the equatorial region by canals in order to survive. Alas, there are no canals. Mars is a barren world, whose secrets we now probe below its red dust.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The source if the images below is the talk “Mars 2018” I gave at the Betsie Valley District Library, July, 20, 2018.
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07/23/2018 – Ephemeris – The importance of Mars in determining the nature of the solar system
Monday, July 23rd. The Sun rises at 6:19. It’ll be up for 14 hours and 59 minutes, setting at 9:18. The Moon, half way from first quarter to full, will set at 3:41 tomorrow morning.
The accurate observational positions of Mars by Tycho Brahe allowed Johannes Kepler in the early 17th century to discover his three laws of planetary motion. Tycho was the last and greatest of the naked eye astronomers. Kepler befriended Tycho who jealously guarded his observations. It was only after his death in 1601 that Kepler took possession of Tycho’s data. Until then it was believed that planets moved with uniform circular motion, even though they didn’t look like it. Astronomers added circle after circle, called epicycles, to attempt to make their system work. Mars was the worst case. Kepler finally determined that Mars, and indeed all the planets, orbited the Sun in elliptical orbits. That was his first law of planetary motion.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The source if the images below is the talk “Mars 2018” I gave at the Betsie Valley District Library, July, 20, 2018.
Tycho and Kepler. Artist for Tycho: Eduard Ender (1822-1883). Artist for Kepler, unknown. Source: Wikipedia.
Mars’ and Earth’s orbits to scale and positions of the Earth and Mars July 20, 2018, one week before opposition. Note that Mars’ orbit is decidedly not circular. Credit my LookingUp program.
Created using Cartes du Ciel (Sky Charts).
Created using Cartes du Ciel (Sky Charts).
07/20/2018 – Ephemeris – Two astronomy events this weekend
Ephemeris for Friday, July 20th. Today the Sun will be up for 15 hours and 5 minutes, setting at 9:21, and it will rise tomorrow at 6:17. The Moon, 1 day past first quarter, will set at 1:57 tomorrow morning.
There are two astronomy events in the Grand Traverse region this weekend, starting tonight with a twilight talk and a star party at the Betsie Valley District Library in Thompsonville. It starts at 8:30 p.m. with a talk about Mars throughout history and how it has fascinated astronomers and the public alike through the ages. After which Jupiter and Saturn will be visible. If cloudy, the talk will go on as scheduled, though the observing part will be rescheduled to a later date. Tomorrow, Saturday there, will be viewing at the Northwestern Michigan College’s Rogers Observatory starting at 9 p.m. Jupiter and Saturn will be featured there too. The Observatory is located south of Traverse City on Birmley road.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
A group of folks out to see the planets with the member’s and society’s telescopes. Credit staff of the Betsie Valley District Library.
Scooter girl checking out the view through the rear finder of the society’s 25″ “Dobinator”. Credit staff of the Betsie Valley District Library.
07/19/2018 – Ephemeris – The Moon passes the evening planets one by one over the next week
Ephemeris for Thursday, July 19th. Today the Sun will be up for 15 hours and 7 minutes, setting at 9:22, and it will rise tomorrow at 6:16. The Moon, at first quarter today, will set at 1:29 tomorrow morning.
The Moon is making its monthly journey around the sky. Tonight it will be west or to the right of Jupiter. Tomorrow night Jupiter will be directly below the Moon. Next Tuesday night Saturn will appear below and left of the Moon. Next Thursday night Mars will appear below and to the left of the Moon. Mars at that time will be actually far south of the Moon, so that event usually doesn’t show in almanacs. Mars, being very close to us is in a part of its orbit that takes it south of the Earth’s orbital plane. We see that plane as the ecliptic or path of the Sun. We see the same situation when Venus is close to the Earth, and it is north or south of the ecliptic. The Moon can pass them without being listed as a conjunction.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Here’s the Moon passing each of the superior evening planets in the 8 days from July 20 to July 27 2018. By the time the Mon will pass Mars it will truly be an evening planet. Mars will be at opposition with the Sun that day. Note that the Moon’s size is exaggerated by a factor of 4 to show its phase at this scale. Created using Stellarium and GIMP.
07/18/2018 – Ephemeris – Our weekly look at the bright planets
Ephemeris for Wednesday, July 18th. Today the Sun will be up for 15 hours and 8 minutes, setting at 9:23, and it will rise tomorrow at 6:15. The Moon, 1 day before first quarter, will set at 1:01 tomorrow morning.
It’s Wednesday and time to look for and at the bright planets. Four of them are in the evening sky. The brilliant beacon of Venus will be visible in the western twilight from about 9:40 p.m. until it sets at 11:21 p.m. Mercury, is fading and is far below and right of Venus, setting at 10:18 p.m. Jupiter will be in the south as it gets dark. It is only outshone by Venus, the Moon, and for a few weeks by Mars at its closest. Jupiter will set at 1:42 a.m. Saturn will start the evening low in the southeast and will stay relatively low, above the Teapot of Sagittarius. It will be due south at 12:14 a.m. and will set at 4:40 a.m.. Mars will rise at 10:20 p.m. and is now only 36.8 million miles (59.2 million km) away, in telescopes it appear to be 23.7″ (seconds of arc) in diameter. It will be due south and at its highest in the sky at 2:35 a.m. at 21 degrees altitude.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Evening planets from Mercury to Saturn and Moon at 9:50 p.m., July 18, 2018. Click on image to enlarge. Created using Stellarium.
Mars at its highest in the south with Saturn at 2:35 a.m. Click on image to enlarge. Created using Stellarium.
The moon as it might be seen in binoculars this evening. Created using Stellarium.
Telescopic view of Jupiter, Saturn and Mars at 11 p.m. on July 18. All at the same magnification. Created using Cartes du Ciel (Sky Charts).
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on July 18, 2018. The night ends on the left with sunrise on the 19th. Click on the image to enlarge. Created using my LookingUp program.
07/17/2018 – Ephemeris – Finding Cygnus the swan
Ephemeris for Tuesday, July 17th. Today the Sun will be up for 15 hours and 10 minutes, setting at 9:24, and it will rise tomorrow at 6:14. The Moon, 2 days before first quarter, will set at 12:32 tomorrow morning
High in the east northeast as it gets dark flies the constellation of Cygnus the swan. This constellation is also known as the Northern Cross. The cross is seen lying on its side with the bright star Deneb at the head of the cross to the left. The rest of the cross is delineated in the stars to the right. As a swan, Deneb is the tail, the stars of the crosspiece of the cross are the leading edges of wings as Cygnus flies south through the Milky Way. There are faint stars that also define the tips and trailing edges of its wings. It is a very good portrayal of a flying swan, like the mute swans we see on the wing. In Cygnus we are looking in the direction that the Sun and the Earth are traveling as we orbit the center of the Milky Way.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Animated Cygnus finder chart. Included also are, beside Deneb, the other stars of the Summer Triangle: Vega and Altair and their constellations Lyra the harp and Aquila. See if you can find them. Created using Stellarium.
07/16/2018 – Ephemeris – Lyra the harp, Hermes’ invention
Ephemeris for Monday, July 16th. Today the Sun will be up for 15 hours and 12 minutes, setting at 9:24, and it will rise tomorrow at 6:13. The Moon, 3 days before first quarter, will set at 12:02 tomorrow morning.
Very high up in the eastern sky at 11 p.m. can be found a bright star just north of a small, narrow, but very distinctive parallelogram of stars. They are the stars of the constellation Lyra the harp. The bright star is Vega, one of the twenty one brightest first magnitude stars. Vega is actually the 5th brightest night-time star. The harp, according to Greek mythology, was invented by the god Hermes. The form of the harp in the sky, is as he had invented it: by stretching strings across a tortoise shell. Hermes gave it to his half-brother Apollo, who in turn gave it to the great musician Orpheus. The Sun has a motion with respect to most stars around it. Its direction is towards the vicinity of Lyra.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addenda
Animated Lyra finder chart. with Vega and the other named stars of the Summer Triangle. The lyre image not supplied by Stellarium but is from The World’s Earliest Music by Hermann Smith, Figure 60, A Project Gutenberg Ebook, and captioned “The Chelys or Greek Tortoiseshell Lyre”. Click on the image to enlarge Created using Stellarium and GIMP.
Last Saturday night’s wild Sun ‘n Star Party
Last Saturday night the Grand Traverse Astronomical Society, myself included, and the rangers and volunteers of the Sleeping Bear Dunes National Lakeshore held our Sun ‘n Star Party at the Dune Climb. I live 20 miles southeast of the Dune Climb, and about half way between Traverse City and Interlochen. It’s also the location for which the Ephemeris sunrise and sunset times are calculated for. We rely on the GOES East satellite imagery to show us the cloud patterns and movement. Saturday morning was pretty overcast and hot. GOES East showed that a big clearing was heading for us. At 1 p.m. I emailed our members that the event was a GO, and began to pack up the car with my two telescopes, and assorted items. Meanwhile some raindrops were showing up on the windshield. A check with weather radar on my phone confirmed that some rainstorms were popping up between my location and Lake Michigan. This is rather normal when it’s hot and humid in the afternoon, and wouldn’t affect the Dune area close to the lake. In driving to the Dune Climb I drove through some rain showers, but the skies cleared by the time I got within 5 miles from the lake.
The solar observing from 4 to 6 p.m.was great, except for no sunspots. We had 2 solar telescopes that did reveal some prominences. The sky was clear. The storm clouds were receding to the east. Of course we couldn’t see much to the west because the dune was in the way. Its angular altitude averaged 12 degrees. Some of us stayed there and ate our dinner. By 7:30 the wind came up from the southwest. A check of the GOES East satellite showed us a large, roughly square cloud the width of the lake slowly moving northward that was just south of us. Just after 8 p.m. we noticed clouds looming from the south, then fog was overtaking the tops of the dunes to the southwest. Shortly thereafter we were socked in. At a little after 9 p.m. Marie Scott the ranger in charge of this event gave introductions, and handed the microphone to me, who introduced our members and went over what we were supposed to see that night. We couldn’t track this cloud anymore by satellite because it was between the daytime color imagery and the nighttime infrared imagery. However around 10 p.m. someone spotted Vega, nearly overhead. And while I was swinging my 11″ Dobsonian towards it, someone else called out Jupiter. Looking around the fog was lifting. The night was salvaged. We stayed over an hour after the official 11 p.m. to watch Mars rise near the end of the star party, and finally view some of the wonders of the dark summer sky.
This was the fourth of seven monthly star parties scheduled at the Dunes this year. It was the first we didn’t cancel due to weather. We generally cancel one or two of then a year, but to start the year with three was depressing.
