Archive
08/10/2021 – Ephemeris – Tomorrow night, all night, will see the peak of the Perseid Meteor Shower.
This is Bob Moler with Ephemeris for Tuesday, August 10th. Today the Sun will be up for 14 hours and 16 minutes, setting at 8:55, and it will rise tomorrow at 6:40. The Moon, 2 days past new, will set at 10:27 this evening.
Back before astronomers recognized the major meteor shower that occurs at this time of year, the streaks of light in the sky of “falling” or “shooting” stars were called, by Christians, the Tears of Saint Lawrence, who was martyred on this day in the year 258. The bits of comet debris ranging in size from the size of sand grains to that of a pea hit our atmosphere at 38 miles (59 kilometers) per second and quickly vaporize due to friction, causing the streak of light we call meteors. They are called the Perseids since they appear to come from the constellation of Perseus, located in the northeastern sky. They will be best seen tomorrow night and into Thursday morning, with rates of up to one a minute, on average, in the early morning hours.
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
Perseid Radiant finder automation for midnight, August 11th. Created using Stellarium and GIMP.
My best Perseid photo. From the 70s. The stars are trailed because this is a time exposure of perhaps 15 minutes and the camera is on a fixed tripod which rotates with the Earth.
08/09/2021 – Ephemeris – The Perseid Meteors are coming!
This is Ephemeris for Monday, August 9th. Today the Sun will be up for 14 hours and 18 minutes, setting at 8:57, and it will rise tomorrow at 6:39. The Moon, 1 day past new, will set at 10:03 this evening.
If you’ve been out and about under the dark night skies in the last week or so, you may have spotted a few, what are sometimes called, falling or shooting stars. If these could be traced back to the northeastern sky, those were advance members of the Perseid Meteor Shower. The peak of the shower will be on the afternoon of Thursday the 12th, so actually the best time to see them will be in the early hours of that morning. With few exceptions, the best time to view meteors in general or a meteor shower is in the wee morning hours. The Perseids however favor us, because the point from which they seem to come, called the radiant, is so far north that it never sets for us, so they can be seen all night. In the evening, there are just fewer of them.
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
Perseid fireballs in one of NASA’s all sky cameras during the morning hours of August 13, 2017. This is a long time exposure. The bright swath in the image is the Moon that morning. Since it is a time exposure, the radiant is also moving with the earth’s rotation, so the meteors only seem to come from the northeastern sky. North is at the top, and East is to the left. Credit NASA.
08/04/2021 – Ephemeris – Let’s search for the naked-eye planets for this week
This is Bob Moler with Ephemeris for Wednesday, August 4th. Today the Sun will be up for 14 hours and 31 minutes, setting at 9:04, and it will rise tomorrow at 6:33. The Moon, halfway from last quarter to new, will rise at 3:16 tomorrow morning.
Let’s search for the naked-eye planets for this week. Venus can be spotted low in the western twilight by 9:45 pm. It will set at 10:29 pm. Venus will be spending the rest of summer low in the western sky, and not be as conspicuous as it usually is as the Evening Star. Mars is to faint and close to the Sun to be seen from northern latitudes. Saturn, now officially an evening planet, rises before sunset. It will be seen low in the southeast in the evening. Brighter Jupiter will rise at 9:38 pm in the east-southeast and will be seen thereafter trailing Saturn to it’s left or east. Jupiter will join Saturn as an evening planet on the 19th when it too reaches opposition from the Sun.
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
Venus in evening twilight at 9:45 pm, or about 40 minutes after sunset tonight, August 4, 2021. Created using Stellarium.
Jupiter and Saturn in the Southeastern sky at 10;30 pm tonight, August 4, 2021. Created using Stellarium.
The waning crescent Moon as it might be seen in binoculars tomorrow morning at 6 am, about an half an hour before sunrise. Created using Stellarium.
Telescopic view of the bright planets (north up) as they would be seen in a small telescope, with the same magnification, this evening, August 4, 2021. Apparent diameters: Venus, 12.93″; Saturn 18.60″, its rings 43.32″; Jupiter, 48.71″. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
Note on Jupiter and its moons. The Great Red Spot will be visible on the face of Jupiter. Europa will end its transit of the planet around 11:00 pm (03:00 UT on the 5th) Io will be occulted by Jupiter (behind the planet) in the early evening until about 11:27 pm (03:27 UT on the 5th) and will appear to the east of the planet.
Planets and the Moon at sunset and sunrise of a single night, starting with sunset on the right on August 4, 2021. The night ends on the left with sunrise on the 5th. Click on the image to enlarge. Created using my LookingUp program.
08/03/2021 – Ephemeris – Centaur or Teapot?
This is Ephemeris for Tuesday, August 3rd. Today the Sun will be up for 14 hours and 33 minutes, setting at 9:05, and it will rise tomorrow at 6:32. The Moon, 3 days past last quarter, will rise at 2:31 tomorrow morning.
In the south and low in the sky at 10:30 p.m. is one of my favorite asterisms the Teapot of the constellation Sagittarius. Sagittarius classically represents a centaur with a bow and arrow aimed at the heart of the constellation Scorpius to its west. I can find the bow and arrow here, but the half man, half horse figure of the centaur eludes me. However, the stout little teapot of the children’s song is quite obvious, with its base, lid on top, handle to the left and the spout to the right. To make things more realistic, the bright Milky Way seems to rise like steam from its spout. As the night goes on, the Teapot slides westward and appears to tilt, pouring its tea on the southwestern horizon. Its appearance in the south is an invitation to explore the milky band with binoculars.
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
Sagittarius and the Teapot finder animation for tonight, August 3rd. Created using Stellarium.
07/29/2021 – Ephemeris – Anishinaabe constellation of their hero
This is Bob Moler with Ephemeris for Thursday, July 29th. Today the Sun will be up for 14 hours and 45 minutes, setting at 9:11, and it will rise tomorrow at 6:27. The Moon, 2 days before last quarter, will rise at 12:17 tomorrow morning. | Tuesday I talked about the constellation Scorpius the scorpion now seen low in the southern sky in the evening. To me, the stars here make a very good scorpion. Scorpius was invented by people of the Middle East, where scorpions are plentiful. The Anishinaabe native peoples of our area, however, saw one of their legendary hero figures, Nenabozho*. In the sky, the arc of three stars at the front of the scorpion and to the right of the bright star Antares is his bow. He is shooting an arrow toward the receding Great Panther or Curly Tail a constellation of spring whose curl of a tail is the head of the constellation Leo, now lost in the evening twilight in the west. Nenabozho was a hero in their creation stories, a trickster who was often seen as a rabbit.
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.
Addenda
* Nenabozho is pronounced like Nana-bouz-hou, though different tribes pronounced it differently. I could not find Nenabozho and its various other transliterations, one of which was Nanaboozhoo in the Ojibwe People’s Dictionary (https://ojibwe.lib.umn.edu/). However, since he occasionally shape-shifted into being a rabbit his name includes a part of the name for rabbit, waabooz. That entry had several audio examples. That’s how I got the pronunciation for the radio program.
Finder chart
Animated finder for the Anishinaabe constellation of Nenabozho showing the unannotated star field, the Western constellation of Scorpius and Nenabozho. Created using Stellarium (both star lore images are embedded in Stellarium). The Anishinaabe image is embedded in Stellarium and is from Ojibwe Giizhig Anung Masinaaigan – Ojibiwe Sky Star Map created by A. Lee, W. Wilson, and C. Gawboy.
07/28/2021 – Ephemeris – Searching for the naked-eye planets on the last Wednesday in July
This is Ephemeris for Wednesday, July 28th. Today the Sun will be up for 14 hours and 48 minutes, setting at 9:13, and it will rise tomorrow at 6:25. The Moon, 3 days before last quarter, will rise at 11:58 this evening.
Let’s search for the naked-eye planets for this week. Venus can be spotted low in the west-northwest twilight by 9:45 pm. It will set at 10:39 pm. Venus will be spending the rest of summer low in the western sky, and not be as conspicuous as it usually is as the Evening Star. Mars, I believe, is too faint and close to the Sun to be seen from northern latitudes. Saturn will be seen low in the southeast in the evening, with Jupiter rising later. Saturn, 5 days from opposition, that is being opposite the Sun in the sky and closest to Earth, will rise at 9:21 pm. Brighter Jupiter will rise at 10:12 pm, both planets will rise in the east-southeast. By 5:30 am, these two planets will be in the southwestern sky in the morning twilight.
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
Venus in evening twilight in the west at 10 pm, July 28, 2021. Created using Stellarium.
Jupiter and Saturn low in the southeast at 11 pm. Created using Stellarium.
The waning gibbous Moon as it might be seen in binoculars or small telescope at 5:30 am, July 29, 2021. Created using Stellarium.
Telescopic view of the bright planets (north up) as they would be seen in a small telescope, with the same magnification, this evening, July 28, 2021. Apparent diameters: Venus, 12.58″; Saturn 18.59″, its rings 43.31″; Jupiter, 48.28″. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. 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 28, 2021. The night ends on the left with sunrise on the 29th. Click on the image to enlarge. Created using my LookingUp program.
07/26/2021 – Ephemeris – Albireo, a colorful double star in Cygnus the swan
This is Ephemeris for Monday, July 26th. Today the Sun will be up for 14 hours and 52 minutes, setting at 9:15, and it will rise tomorrow at 6:23. The Moon, 3 days past full, will rise at 11:15 this evening.
Alberio is the name given to the star that is in the beak of the constellation of Cygnus the swan, which is high in the east these evenings. It is also at the foot of the asterism or informal constellation of the Northern Cross. To the naked eye Alberio looks like a single star, however even in small telescopes* its true nature is revealed. It is a double star whose individual star colors are strikingly different Its brightest star is yellow, and the dimmer star is blue. While star colors are subtle, these two, due to their apparent closeness, make an obvious color contrast. Unlike what your interior decorator says: In stars blue is hot, yellow, orange and red are cool. Also, it turns out that Alberio’s component stars don’t orbit each other. It is what is called an optical double. The blue star is a bit farther away than the yellow one, though they’re both around 430 light years away.
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.
* It will take at least about 20 power magnification to split. Binoculars won’t do it.
Addendum
Animated Albireo finder chart. Albireo is located in the head of Cygnus the swan, or at the base of the Northern Cross. Tagged stars are, beside Albireo, the stars of the Summer Triangle: Deneb, Vega and Altair plus the star at the junction of the upright and crosspiece of the cross, Sadr. Created using Stellarium.
Albireo, captured at high magnification by the staff of the Smithsonian Institution.
07/19/2021 – Ephemeris – How does your telescope’s image orientation compare to how it looks to the naked-eye?
This is Ephemeris for Monday, July 19th. Today the Sun will be up for 15 hours and 6 minutes, setting at 9:22, and it will rise tomorrow at 6:16. The Moon, 2 days past first quarter, will set at 2:35 tomorrow morning.
When you look through a telescope at the Moon, how does it look compare to how it looks to the naked-eye? Yes, it’s bigger and probably brighter. But how did its orientation change? Astronomical telescopes generally give an upside-own image, that is rotated 180 degrees. Newtonian reflector telescopes, with their eyepiece near the top of the telescope, give such an image, as do refractor telescopes where the diagonal mirror near the eyepiece is not used. When such a mirror is used a right side up, but mirror image is the result. The mirror image results when an odd number of reflections occur in the light path. Binoculars use two or four reflections. Newtonian reflectors have two reflections. It can be confusing sometimes.
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
07/16/2021 – Ephemeris – The best time to see detail on the Moon (IMHO)
This is Ephemeris for Friday, July 16th. Today the Sun will be up for 15 hours and 11 minutes, setting at 9:24, and it will rise tomorrow at 6:13. The Moon, 1 day before first quarter, will set at 1:08 tomorrow morning.
I consider the week centered on the first quarter moon to be the best time to view the Moon in a telescope. The best part of the Moon to view is near the terminator. The terminator is the sunrise line on the moon that we see before full moon, and the sunset line we see after full moon. The terminator is where the shadows are longest on the Moon and indeed on the Earth, with the low Sun in the sky. The Moon has lots of craters in its south or bottom part. We call that the lunar highlands, which is completely saturated with craters. Personally, I like craters. The darker lava plains that were initially called seas (the name stuck). They are flat and nearly featureless unless seen very close to the terminator, where the slight wrinkle ridges can be spotted.
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
The Moon tonight at 11 pm, July 16, 2021, about a day and 7 hours before the instant of first quarter. Note the shadows that bring out the craters near the terminator. Created using Stellarium.
Wrinkle ridges on the floor of a lunar sea (lava plain). These are only visible at a very low sun angle near the terminator. I can find no information on this image, but apparently it was taken in lunar orbit. This is much sharper detail than can be seen from earth.
07/09/2021 – Ephemeris – Finding the constellation of Aquila the eagle
This is Ephemeris for Friday, July 9th. Today the Sun will be up for 15 hours and 22 minutes, setting at 9:29, and it will rise tomorrow at 6:07. The Moon is new today, and won’t be visible.
Aquila the eagle is a constellation that lies in the Milky Way. It’s in the southeastern sky as it gets dark. Its brightest star, Altair, is one of the stars of the Summer Triangle, a group of three bright stars dominating the eastern sky in the evening now. Altair, in the head of the eagle, is flanked by two slightly dimmer stars, the shoulders of the eagle. The eagle is flying northeastward through the Milky Way. Its wings are seen in the wing tip stars. A curved group of stars to the lower right of Altair is its tail. Within Aquila, the Milky Way shows many dark clouds as part of the Great Rift that splits it here. The other summer bird is Cygnus the swan above and left of Aquila, flying in the opposite direction. It was said this was the eagle that attended the god Jupiter.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4). They may be different for your location.
Addendum
Animated Cygnus finder chart. Lyra the harp, Cygnus the swan, Delphinus the dolphin and Sagitta the arrow are also in the image. Can you find them? Click on the image to enlarge it. Created using Stellarium and GIMP.
