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Ephemeris: 04/25/2025 – The star that opened a World’s Fair
This is Ephemeris for Arbor Day, Friday, April 25th. Today the Sun will be up for 13 hours and 59 minutes, setting at 8:40, and it will rise tomorrow at 6:39. The Moon, 2 days before new, will rise at 5:50 tomorrow morning.
High in the eastern sky at 10 tonight can be found the kite shaped constellation of Boötes the herdsman, chasing or herding the Great Bear Ursa Major of which the Big Dipper is the hind end, across the sky. The bright star at the base of the kite is the 4th brightest nighttime star, Arcturus. It can be found and name remembered by first locating the Big Dipper and by following the arc or curve of the handle to Arcturus. This star is an orange-colored giant star, 37 light years away. Its light was used to open the 1933 Chicago Worlds Fair believing its light left the star in 1893 the year of the previous Chicago Worlds Fair. It turns out that Arcturus is 3 light years closer than what they thought.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
For more on how they did it go to: https://chicagology.com/centuryprogress/1933fair54/
Ephemeris: 04/24/2025 – A constellation that’s a queen’s offering of her hair
This is Bob Moler with Ephemeris for Thursday, April 24th. Today the Sun will be up for 13 hours and 56 minutes, setting at 8:39, and it will rise tomorrow at 6:41. The Moon, 3 days before new, will rise at 5:29 tomorrow morning.
High in the east-southeast at 10 p.m. is a tiny and faint constellation of Coma Berenices, or Berenice’s hair. In it are lots of faint stars arrayed to look like several strands of hair. The whole group will fit in the field of a pair of binoculars, which will also show many more stars. The hank of hair was supposed to belong to Berenice, a real Queen of Egypt, of the 3rd century BCE who cut off her golden tresses and offered them to the gods for the safe return of her husband from war. Her husband did return safe, and at that same time her hair disappeared from the temple. The oracle of the temple pointed to this constellation showing that her sacrifice was enshrined in the stars.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/23/2025 – Taking our weekly look at where the naked eye planets have wandered off to
This is Ephemeris for Wednesday, April 23rd. Today the Sun will be up for 13 hours and 53 minutes, setting at 8:38, and it will rise tomorrow at 6:43. The Moon, 3 days past last quarter, will rise at 5:09 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. At 9:30 PM this evening two of the five naked eye planets will be out. Jupiter, is now the brighter evening planet, outshining all the stars, and being our substitute Evening Star, if you will. It will be in the west. Below it is the bright star Aldebaran. To its lower left, the great constellation of Orion. The rapidly fading Mars, with its distinctive reddish hue, is high in the southwest, with the stars Castor and Pollux in Gemini to the right and below it. By 5:30 AM Venus will be seen very low in the east, as the Morning Star. It will require a low eastern horizon to spot it at that hour. It should be visible until a bit after 6:30. Saturn should be visible in the morning by the end of the month.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/21/2025 – Follow the spike to Spica
This is Ephemeris for Monday, April 21st. Today the Sun will be up for 13 hours and 47 minutes, setting at 8:35, and it will rise tomorrow at 6:46. The Moon, 1 day past last quarter, will rise at 4:25 tomorrow morning.
In the south-southeast at 10:30 p.m. is the bright star Spica, which can be found from all the way back overhead to the Big Dipper. Follow the arc of the handle of the Big Dipper to the bright star Arcturus below it in the east-southeast. Then straighten the curve of the arc to a straight spike which points to Spica, the brightest star in Virgo the virgin. Arcturus is much brighter than Spica and has an orange tint to Spica’s bluish hue. In fact, Spica is the bluest of the 21 first magnitude stars. That means that it has a really hot surface temperature. Actually, Spica is really two blue-white stars orbiting each other in 4 days. Spica is 250 light years away. It also was an important star to the ancient Greeks. One temple was built and aligned to its setting point. The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/18/2025 – How the date of Easter is calculated
This is Ephemeris for Good Friday, Friday, April 18th. Today the Sun will be up for 13 hours and 39 minutes, setting at 8:32, and it will rise tomorrow at 6:51. The Moon, 2 days before last quarter, will rise at 2:40 tomorrow morning.
Easter will be celebrated by all Christian churches this Sunday. Easter is a movable feast in that it falls on a different date each year following the first full moon of spring. It’s an attempt to follow the Jewish Passover, which starts on the 15th of the month of Nisan. The Jewish calendar being a lunar calendar, the 15th is generally the night of the full moon. And since the Last Supper was a Seder, according to at least one Gospel, the Christian church wanted to link Easter with Passover as closely as possible using the Roman solar based (Julian) calendar. The months didn’t follow the cycle of the Moon anymore and where the year was 365.25 days long. Passover started at sunset last Sunday. The western churches adopted the Gregorian calendar to keep in sync with the seasons. The Orthodox churches didn’t, but Easter is so late that they match this year. They kept the old Julian Calendar and other considerations to calculate the date of Easter.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/17/2025 – Finding the celestial crow
This is Ephemeris for Thursday, April 17th. Today the Sun will be up for 13 hours and 36 minutes, setting at 8:30, and it will rise tomorrow at 6:52. The Moon, 3 days before last quarter, will rise at 1:48 tomorrow morning.
The small constellation of Corvus the crow is located low in the south-southeast at 10:30 this evening. It’s made of 6 dim stars, but the pattern is a distinctive but distorted box with two stars at the upper left marking that corner, and another two marking the lower right corner. I usually don’t notice the extra star at these corners. To me the box stands out enough. It’s pretty much alone below Virgo and its bright star Spica, left an above it. I don’t see a crow here, but the box is distinctive in that no two sides are parallel. In the US we call the shape a trapezium. The British call it a trapezoid. Anyway it is a very interesting shape, at least to me.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/16/2025 – Taking our weekly look at the naked-eye planets
This is Ephemeris for Wednesday, April 16th. Today the Sun will be up for 13 hours and 33 minutes, setting at 8:29, and it will rise tomorrow at 6:54. The Moon, halfway from full to last quarter, will rise at 12:48 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. At 9:30 PM this evening just two of the five naked eye planets will be out. Jupiter, now becomes the brightest evening planet, our substitute evening star if you will. It will be high in the west. Below it is the bright star Aldebaran. To its lower left, the great constellation of Orion. The rapidly fading Mars, with its distinctive reddish hue, is high in the south-southwest, with the stars Castor and Pollux in Gemini to the right of it. By 6 AM Venus will be seen very low in the east, as the Morning Star. It will require a low eastern horizon. It should be visible until a bit after 6:30. Saturn should be visible in the morning by the end of the month.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/14/2025 – Follow the arc to Arcturus
This is Ephemeris for Monday, April 14th. Today the Sun will be up for 13 hours and 27 minutes, setting at 8:27, and it will rise tomorrow at 6:57. The Moon, 2 days past full, will rise at 10:36 this evening.
The fourth or fifth-brightest nighttime star, depending on whose list you see, is now up in the east in the evening. 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 “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 astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/11/2025 – Thoughts on Starliner and Artemis problems
This is Ephemeris for Friday, April 11th. Today the Sun will be up for 13 hours and 18 minutes, setting at 8:23, and it will rise tomorrow at 7:03. The Moon, 1 day before full, will set at 6:44 tomorrow morning.
As someone who has watched the Apollo program progress, back in the 1960s, and the race to get to the Moon before the Russkies, the Artemis program seems rather sluggish. Most of the reason of course, is because it isn’t enough of a high priority, and we’re trying to do it on the cheap, reusing as much of the ill-fated space shuttle hardware as possible. NASA is gun shy about putting astronauts into danger, when they don’t have to. The Apollo 1, and two Space Shuttle accidents is the main reason that Butch and Suni didn’t ride back to Earth in their ailing Starliner capsule. The Starliner capsule is built by the same company, Boeing, who is prime contractor on the main stage of the moon rocket. Both have experienced long delays, and quality issues.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 04/10/2025 – Saturn is soon going to emerge from the morning twilight
This is Ephemeris for Thursday, April 10th. Today the Sun will be up for 13 hours and 15 minutes, setting at 8:22, and it will rise tomorrow at 7:04. The Moon, 2 days before full, will set at 6:29 tomorrow morning.
The planets that have transitioned from the evening sky to the morning sky are beginning to show up in the morning now as they separate themselves from the Sun. Venus is the first to appear low in the east starting about 6:00 in the morning. Saturn will be very near Venus and below right of it on the 28th of this month. Saturn will separate itself more and more from the Sun over the spring and summer months until in late September when it becomes, officially, an evening planet again. Venus will increase its separation from the Sun until May 31st, its greatest separation from the sun of 46°. Then it will slowly head back towards the direction of the Sun. However, it will stay in the morning sky for the rest of the year.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
On the 28th, both planets will be at the same distance west of the sun in right ascension, which is the same as longitude in the Earth’s coordinate system. The two planets were a bit closer on the 25th. Saturn is just a little bit less than three degrees above the horizon in the above image. One needs a low eastern horizon to spot it. Saturn may be visible a few days before that, however it is lacking a bright ring right now. The Earth passed through the Saturn’s ring plane on March 23rd, and we are now looking at, probably, a thin line through the planet. The ring should be fairly dim because the Sun is shining on the other side of the rings, and will until its crossover on May 6th.
Bob Moler's Ephemeris Blog 
