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Ephemeris: 11/20/2024 – Our weekly look at the naked-eye planets

November 20, 2024 Comments off

This is Ephemeris for Wednesday, November 20th. Today the Sun will be up for 9 hours and 22 minutes, setting at 5:09, and it will rise tomorrow at 7:48. The Moon, 2 days before last quarter, will rise at 9:45 this evening.

Let’s take our weekly look at the whereabouts of the naked-eye planets. Venus can be spotted low in the southwestern sky by 5:30 PM, about 20 minutes after sunset. It will set at 7:41. Saturn will be in the south-southeast at 6 PM. Jupiter will rise at 6:11 PM in the east northeast, and be a good object for the small telescope about an hour later. Mars, rises tonight near 9:36, just ahead of the Moon and will be leading it through the night skies tonight. By 6:00 AM tomorrow Jupiter will be in the west, above and right of Orion, while reddish Mars will be high in the southwest to the right of the waning gibbous Moon. Jupiter and Saturn are good planets to view with a small telescope, Mars will appear only a quarter the diameter of Jupiter.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

Venus will appear in the south-southwest at about 5:30 PM or about 20 minutes after sunset
This is where Venus will appear in the south-southwest at about 5:30 PM or about 20 minutes after sunset. Venus is now in the part of the ecliptic where the planets travel northward as it moves eastward. So It will be seeing it higher in the sky when it’s first spotted in the evening. Created using Stellarium.
Saturn finder animation
Saturn and the star Fomalhaut as they would appear at 8 PM this evening in the south. This is a chart from yesterday’s post. There is no real change from then. Created using Stellarium and GIMP.
A finder animation for Jupiter, Mars and the Moon
A finder animation for Jupiter, Mars and the Moon for 10:30 PM this evening, November 20, 2024. They’re located among the winter constellations that are rising in the late evening. We are a month and a day from the beginning of winter. Created using Stellarium and GIMP.
The Moon as it might appear through a small telescope tonight
The Moon as it might appear through a small telescope tonight, November 20, 2024. Selected features are labeled. Created using Stellarium, LibreOffice draw, and GIMP.
Telescopic Venus, Saturn, Jupiter and Mars
Telescopic Venus, Saturn, Jupiter and Mars (north up) as they would be seen in a small telescope with the same magnification. All the planets are shown for tonight, November 20, 2024 at 11 PM EST. Apparent diameters: Venus 16.0″, 71.1% illuminated; Saturn 17.8″, its rings 41.3″, 5.2 degrees from edge on (starting to close again); Jupiter 47.8″; Mars, 10.7″, 91.0% illuminated. Saturn’s rings are actually much brighter than depicted here. Planetary surface detail is more subtle than shown here. Jupiter’s moon Ganymede is behind the planet, but will appear on the Io and Eurolpa side of the planet at 11:16 PM. The ” symbol means seconds of arc, or 1/3600th of a degree. Click or tap on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on November 20, 2024. The night ends on the left with sunrise on the 21st. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
Low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow
This is a low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow, November 20 and 21, 2024. Some of the columns are self-explanatory, others not. The transit column is the time that the body crosses the meridian and is due south. Elong, for elongation, is the angle between the Sun and that body. RA is right ascension, which is the object’s east-west position on the celestial sphere in hours and minutes. Dec is declination which is the north-south position of the object on the celestial sphere in degrees and minutes. R is the distance of that object from the Sun in astronomical units. An astronomical unit is about 93 million miles or 150 million kilometers. And Delta is the distance of that object from the Earth, also in astronomical units. I omit the ‘m’ in am and pm for compactness. The data was generated using my LookingUp for DOS app and displayed as a table by my Ephemeris Helper app.
Categories: Ephemeris Program, Naked-eye planets, Observing, Planets Tags: , , , ,

Ephemeris: 11/19/2024 – The loneliest star in the sky

November 19, 2024 Comments off

This is Bob Moler with Ephemeris for Tuesday, November 19th. Today the Sun will be up for 9 hours and 24 minutes, setting at 5:10, and it will rise tomorrow at 7:47. The Moon, 3 days before last quarter, will rise at 8:32 this evening.

There’s a bright star that appears for only seven and a half hours on autumn evenings. Its appearance, low in the south-southeast at 8 p.m., is a clear sign that autumn is here. It is currently far below the much brighter Saturn. The star’s name is Fomalhaut, which means fish’s mouth. That’s fitting because it’s in the constellation of Piscis Austrinus, the southern fish. At our latitude it’s kind of the fish that got away, because usually Fomalhaut appears to be quite alone low in the sky. For the last few years Jupiter and then Saturn have kept it company. In a couple of years Saturn will have moved on leaving Fomalhaut to its lonely vigil in the south.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

A Fomalhaut finder chart in four frames
A Fomalhaut finder chart in four frames, showing just the stars and the planet Saturn; Saturn and Fomalhaut labeled; the constellation outlined and labeled; and lastly, the fish as imagined by the Stellarium artist.. For 8 PM this evening, November 19 2024. Created using Stellarium and GIMP.

Categories: Ephemeris Program, Observing, Stars Tags: ,

Ephemeris: 11/18/2024 – How to get two spacecraft to come together gently in space

November 18, 2024 Comments off

This is Bob Moler with Ephemeris for Monday, November 18th. Today the Sun will be up for 9 hours and 26 minutes, setting at 5:11, and it will rise tomorrow at 7:45. The Moon, 3 days past full, will rise at 7:22 this evening.

Orbital mechanics is a science of how orbits work around the Earth, Sun, or any other body. Back in the mid 1960s when NASA was starting it’s work to get to the Moon with the Gemini program they had quite a time getting rendezvous and docking right. Buzz Aldrin, the second man to step foot on the Moon, who is still around by the way, figured it all out – before he became an astronaut. It’s counter-intuitive. To speed up you slow down to drop into a lower orbit which is faster. To slow down, speed up and climb into a higher orbit which slows you down. There’s more to it than that, but basically objects in orbit just don’t seem to behave the way you think they ought to. And that’s how things work in space.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

Rendezvous and Docking diagram
Rendezvous and Docking diagram from Caroline Elizabeth Specht,German Aerospace Center (DLR) | DLR · Institute of Robotics and Mechatronics via ResearchGate.net. Description below.

In this diagram time is represented on the horizontal axis from right to left, the altitude of the spacecraft and its target is on the vertical axis. The chaser vehicle is launched as the launch site crosses the plane of the orbit of the target. Changing the plane of an orbit is very expensive, energywise, so it’s best to launch in the same orbital plane. It enters an elliptical orbit, most initial orbits are pretty elliptical and so there’s a low point, or perigee, where the chaser enters orbit, and a high point which is the apogee. This is below the target orbit so that the chasing vehicle can catch up to the target. Lower orbits are faster than higher orbits, this is the phasing part. When the chaser gets pretty close it raises its orbit so that the starting point apogee is the new perigee and the new apogee is the altitude of the orbit of the target. The orbit stays elliptical for a little while so that the chasing spacecraft can slowly catch up to the target. In the final approach the orbits just about match so that the chaser very slowly catches up to the target.

I’ve seen similar diagrams on NASA broadcasts of Crew Dragon launches.

Categories: Concepts, Ephemeris Program, Space Flight

Ephemeris: 11/15/2024 – What causes the tides?

November 15, 2024 Comments off

This is Ephemeris for Friday, November 15th. Today the Sun will be up for 9 hours and 33 minutes, setting at 5:14, and it will rise tomorrow at 7:41. The Moon, at full today, will rise at 4:48 this evening.

Today, at full moon, is one of the two highest tides of the month, the lunar month that is. The other highest tide comes at new moon. Both the Moon and the Sun cause tides because of their gravitational pull on the Earth. At new and full moon’s their gravitational pull gangs up on us. Since Earth is not a point body the gravitational pull of an object on the near side of the Earth pulls harder than it does on the opposite side of the Earth. Gravitational force diminishes with the square of the distance so it is the difference in the gravitational pull from one side to the other of the Earth that causes the tides to rise up on the side nearest and farthest from the gravitational pull of the moon and/or Sun. Since the Earth has a worldwide ocean, the water is free to slosh around and cause the tides.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

Spring and Neap Tides explained.
Spring and Neap Tides explained. Credit http://www.millerslocal.co.za/the-inside-skinny-on-tides.html (South Africa).
Categories: Concepts, Earth, Ephemeris Program, Tides Tags: , ,

Ephemeris: 11/14/2024 – SpaceX to deorbit the International Space Station

November 14, 2024 Comments off

This is Ephemeris for Thursday, November 14th. Today the Sun will be up for 9 hours and 35 minutes, setting at 5:15, and it will rise tomorrow at 7:40. The Moon, 1 day before full, will set at 7:28 tomorrow morning.

SpaceX has received a contract from NASA to deorbit the International Space Station around the year 2030. The contract is for a little bit less than a billion dollars. SpaceX will develop a special Dragon capsule with enough fuel to deorbit the space station. The idea is to drop the space station’s orbit over a period of months and guided in its final journey to a spot in the South Pacific Ocean called Point Nemo, which is the spot between New Zealand and Chile near longitude 120° W and latitude 50° South. Point Nemo is named after the captain of the fictional submarine Nautilus from the Jules Verne novel 20,000 Leagues Under the Sea. Point Nemo is the farthest point in the South Pacific Ocean from any landmass: island or continent.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

What the special SpaceX Cargo Capsule and Trunk might look like
Image of what the special SpaceX Cargo Capsule and Trunk might look like as it deorbits the International Space Station. Credit: SpaceX.
Categories: Ephemeris Program, NASA Tags: , ,

Ephemeris: 11/13/2024 – Looking for the naked-eye planets this week

November 13, 2024 Comments off

This is Ephemeris for Wednesday, November 13th. Today the Sun will be up for 9 hours and 38 minutes, setting at 5:16, and it will rise tomorrow at 7:39. The Moon, 2 days before full, will set at 6:03 tomorrow morning.

Let’s take our weekly look at the whereabouts of the naked-eye planets. Venus can be spotted low in the southwestern sky by 6 PM, about 45 minutes after sunset. It will set at 7:30. Saturn will be in the south-southeast at 7 PM. Jupiter will rise at 6:42 PM in the east northeast, and be a good object for the small telescope about an hour later. By 6:00 AM tomorrow Jupiter will be high in the west, above and right of Orion, while reddish Mars, which rises tonight near 9:56, will be high in the south-southwest. Jupiter and Saturn are good planets to view with a small telescope, while Venus and Mars will appear very small and featureless. These last two will improve next year when they move closer to us.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

Venus as it might appear tonight at 6 PM, about 45 minutes after sunset, low in the southwest. Venus is now as far South in the sky as it will get and will now begin to move northward. From now until the end of the year it will rise higher and higher in the sky in the evening. Its greatest eastern separation, or elongation, from the Sun will occur on January 2nd. Created using Stellarium.
Saturn, the Moon with Jupiter rising at 7 PM. Off to the right beyond the image, Venus setting in the southwest. Click or tap on the image to enlarge it. Created using Stellarium.
The Moon as it might appear through a small telescope tonight, November 13, 2024. Selected features are labeled. Created using stellarium, LibreOffice draw, and GIMP.
Jupiter and Mars among the stars of winter seen in the southwestern sky at 6 AM, or about an hour and a half before sunrise, tomorrow morning November 14, 2024. Created using Stellarium.
Telescopic Venus, Saturn, Jupiter and Mars (north up) as they would be seen in a small telescope with the same magnification. All the planets except Mars are shown for tonight, November 13, 2024, Mars for tomorrow morning the 14th. Apparent diameters: Venus 15.3″, 73.3% illuminated; Saturn 18.0″, its rings 41.9″, 5.3 degrees from edge on (starting to close again); Jupiter 47.4″; Mars, 10.2″, 90.1% illuminated. Saturn’s rings are actually much brighter than depicted here. Plan etary surface detail is more subtle than shown here. The ” means seconds of arc, or 1/3600th of a degree. Click or tap on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on November 13, 2024. The night ends on the left with sunrise on the 14th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
This is a low precision ephemeris of the Sun Moon and naked eye planet positions for today and tomorrow, November 13 and 14, 2024. Some of the columns are self-explanatory, others not. The transit column is the time that the body crosses the meridian and is due south. Elong, for elongation, is the angle between the Sun and that body. RA is right ascension, which is the object’s east-west position on the celestial sphere in hours and minutes. Dec is declination which is the north-south position of the object on the celestial sphere in degrees and minutes. R is the distance of that object from the Sun in astronomical units. An astronomical unit is about 93 million miles or 150 million kilometers. And Delta is the distance of that object from the Earth, also in astronomical units. I omit the ‘m’ in am and pm for compactness. The data was generated using my LookingUp for DOS app and displayed as a table by my Ephemeris Helper app.
Categories: Ephemeris Program, Naked-eye planets, Observing, Planets

Ephemeris: 11/12/2024 – SpaceX uses Cargo Dragon to change orbit of the ISS

November 12, 2024 Comments off

This is Bob Moler with Ephemeris for Tuesday, November 12th. Today the Sun will be up for 9 hours and 40 minutes, setting at 5:17, and it will rise tomorrow at 7:37. The Moon, halfway from first quarter to full, will set at 4:39 tomorrow morning.

After the last SpaceX cargo mission arrived at the International Space Station, they used the thrusters on the SpaceX capsule to raise the orbital space station a little bit as a test. SpaceX capsules dock at the forward end of the space station according to direction of travel so in order to boost the station’s orbit they had to flip the station around so that the docking port was at the rear before they could apply the needed thrust. When thrust is applied to an object in orbit the effect of the change occurs mostly at the opposite side of the orbit. In order to permanently raise or lower an object’s circular orbit one must make 2 adjustments 180° away from each other. This is the essence of the Hohmann Transfer Orbit, proposed by German scientist Walter Hohmann in 1925.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations

Addendum

Hohmann Transfer Orbit
Hohmann Transfer Orbit (2) moving, in this case. from one circular orbit (1) to a higher one (3). Moving from point a to point b. The triangle symbol is the Greek capital letter delta, which means change. It reads as delta V, or change in velocity. Image credit: Leafnode based on image by Hubert Bartkowiak in Wikimedia Commons with a and b points added by this author.

Categories: Concepts, Ephemeris Program Tags: , , ,

Ephemeris: 11/11/2024 – Still waiting for the promised nova

November 11, 2024 Comments off

This is Ephemeris for Veterans Day, Monday, November 11th. Today the Sun will be up for 9 hours and 43 minutes, setting at 5:18, and it will rise tomorrow at 7:36. The Moon, 2 days past first quarter, will set at 3:19 tomorrow morning.

We’ve been waiting all year so far for the appearance of a nova or Blaze Star, as they called it, in the constellation of Corona Borealis. The astronomical name For it is T Coronae Borealis or T CrB for short. It last erupted in 1946 and the time before that it was 1866 an interval of 80 years. This year would be 78 years since 1946 so we could be waiting another two years. Observations of the star, which is still visible, though faint, between eruptions, were not as comprehensive in the prior 80 years, as they are today. It’s possible that observations of pre-nova activity were missed during war years preceding the 1946 outburst.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

A Finder for the location of the nova, or Blaze Star, T Coronae Borealis or T CrB (when it happens), for the early evening now
A Finder for the location of the nova, or Blaze Star, T Coronae Borealis or T CrB (when it happens), for the early evening now. Corona Borealis is a small horseshoe shaped constellation whose brightest star Alphecca is just above the “n” in Corona. It is a second magnitude star about the same brightness as the nova will get at its peak. After late November the best time to see the nova, if it occurs then, will be in the morning sky just before sunrise. Though the nova is not circumpolar, meaning it rises and sets, it is up in the sky for 16 of the 24 hours of the day, so we will never completely lose it to daylight. When the Nova explosion occurs it will be visible to the naked eye for about a week so it’s easy to miss in time and also, in Northern Michigan due to the winter weather, we could miss it because of clouds. But as I mentioned in the program script above we are currently about two years away from the nominal time between between explosions, so we still have a couple of years to go before 80 years are up. Created using Stellarium, and LibreOffice Draw.
Categories: Ephemeris Program, Nova, Observing Tags: ,

Ephemeris: 11/08/2024 – The Jade Rabbit on the Moon

November 8, 2024 Comments off

This is Bob Moler with Ephemeris for Friday, November 8th. Today the Sun will be up for 9 hours and 50 minutes, setting at 5:21, and it will rise tomorrow at 7:32. The Moon, 1 day before first quarter, will set at 11:24 this evening.

Tonight’s Moon is just a few hours before the instant of first quarter which is officially at 12:56 tomorrow morning. The ancient Chinese saw in the gray areas of the Moon, we call seas, a rabbit, a pet of Chinese moon goddess Chang’e, its name was Yutu. These have become the names of the Chinese lunar landers and rovers. The top half of that rabbit is visible in the gray areas called maria, or seas. Early telescopic astronomers thought they were actually water filled basins. It turned out to be lava plains, actually floors of huge craters, from asteroids that hit the Moon 4 billion years ago during the late heavy bombardment. The top body of the rabbit is at the top part of the moon it descends to the lower right with his head and ears. The rabbit is also known as the Jade Rabbit. The rest of him is visible when the moon is full. Yutu has a real presence on the Moon, as the names of the two Chinese rovers that landed on the Moon.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

The top part of the Jade Rabbit, as I imagine it upside down, superimposed on tonight's nearly first quarter Moon
The top part of the Jade Rabbit, as I imagine it upside down, superimposed on tonight’s nearly first quarter Moon. Created using Stellarium, LibreOffice Draw, and GIMP.

Categories: China, Ephemeris Program, Observing, The Moon Tags: , , ,

Ephemeris: 11/07/2024 – The Moon wobbles from Earth’s point of view

November 7, 2024 Comments off

This is Ephemeris for Thursday, November 7th. Today the Sun will be up for 9 hours and 53 minutes, setting at 5:22, and it will rise tomorrow at 7:31. The Moon, 2 days before first quarter, will set at 10:08 this evening.

The nearly seven day old Moon appears very low in the southwestern sky tonight. It appears as a fat crescent. The small sea called Mare Crisium or Sea of Crises, near the west edge of the Moon is a good indicator of what we call libration, that is the Moon’s slow wobbling back and forth over the month as it orbits the Earth. One can judge the amount of libration by the distance of that small round sea from the edge of the Moon. This happens because the Moon’s rotation is steady while its orbital velocity around the Earth is not, because its orbit is slightly elliptical. So sometimes the rotation gets ahead of its revolution about the Earth, and sometimes it’s behind. Right now that libration is pushing that small sea towards the edge of the Moon.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.

Addendum

Moon's libration animation
Simulation of the Moon’s distance, phase and libration for October 2007 by Tomruen. Image is in the Public Domain.
Categories: Concepts, Ephemeris Program, Observing, The Moon Tags: